Exam-Oriented Anatomy: Questions and Answers, Vol 2 [2 ed.]

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Volume 2

Exam-Oriented

Anatomy Questions and Answers Second Edition  

General Embryology Abdomen

Shoukat N Kazi

 

Genetics Pelvis

MS (Anatomy), DTCD, BSc, LLB

Principal, Dr Tasgaonkar Medical College and Research Centre, Karjat, Maharashtra Ex-Principal, Prasad Institute of Medical Sciences Banthara, Lucknow (UP) Ex-Professor Rajshree Medical Research Institute, Bareilly SRM Medical College Hospital and Research Centre, Potheri, Chennai Chennai Medical College Hospital and Research Centre, Trichy Dr DY Patil Medical College, Pimpri, Maharashtra Dr DY Patil Vidyapeeth (Deemed to be University), Pimpri, Pune

CBS Publishers & Distributors

Pvt Ltd

New Delhi • Bengaluru • Chennai • Kochi • Kolkata • Mumbai Hyderabad • Jharkhand • Nagpur • Patna • Pune • Uttarakhand

Disclaimer Science and technology are constantly changing fields. New research and experience broaden the scope of information and knowledge. The authors have tried their best in giving information available to them while preparing the material for this book. Although, all efforts have been made to ensure optimum accuracy of the material, yet it is quite possible some errors might have been left uncorrected. The publisher, the printer and the authors will not be held responsible for any inadvertent errors, omissions or inaccuracies. eISBN: xxxx Copyright © Authors and Publisher Second eBook Edition: 2021 All rights reserved. No part of this eBook may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system without permission, in writing, from the authors and the publisher. Published by Satish Kumar Jain and produced by Varun Jain for CBS Publishers & Distributors Pvt. Ltd. Corporate Office: 204 FIE, Industrial Area, Patparganj, New Delhi-110092 Ph: +91-11-49344934; Fax: +91-11-49344935; Website: www.cbspd.com; www.eduport-global.com; E-mail: [email protected]; [email protected] Head Office: CBS PLAZA, 4819/XI Prahlad Street, 24 Ansari Road, Daryaganj, New Delhi-110002, India. Ph: +91-11-23289259, 23266861, 23266867; Fax: 011-23243014; Website: www.cbspd.com; E-mail: [email protected]; [email protected].

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Representatives Hyderabad Pune Nagpur Manipal Vijayawada Patna

To My parents Late Haji Nizamsaheb K Kazi Late Hajjan Mrs Jainnabbi N Kazi My wife Kamartaj For tolerating my preoccupation And my daughter Sadiya For understanding me And Students For appreciating my way of teaching and providing me a continuous stimulus to write the book

Foreword to the Second Edition

P

rof SN Kazi’s Exam-Oriented Anatomy, 2nd edition, is going to compete with all other books on the subject available in the market. It is not only simple, digestible and very attractive but also exceptionally informative and rich into the extent that even heavy textbooks do not carry so much information. I have great respect for him, for his dedication and lust for writing book. I wish him all the best. Dr Nafis Ahmad Faruqi Professor Department of Anatomy Jawaharlal Nehru Medical College Aligarh Muslim University, Aligarh, UP India

Foreword to the First Edition

P

rof SN Kazi’s book is intended to help medical students rapidly master complex intricacies of human anatomy that is essential to clinical care. This book was written to fulfill the need for a brief, but readable, summary of the relevant anatomy, with succinct notes on applied anatomy wherever indicated. It addresses the diverse and mounting need of medical students preparing for professional examinations. The text will not only enhance the knowledge to an extent sufficient to satisfy the examiners but will also equip the readers with the necessary understanding of applied anatomy for future practice. A recurring problem in medical education is the common inability of the students to relate the large body of factual knowledge to practical application in their future clinical training. A commendable endeavour has been made by Prof Kazi to bridge the gap between rote anatomy and clinical relevance. The mnemonics and humour in this book do not intend any disrespect for anyone, rather they are employed as an educational device, as it is well known that the best memory techniques involve the use of ridiculous association. Stephen Goldberg in his unique book titled “Clinical Neuroanatomy Made Ridiculous Simple” has already demonstrated their efficacy superbly. Books

LAQs

SAQs

SNs

Keywords Line diagrams Tables

Above diaphragm

93

20

156

91

254

47

Below diaphragm

47

38

125

49

254

47

This book is not designed to replace standard reference textbooks, but rather is to be read as a companion text before appearing in an examination. This will enable the student to gain an overall perspective of essential anatomy. My best wishes for the success of this endeavour which merits appreciation. Prof (Dr) Mahdi Hasan MBBS, MS (Hons.), FICS, FAMS, PhD,DSc, FNA

Professor Emeritus INSA Senior Scientist, Department of Anatomy Chhatrapati Shahuji Maharaj Medical University (King George’s Medical University) Lucknow, UP (India) Formerly Professor and Chairman, Department of Anatomy and Founder Director Interdisciplinary Brain Research Center Dean, Principal and Chief Medical Superintendent Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, UP (India)

Foreword to the First Edition

A

ll the medical colleges in the state of Maharashtra were affiliated to eight different conventional universities in the state up to 1997. After the establishment of Maharashtra University of Health Sciences in the state in 1998, all of them were affiliated to this single state level university. Previously syllabi and pattern of examination were different but the new pattern (1 + 1½ + 2 years) of curriculum recommended by the Medical Council of India while the conventional universities were following the old (1½ + 1½ + 1½ years) pattern. First time in the examination, LAQ, SAQ and MCQ patterns were introduced by MUHS. On the background of the reduced duration for both students (for learning) and teachers (for teaching) of I MBBS, there was a need for examinationoriented revision book. It is really a great pleasure for me to introduce this book on human anatomy written by one of my ex-colleagues, Dr SN Kazi. I have gone through the manuscript of this book which adequately covers the subject. Usually students have to purchase separate books for anatomy, histology, embryology, general anatomy, genetics, etc. Dr. Kazi has tried to cover all these branches in simple language with the help of computerized line diagrams. It is designed to meet the need of the undergraduate exam going students. Most of the information are given in tabular forms, easy to compare and remember and clinical applications of the subject have been touched adequately. The book speaks the long experience of the author in the subject and will minimize the stress and strain of a medical student during pre-examination period. I congratulate the author for this venture and wish the book great success.

Shingare PH Professor and Head, MS Department of Anatomy Grant Medical College and Sir J J Group of Hospitals Byculla, Mumbai Director of Medical Education and Research, Maharashtra Ex-Dean, Faculty of Medicine, North Maharashtra University Ex-Controller of Exam, MUHS, Nashik Ex-Chairman, BoS Preclinical, MUHS, Nashik Member of BoS Preclinical Faculty of Medicine and Faculty of Dentistry, MUHS Ex-Vice Dean UG, Grant Medical College, Mumbai Ex-Vice Dean PG, Grant Medical College, Mumbai

Preface to the Second Edition

I

am very much excited to present the 2nd edition. Initially I thought it will not take much time, but as I started preparing for the 2nd edition, new ideas start clouding in my mind and the ideas went on increasing. In the last 15 years, I received many feedbacks about inadequate answers, too much simplicity of the text, too many mnemonics. I reviewed various books on memory techniques and came with various ideas. I am happy to share the experiences of teaching in different parts of country. In north and central part of India, the main barrier is writing skills. The students are either from Hindi medium or language of regional medium. The immediate challenges after joining medical course is communication and managing vast syllabus. I have made an attempt to write in very simple language. In the first reading only, the student should be able to understand the contents. I have used the symbols for most of the words. It is rightly said “A picture is equal to thousands of sentences. A cartoon is worth of thousands of pictures”. Visual memory works better for the pictures than the texts. Colours have deep impact than black and white. Kinesthetics have far more effect as compared to auditory and visual. Combined effects of auditory, visual and kinesthetic have profound effect on memory. A sincere attempt is made not only to give the contents of the subject, but also to make the student remember the subject by using various techniques. The author has attended the lectures of the many anatomists, studied the delivery of lectures. He has picked up the concepts and presented in the form of book. The book is collections of techniques used by well-known anatomists of India.

Memory Technique 1. Association memory A. Day-to-day examples: City bus for ascending and descending tracts. B. Association of letters a. After “C” to recollect the nuclei of cerebellum. b. ABCD for the normal constrictions of oesophagus c. Ruffini for red and Krause for cold receptor. This was contributed by Dr Nandedkar madam, a senior anatomist from AFMC. C. Association of digit 10 for 4 important information of oesophagus. a. Length of oesophagus b. Constrictions of oesophagus c. Opening in diaphragm at 10th thoracic vertebra d. First mark on the paediatric Ryles tube. 2. Use of one’s hand for representation of various structures and relations A. Branches of splenic artery B. Intermuscular spaces C. Use of 3 fingers for transpyloric plane at lower 1st lumbar D. Branches of basilar artery E. Tributaries of coronary sinus 3. Framing the rules for registration of information A. Rule of alternate framed by honorable late Padmashree Dr Mahdi Hasan to a. Recollect the

viii

Exam-Oriented Anatomy

I. Paired and unpaired branches of abdominal aorta II. Peritoneal and retroperitoneal structures. b. Dropping the alternate letters to recollect the names of extrapyramidal tracts. B. Use of jiggle “Carotico parotico Tonsilii Tympani” to complete the distribution of glossopharyngeal nerve. This is contributed by famous anatomist and surgeon Dr Kadasne, author of many textbooks. C. Use of fingers to differentiate to walls of artery and vein. This is contributed by Dr Krishna Garg madam, editor of world famous textbook BD Chaurasia’s Human Anatomy. 4. Link technique 5. Meaning of words A. Dura—hard, durable B. Dia—in between

6. Peg technique Mnemonic—Laila Loves Majnu for the branches of lateral cord of brachial plexus. 7. Simile: Course of hepatic artery represented by badly driven nail. Referred from Surgical Synopsis. 8. Picture mnemonic to represent Cri du chat syndrome. 9. Stories A. A girl from South and boy from Chandigarh had friendship in Jaipur. They got married in Jaipur but marriage could not survive because of different culture and food habit. They got divorced. Boy went back to Chandigarh and got married in own community. This story is appealing for origin, course and distribution of accessory nerve. The story was fabricated by Dr Aruna Mukherjee, a well-known anatomist. B. A story of water pipe for the course of internal pudendal artery. 10. Text in simple English. 11. Things added with religious sentiments: Dr Mysorekaraneminent, Professor of AFMC, used to teach functions of thalamus by giving simile of thalamus to God Nandi and cerebrum with Lord Mahadev. 12. The concept of mind mapping, introduced by Tony Buzan, is used to depict the branches of brachial plexus. 13. Use of celebrities A. Mary Kom—action of serratus anterior B. Ajay Devgn for overriding of horse to make understand the features of Fallot’s tetralogy. 14. Use of key advertisements as the keywords—PRO V for features of Fallot’s tetralogy. 15. Use of airplane and navies for reminding suprascapular artery and nerve, above and below the suprascapular ligament. 16. Use of pictures of anatomy students whose passion is body building. A photo of Wasim Khan is used to display the actions of sternal and clavicular head of pectoralis major. 17. Fruit of pine tree to show pineal body. 18. Use of symbols and pictures of muscles to boost the memory. It was a feedback from the passed-out students that there is mismatch between what is taught in applied anatomy in the first year and what is expected in clinical posting. To fill up the gap, the author has reviewed the applied anatomy from physician, general surgeon, ENT surgeon, ophthalmologist, orthopaedic surgeon, and geneticist. The author has reviewed various regions from senior anatomists. All the feedback has been meticulously rectified. Separate boxes are introduced for the understanding of the subject and for memorization. Shoukat N Kazi

Acknowledgements to the Second Edition

I

recollect the days, when I determined to write for the second edition. I thought of getting all the books of anatomy that are freely available and accessible. I collected books from all the old book bazar in Delhi, Mumbai, Pune, Pimpri, Lucknow, Ahmedabad, Rajkot. I am very much thankful to Dr TC Singel, Professor, Department of Anatomy, Zydus Medical College, who took me to various old bookstores in Ahmedabad and made them available. He also lent me the library books. It was a great help. I could get the books which are not available in any of the college library. I am very much grateful to him. I cannot afford to forget the continuous encouragement given by Mr Bhagwan Yadav, Chairman, Managing Director, Prasad Institute of Medical Sciences, Lucknow. Scanning of the book was done by our office staff, namely Prajakta, Rhutuja. I am thankful to them. I need to mention the name of Mr Rehan Ansari, (HR, Prasad Institute of Medical Sciences, Lucknow) who got the books scanned in a very short time. There were vital technical issues, because of which I was handicapped. The problems were resolved by my nephew, Mr Wahab Kabir Kazi. I am very much thankful to him. The basic suggestions of diagrams were made by a corel artist Mr Sanjay, CBS Publishers & Distributors. I am thankful to him. I am really lucky to have the contributions from many professors. To start with, Mrs Jasmine Naik drew some of the diagrams in corel draw but because of her child’s health she could not continue. The work was continued by Mrs Zeenat Shaikh. She really put her heart in diagrams. She learnt all the intricacies of anatomy subject and gave her 100% to make the diagrams right. She is very much concerned for the success of the book. The repeated editing of the text and layout of diagrams, sequencing of questions, was done untiringly by Miss Parveen Shaikh and Mrs Jyoti Dhage. In addition to editing, Miss Parveen Shaikh has kept an eye on all the activities and coordinated in a very efficient way. They are the backbones of the book, without their help, the quality of the book was not possible. I am really blessed to have the staff, namely Miss Parveen Shaikh, Mrs. Jyoti Dhage and Mrs Zeenat Shaikh. Mrs Maya Bhujbal, and Mr Uday Jadiye, who have helped in minute layout of the book. I am indebted for the help my brother Mr Kabir Kazi has extended to me. He has helped me in organizing guest lectures, workshops and made me tension free to write the book. It was a continuous support to me. The continuous inspiration and motivation was given by my brothers Mr Shikandar, Allabaksh and Najir Kazi. The technical support was given by Mr YN Arjuna Senior Vice-President—Publishing, Editorial and Publicity, and his team. He has understood me and helped without any hesitation.

x

Exam-Oriented Anatomy

The real financial help was extended by Mr Satish Kumar Jain, CMD , CBS Publishers & Distributors. His help was stress bursting to me. The quality of the book has reached only because of his timely help, and the patience he has shown to me. We have very good bonding for so many years. I am really thankful from the bottom of my heart to Mr Varun Jain, Director, who is dynamic in implementing various technology in the books. The animation of neuroanatomy and upper limb and abdomen is being introduced, only because of his initiation. I owe him a lot. The real tolerance and patience were given by my better half Mrs Kamartaj and my daughter Miss Sadiya. I did not give any time and attention to family activities. I appreciate their understanding.

Special Thanks I am extending my sincere and special thanks to the following persons, without whom the book would not have been completed. • Dr PH Shingare, Professor and Head, Department of Anatomy, Grant Medical College, Mumbai, has meticulously corrected the text and has given solutions to diagrams. He has tolerated my disturbance at odd hours in his busy schedule. • Dr (Mrs) Kanaklata Iyer, Professor of Anatomy at Somaiya Medical College, Sion, Mumbai, has really given a breakthrough to the problems of diagrams. She has helped out rightly by sparing her valuable time through her busy schedule by taking keen interest. She has contributed diagrams of gross anatomy of abdomen, inferior extremity and general embryology. • Dr Savgaonkar, Professor of Anatomy at BJ Medical College, Pune, has drawn histology diagrams of abdomen section. He being my close friend, understood the difficulties and offered his help by completing the diagrams in very short time. • Dr Anjali Dhamangaonkar, Associate Professor, in Anatomy at GS Medical College, Mumbai, has contributed to the general embryology diagrams. It was very difficult for her to give some time. But her desire to help me has solved the problems. • Dr Manvikar Purushottam Rao, Lecturer in Anatomy at Dr DY Patil Medical College, Pimpri, has drawn some of the diagrams of general histology. He is the main push for animation work. • Dr Kadasne DK, the author of Kadasne’s Textbook of Anatomy (Clinically-oriented), has allowed me to use some of the diagrams from his book. • Dr Umarji, Professor and Head, Department of Anatomy, Krishna Institute of Medical Sciences, Karad, has drawn a few diagrams of general anatomy.

Shoukat N Kazi

Contributors Arudyuti Chowdhury MS, DGO Associate Professor, SRM Medical College, He was my roommate at SRM Medical College, Chennai. Dr Arudyuti Chowdhury is constant motivators. He has helped me in all the activities. His word of suggestion is important for me.

Ashok Kumar Rawat

MS (Ortho)

Assistant Professor, Department of Orthopedics, Associate Professor, Prasad Institute of Medical Sciences, Lucknow. He has helped in giving fine touch of applied aspects of joint.

Gangane Professor and Head, Department of Anatomy, Medical College, Navi Mumbai. Thank you very much for finding time for approving the contents.

Jyoti Kulkarni Professor in Anatomy in Nepal She has gone meticulously in all the texts and diagrams of books and given valuable suggestions. The quality of the book is definitely improved because of her suggestions. I am very much obliged and thankful for her help.

He is courageously fighting his health issue like a warrior. I know him since last 15 years. He is very much energetic. The energy and enthusiasm have increased many folds after he met his health issue. I think adverse situations boost his energy. I do not know from where he gets energy to do such activities. I pray God to give him long healthy life.

Nayana Karodpati Professor (ENT, DYPMC), Pimpri, Pune

She edited the text and added the topics which are of clinical importance. Hearty thanks for the help.

P Vatsalaswamy MD Director of DYPMC, Pimpri, Pune In spite of her busy administrative activities and family commitments, she could spare time and could help me. I am very much obliged. She has reviewed superior extremity. She has gone in details of each word of text and given the feedback. Salamat Khan Professor of Surgery, Prasad Institute of Medical Sciences, Lucknow. Dr Salamat Khan has voluntarily helped me in reviewing applied anatomy of limbs, abdomen, head, neck, face, thorax, and brain. He has gone word to word and gave the suggestions. I salute him for his help.

Manvikar Professor and Head, Department of Anatomy, Padmashree, Dr DY Patil Medical College, Pimpri, Pune. Thanks very much for giving genetic inputs.

Sunita Nayak Assistant Professor All India Institute of Medical Sciences, Patna

MC Srivastav Medical Superintendent and Associate Professor of Medicine, Prasad Institute of Medical Sciences, Lucknow. He is kind enough to add EKG changes in blockage of coronary arteries.

Murugan Kutty Gopalan

Ubaidur Rehman Medical Superintendent, Prasad Institute of Medical Sciences, Lucknow. He has helped in updating ophthalmology chapters. I was lucky to be associate with him.

BSc, MBBS, DMA (USA)

Head, Departments of Medical Illustrations, Digital Health, Clinical Skills Simulation Center and Telemedicine, Amrita Institute of Medical Sciences and Research Center, Kerala, India. He is involved in the Simulation-Based Medical Education in giving training in various clinical skills. He is intensely working on introducing new generation Medical Haptics, Robotic Surgery, Cardiac-Neuro-Ortho interventional Simulaids for the super-specialty branches in Medicine and Surgery. He has won several regional, national and international awards for his innovative illustrative works. All histology diagrams of 2nd edition are fabricated by Dr Gopalan. Apart from contributions to the book, he is my very close friend, whose door I can knock for any help any moment. I am heavenly blessed to have a friend like Dr Gopalan.

Vaishali Bharambe MD, PhD Ex-professor, DY Patil Medical College, Pimpri, Pune Presently she is working as a Professor and Head, Symbiosis Medical College, Pune. She was very much busy in preparation of PhD. In spite of her hectic schedule, she could review the diagrams of lower limb. I owe her. Vinod Kathju Former additional Principal, Dr SN Medical College, Jodhpur I am very much thankful for his kind guidance and contribution

Abdomen: Animation Sr. No.

Duration

Question

Topic

AA1

9.56

LAQ-12

Introduction of abdominal aorta

AA2

3.45

SN-42

Inferior phrenic artery

AA3

3.59

SN-35, LAQ-9

Coeliac trunk

AA5

5.24

SN-33

Splenic artery

AA10

3.12

SN-50

Middle suprarenal artery

AA28

4.00

LAQ-12

Cartoon of abdominal aorta

AA29

4.00

OLA-18, SN-41, LAQ-12, SAQ-7

Technique to find vertebral level of branches of abdominal aorta

AA30

4.09

SAQ-7, SAQ-8

Technique to find level of suprarenal, renal, lumbar and median sacral artery

AA31

4.40

LAQ-24

Simile of internal pudendal artery

Contents Foreword to the Second Edition by Dr Nafis Ahmad Faruqi Foreword to the First Edition by Prof (Dr) Mahdi Hasan Foreword to the First Edition by Shingare PH Preface to the Second Edition

iv v vi vii

Section 1 General Embryology 1. Cell Division SN-1 SN-2

3

Mitosis 3 Meiosis 5

2. Spermatogenesis SN-3 SAQ-1 SAQ-2 SN-4 SN-5

Spermatogenesis 10 Spermiogenesis 12 Sperm 12 Capacitation of sperm Oogenesis 13

10

13

3. The Menstrual Cycle SN-6

15 17

Umbilical cord 28 Intra-embryonic mesoderm (secondary mesoderm) 29 Allantois 31 Septum transversum 32

6. The Placenta SN-18 SN-19 SN-20 SN-21 SN-22 SN-23 SAQ-4 SN-24 SN-25

Fertilization 17 Amnion 19 Yolk sac 20 Primitive streak 22 Somites 24 Trophoblast 25

26

Notochord 26 Connecting stalk 27

SN-26 SAQ-5

46

Coelomic wall epithelium 46 Surface ectoderm epithelium 47

8. Nervous System SN-27

33

Implantation 33 Blastocyst 35 Decidua 35 Placenta 37 Types of placenta depending upon shape 39 Types of placenta depending upon attachments 40 Placenta praevia 41 Chorion 43 The maternal–foetal barrier 44

7. Urogenital System

5. Embryonic Disc SN-13 SN-14

SN-17 SAQ-3

Graafian follicle 15

4. Formation of Germ Layers SN-7 SN-8 SN-9 SN-10 SN-11 SN-12

SN-15 SN-16

49

Neural crest 49

Section 2 Genetics 9. Chromosomes and their Aberrations 53 SN-1 SN-2 SN-3 SN-4 SN-5 SN-6 SN-7 SN-8

Gene 53 Barr body (sex chromatin) 54 Structure of chromosome 55 Classification of chromosomes 57 Chromosomal aberrations 57 Chromosome banding 59 Trisomy 21 60 Turner syndrome (45 X) 62

SN-9 SN-10 SN-11 SN-12 SN-13 SN-14

Klinefelter syndrome (47 XXY) 63 Cri du chat syndrome (5p-) 65 Nondisjunction 67 Aneuploidy 68 Spectral karyotyping (Sky) 68 What are genetic disorders? 69

10. Mendelian Genetics SN-15 SN-16 SN-17

Autosomal dominant inheritance 71 Autosomal recessive inheritance 72 X-linked recessive traits 73

71

xiv

Exam-Oriented Anatomy

Section 3 Abdomen 11. Introduction and Osteology SN-1 SAQ-1

OLA-3 LAQ-2 OLA-4 OLA-5 SAQ-3 SAQ-4 SAQ-5 SN-5 SN-6 OLA-6 SN-7 SN-8 SN-9

80

LAQ-4 SN-23 SN-24

Transpyloric plane (Addison’s plane) 80 Sites of portocaval anastomoses 82 Caput medusae 83 Inguinal ligament 84 Rectus abdominis 85 Rectus sheath 85 Name the contents of inguinal canal in male 88 Name the contents of inguinal canal in female 88 Inguinal canal 89 Lacunar ligament 93 Attachments to pubic tubercle 94 Superficial inguinal ring 94 Deep inguinal ring 95 Coverings of spermatic cord 95 Spermatic cord 96 Hesselbach’s triangle (trigonum inguinale—inguinal trigone) 97 What is inguinal hernia? 98 Inguinal hernia 98 External oblique muscle of anterior abdominal wall 99 Transversus abdominis muscle 100

13. Male External Genital Organs SN-10 SN-11 SN-12 SN-13 SN-14 SAQ-6 SN-15 LAQ-3

OLA-8

Spina bifida 77 Sacral hiatus 78

12. Anterior Abdominal Wall SN-2 OLA-1 SAQ-2 SN-3 SN-4 LAQ-1 OLA-2

77

102

Histology of testis 102 Descent of testis 103 Thermoregulation of testis 105 Blood supply of testis 105 Development of testis 106 Epididymis 108 Layers of scrotum 108 Testis 109

14. Abdominal Cavity and Peritoneum 113 SN-16 SN-17 SN-18 SN-19 SN-20

Peritoneal reflection 113 Foramen of Winslow (auditus to lesser sac, epiploic foramen) 113 Lesser sac (omental bursa) 114 Morison’s pouch 117 Douglas’ pouch/pouch of Douglas (rectouterine pouch) 118

15. Abdominal Part of Oesophagus and Stomach 120 SN-21 OLA-7 SN-22

Blood supply of stomach 120 Bare areas of stomach 121 What is the surface mucus cells and how do they differ from neck mucus cells in stomach? 122

Differentiate between fundus and pylorus of stomach histologically 123 Stomach 123 Stomach bed 131 Oesophageal varices 132

16. Small and Large Intestines SN-25 SN-26 SN-27 SN-28 OLA-9 LAQ-5 SN-29 SN-30 SN-31 SN-32 OLA-10 LAQ-6 OLA-11 LAQ-7

134

Relations of 1st part of duodenum 134 Relations of 2nd part of duodenum 135 Relations of 3rd part of duodenum 136 Relations of 4th part of duodenum 137 Peritoneal recesses around duodenum 137 2nd part of duodenum 138 Duodenal cap 143 Ligaments of Treitz (suspensory muscle of duodenum) 143 Meckel’s diverticulum 144 Differences between jejunum and ileum 145 Peritoneal recesses around caecum 146 Caecum 146 McBurney’s point 149 Appendix 149

17. Large Blood Vessels of the Gut 155 OLA-12 SN-33 LAQ-8 SN-34 OLA-13 SN-35 LAQ-9 SN-36 OLA-14 SN-37 LAQ-10 SN-38 LAQ-11 OLA-15 SN-39 OLA-16 OLA-17 SN-40 OLA-18 SN-41 SN-42 LAQ-12 SAQ-7

Branches of splenic artery 155 Splenic artery 155 Inferior mesenteric artery 157 Obturator artery 160 Enumerate the branches of coeliac trunk 162 Enumerate the branches of coeliac trunk 162 Coeliac trunk (coeliac axis, coeliac artery) 163 Left gastric artery 166 Branches of superior mesenteric artery 168 Enumerate the branches and distribution of superior mesenteric artery 169 Superior mesenteric artery 169 Marginal artery 173 Portal vein 174 Enumerate the branches of hepatic artery (hepatic artery proper) 179 Hepatic artery proper 179 Calot’s tringle 180 Branches of common hepatic artery 181 The common hepatic artery 181 Enumerate the branches of abdominal aorta 183 Abdominal aorta 184 Inferior phrenic arteries 186 Abdominal aorta 188 What is the vertebral level of suprarenal, renal, lumbar and median sacral arteries 193

xv

Contents SN-43 SAQ-8

Median sacral artery 196 What are the unpaired and ventral branches of abdominal aorta? 198

18. Extrahepatic Biliary Apparatus 199 LAQ-13

Extrahepatic biliary apparatus 199

19. Spleen, Pancreas and Liver OLA-19 SN-44 LAQ-14 SN-45 OLA-20 OLA-21 SN-46 SN-47 LAQ-15 LAQ-16

20. Kidney and Ureter OLA-22 OLA-23 SN-48 SN-49 OLA-24 OLA-25 OLA-26 SAQ-9 LAQ-17 LAQ-18

205

Enumerate the functions of spleen. Give two causes of its enlargement 205 Blood circulation in spleen 205 Spleen 206 Relations of liver 211 Portal lobule 212 Acinus of liver 213 Bare areas of liver 213 Lobes of liver 214 Liver 215 Head of pancreas 220

227

Name the nerves related to the posterior surface of kidney 227 Give the relations of posterior surface of left kidney 227 Vascular segments of kidney 227 Psoas major 228 Renal angle 229 Floating kidney 229 Pelvic kidney 230 Renal fascia 230 Kidney 231 Ureter 238

21. Suprarenal Gland and Chromaffin System 248 OLA-27 OLA-28 OLA-29 OLA-30 LAQ-19

State the two developmental components of adrenal gland? 248 What is the structure of adrenal medulla and what are its secretions? 248 What is chromaffin reaction? 248 Name the hormones secreted by suprarenal gland 249 Suprarenal gland 249

22. Diaphragm OLA-31 OLA-32 LAQ-20 OLA-33

23. Posterior Abdominal Wall LAQ-21 SN-50 SN-51 SN-52

256

Structures passing through the aortic opening of the diaphragm. 256 Referred pain 256 Diaphragm 257 Diaphragmatic hernia 262

Renal artery 263 Middle suprarenal artery 266 Testicular artery 267 Ovarian artery 270

263

SN-53 SN–54 OLA-34 SN-55 SN-56 SN-57 SN-58 OLA-35 LAQ-22 OLA-36 SN-59

Lumbar arteries 272 Common iliac arteries 274 External iliac artery 276 Relations of external iliac artery 276 Branches of external iliac arteries 278 Superior vesical artery 280 Lateral sacral artery 281 Tributaries of inferior vena cava 282 Inferior vena cava 283 Cisterna chyli 287 Cisterna chyli 287

24. Perineum

289

OLA-37

Enumerate the structures piercing the perineal membrane in male 289

SN-60

Perineal body (central perineal tendon) 289 Attachments and nerve supply of external anal sphincter 291 External anal sphincter 291 Boundaries of ischiorectal fossa 294 Contents of ischiorectal fossa 295 Ischiorectal fossa 295 Pudendal canal (fascial canal, Alcock’s canal) 297 Internal pudendal artery 298 Structures piercing perineal membrane in

OLA-38 SN-61 OLA-39 OLA-40 LAQ-23 SN-62 LAQ-24 OLA-41

female OLA-42 SN-63 SN-64 LAQ-25 LAQ-26

304

Perineal membrane 304 Urogenital diaphragm 304 Perineal membrane (inferior fascia of urogenital diaphragm) 306 Superficial perineal pouch 308 Deep perineal pouch 312

25. Urinary Bladder and Urethra SN-65

316

OLA-44 LAQ-27

Automatic bladder (neurogenic bladder, reflex bladder) 316 What is the capacity of gallbladder and urinary bladder? 316 Nerve supply of urinary bladder 316 Urinary bladder 317

SN-66

Female

urethra 323

LAQ-28

Male

urethra

OLA-43

26. Female

325

Reproductive Organs 330

OLA-45 SN-67 LAQ-29 SAQ-10 LAQ-30 OLA-46 SN-68 OLA-47

Prolapse of uterus 330 Prolapse of uterus 330 Ovary 331 Ovarian fossa 335 Uterine tube 335 What is hysterosalpingography? 338 Applied importance of supports of uterus 338 Abnormal positions of uterus 339

xvi

Exam-Oriented Anatomy SN-69 LAQ-31 SN-70 SN-71

27. Male OLA-48 LAQ-32 OLA-49

Broad ligament of uterus 339 Uterus 340 Uterine artery 345 Middle rectal artery 348

SN-72 OLA-53 LAQ-33 OLA-54 SN-73

Reproductive Organs 350 Median lobe of prostate 350 Prostate 350 Benign prostatic hypertrophy 356

28. Rectum and Anal Canal

LAQ-34

29. Walls of Pelvis OLA-55 SN-74 SN-75 SN-76 SN-77

357

OLA-50

Prostatic urethra

OLA-51

Urethral sphincters 357

OLA-52

Internal anal sphincter

357 358

Anal sphincters 358 Mucosal folds of rectum 358 Rectum 359 Blood supply of anal canal 364 White and pectinate lines of anal canal 364 Anal canal 364

Index

Attachments to iliac spines Internal iliac artery 370 Inferior vesical artery 373 Inferior gluteal artery 374 Iliolumbar artery 375

370 370

377

1 General Embryology

• Cell Division • Spermatogenesis • The Menstrual Cycle • Formation of Germ Layers • Embryonic Disc • The Placenta • Urogenital System • Nervous System

1 Cell Division

SN-1

Mitosis

(Mitos—thread, schisis—cleavage) It is cell division where threads appear during cleavage of somatic cell. It results in distribution of identical copies of parent cell into two daughter cells. 1. Interphase (Fig. 1.1): Cells do not actively divide but elongate. With onset of mitosis, chromosomes undergo coiling condensation. Chromosome contains two parallel subunits called chromatids connected by centromere. A. Before mitosis: Chromosome number is diploid and DNA is tetraploid. B. After mitosis a. Chromosomes remain diploid, and b. DNA material becomes diploid in amount.

A

B

Fig. 1.1: Interphase: (A) Early interphase: Chromosomes are seen as extended threads; (B) Late interphase: There is duplication of DNA material

2. Phases A. Prophase (pro—before) (Fig. 1.2): It is the 1st stage of cell division. a. Chromosomes are recognized as a structure of chromatids and centromere. b. Chromatids are shortened. 3

4

Exam-Oriented Anatomy

c. Centrioles separate and start migrating to each pole. d. Spindle and asters are formed, together called as diaster. e. Nucleolus and nuclear membrane disappear.

General Embryology

1 A

B

Fig. 1.2: Prophase: (A) Early prophase: Chromosomes seen prominently. Centrioles move from each other; (B) Late prophase: The nuclear membrane disappears and spindle is formed

B. Metaphase (meta—after) (Fig. 1.3): It is the cell division after prophase. a. Chromosomes migrate towards equators. b. Spindle occupies central position. c. Centromeres are attached to microtubules.

Fig. 1.3: Metaphase: Chromosomes are attached to spindle and are arranged on equator

C. Anaphase (ana—apart) (Fig. 1.4): It is the cell division where the chromosomes move apart. a. Cytoplasmic division starts with appearance of cleavage furrow. b. Chromosomes divide and split at centromere (centromere is double structure). c. Such chromosomes start migrating to each end.

Cell Division

5

Fig. 1.4: Anaphase: Centromeres split. There are two pairs of chromosome. Each pair moves to one pole

D. Telophase (telo—end): It is the end phase of cell division (Fig. 1.5). a. Nuclear membrane reappears. b. Nucleoli reappear. c. Chromosomes are grouped at each end with diploid number.

Fig. 1.5: Telophase: Nuclear membranes are formed. Chromosomes become less prominent.

3. Applied anatomy : Radiation causes change in number of chromosomes and form abnormal chromosomes. SN-2

Meiosis

1. Meiosis: It is the cell division occurring only in the germ cells. There is exchange of genetic material. The daughter cells are not identical. It occurs just before the formation of the gamete. The number of chromosomes is reduced to half. 2. Peculiarities A. Pairing of homologous chromosomes occurs only in meiosis and not in mitosis. B. After fertility, diploid number is restored. C. The genetic exchange occurs in homologous chromosomal pairs.

General Embryology

1

6

General Embryology

1

Exam-Oriented Anatomy

a. In interphase, there is a replication of DNA. b. DNA is tetraploid and chromosome is diploid. I. Meiosis I: It is a reduction division. At the end of meiosis I, each cell contains haploid number of chromosomes. II. Meiosis II: The haploid number of chromosomes is maintained. It resembles mitosis but differs in two respects i. There is no DNA replication prior to this. ii. 2nd meiotic division follows meiosis I without interphase. and 3. Site: Meiosis occurs in the germ cells, i.e. spermatogonium in case of male oogonium in case of female . 4. Stages: Meiosis includes 1st and 2nd meiotic divisions. A. 1st meiotic division: It consists of a. Prophase: It is long and complex process. It has various stages. I. Leptotene (leptos—slender, tene—ribbon) (Fig. 1.6): The chromosomes appear as individual threads, the one end of which is attached to nuclear membrane. They appear beaded due to the presence of centromere.

Fig. 1.6: Leptotene

II. Zygotene (Fig. 1.7) i. There is pairing of homologous chromosomes. Point-to-point pairing occurs. ii. Each pair is a bivalent. iii. There is limited pairing in X and Y chromosomes.

Fig. 1.7: Zygotene

III. Pachytene (pachy—thick) (Fig. 1.8) i. Coiling condensation takes place. ii. Centromere and two chromatids become prominent in chromosome. iii. Each bivalent pair consists of four chromatids and forms tetrad. iv. Crossing over: It is an important stage. The two central chromatids (1 belonging to each chromosome bivalent) become coiled over other so that they cross at a number point.

7

Fig. 1.8: Pachytene

IV. Diplotene (diplotene—duplication) (Fig. 1.9): This stage is characterised by longitudinal separation of members of bivalent, without split in the centromere. Crossing over is complete. In female , the growth of the primary oocyte is arrested in diplotene and prolongs up to ovulation.

Fig. 1.9: Diplotene

V. Diakinesis (Fig. 1.10) i. The chiasmata start resolving. ii. The chromosomes further become condensed and get coiled up. iii. They start migrating towards equator. iv. At the end of prophase, nucleoli and nuclear membrane disappear.

Fig. 1.10: Diakinesis

b. Metaphase I (Fig. 1.11) I. It resembles mitotic metaphase. II. Chromosomes are attached by centromere. The spindle is formed. III. Homologous pairs lie parallel to equator with one member on each side of equator.

1 General Embryology

Cell Division

8

General Embryology

1

Exam-Oriented Anatomy

Fig. 1.11: Metaphase

c. Anaphase (Fig. 1.12): The whole chromosome with two chromatids goes to one pole while another chromosome of homologous pair goes to other side. Such migration of bivalent pairs is at random.

Fig. 1.12: Anaphase

d. Telophase (Fig. 1.13): The chromosome in each cell is reduced to haploid number.

Fig. 1.13: Telophase

B. The 2nd meiotic division is followed by a short interphase. It differs from usual interphase in that there is no duplication of DNA. It is similar to mitosis. However, the daughter cells are not identical in genetic content. 5. Significance A. 1st meiotic division provides a. Genetic variability through the process of crossing over. b. Random distribution of homologous chromosomes to daughter cells. B. 2nd meiotic division provides a. Germ cells with haploid number of chromosome, and b. Haploid amount of DNA. c. It is similar to mitosis except chromosomes in daughter cell, which are not alike.

9

Cell Division

6. Applied anatomy

¾ Failure in separation of chromosomes or abnormal in number of chromosomes • Non-disjunction: It is failure of separation of two chromosomes at anaphase. ƒ Trisomy: There are 47 chromosomes, there being three identical instead of one of the normal pairs, e.g. – Mongolism or – Down’s syndrome: Trisomy 21. ƒ Presence of extra X or Y chromosome e.g. – 47, XXX: Abnormal female

.

– 47, XXY: Klinefelter syndrome—abnormal male . – 47, XYY: Abnormal male

.

• Abnormal number of chromosomes: There are only 45 chromosomes. Here one pair is represented by single chromosome. 45, X, e.g. XO Turner’s syndrome. Gamete may have diploid number of chromosomes so that zygote will have 46 + 23 (i.e. 69). • Abnormalities in the shape – Translocation: Part of a chromosome may get attached to a chromosome of a different pair. – Deletion: Part of chromosome may be lost. – Duplication of genes. – Inversion: Chromosome may get inverted before joining the opposite chromosome.

1 General Embryology

¾ Abnormalities of form • Giant (large): Spermatozoa are too large. • Dwarf (small): Spermatozoa are too small. • There may be duplication of head, body or tail. • The ovum may have unusually large nucleus.

2 Spermatogenesis

SN-3

Spermatogenesis

Introduction: It is the complex series of changes by which spermatogonium is transformed into spermatozoa. 1. Site A. It takes place in seminiferous tubules. B. It is controlled by testosterone. C. It begins at puberty and continues up to the old age. 2. Duration: 64 days are required to complete one cycle of spermatogenesis. These complex series of changes do not take place in all parts of seminiferous tubules simultaneously. 3. Stages: The following are the stages (Fig. 2.1). A. Spermatocytosis: It involves series of mitotic divisions from which spermatogonium A is converted to primary spermatocyte. Primary spermatocyte is comparatively larger cell due to increased nuclear and cytoplasmic material. B. Meiosis: Primary spermatocyte (diploid) soon enters into 1st meiotic division, transforms into secondary spermatocyte (haploid). It is changed into spermatid by 2nd meiotic division. Spermatids have haploid number of chromosomes. C. Spermiogenesis: It involves series of changes by which spermatid (non-motile) is converted into an elongated (motile) sperm. 4. End result of spermatogenesis: In one cycle, 4 motile sperms are formed from one primary spermatocyte which possess haploid number of chromosomes. 5. Amount of ejaculation is 2–3 ml. A. Each ml contains nearly 100 million sperms. B. The life of the sperm is 24–48 hours. C. Rate of motility is 1.5 to 3 mm/min. D. Contents of semen are a. Sperm, and 10

Spermatogenesis

11

Fig. 2.1: Stages in spermatogenesis

b. Chemicals and enzymes I. Citric acid, II. Lactic acid, III. Pyruvic acid, IV. Fructose, V. Proteolytic enzymes, VI. Prostaglandins, VII. Inositol, and VIII. Sorbitol. 6. Anomalies (Fig. 2.2): They can be grouped in A. Morphological a. Double heads b. Poorly motile B. Numerical a. Oligospermia: Less than 10 million sperms/ml. b. Azoospermia: Zero sperm count.

Fig. 2.2: Anomalies of spermatozoa

General Embryology

1

12

SAQ-1

Exam-Oriented Anatomy

Spermiogenesis

1. Spermiogenesis: It involves series of changes by which spermatid (non-motile) is converted into an elongated (motile) sperm. The cell organelle transforms into following structure.

General Embryology

1

2. Golgi complex forms acrosomal cap on upper two-thirds of circumference of the head of the sperm. It helps in penetration of the cells present in corona radiata and zona pellucida (secondary oocyte). It contains enzymes, namely A. Acrosin, B. Acid phosphatase, C. Proteases, and D. Hyaluronidase. 3. The nucleus is converted into head of the sperm. The specific number of chromosome is maintained, i.e. haploid number of chromosome. 4. Mitochondria are arranged in helical form around axoneme of the middle piece. It provides energy for motility. 5. There are two centrioles present at neck and tail of the sperm. A. Proximal centriole is present at the neck. B. Distal centriole is present in tail of sperm. It helps in motility. 6. Residual body: The excess of cytoplasm is shed off which is engulfed by cells of Sertoli. SAQ-2

Sperm

Introduction: It is a male gamete, smaller than the female and is about 45–50 μm in length. It is a motile cell.

gamete, i.e. ovum

Parts: It has following parts (Fig. 2.3). 1. Head a. Shape: Ovoid

/pyriform

.

b. Size: 4 μm. 2. Tail: Principal piece a. Neck: It is constricted part distal to head. b. Middle piece: It contains a motor element—axoneme (central doublet with peripheral doublet) which is surrounded by the course fibres in middle piece and principal piece. The mitochondria are absent in principal piece. c. Proximal piece, and d. Terminal piece.

Spermatogenesis

13

Fig. 2.3: Parts of spermatozoon and their derivation

SN-4

Capacitation of sperm

Introduction: It is the final stage of maturation of sperm. 1. Duration: 7 hours. 2. Site: Female

genital tract.

A glycoprotein coat and seminal plasma proteins are removed from the plasma membrane. They are present in the acrosomal region. 3. Result A. No morphological changes in the capacitate sperm. B. There is increase of the activity. 4. The capacitated sperm comes in contact with corona radiata because of following facts. A. There is an interaction between the zona pellucida and head of the sperm. It includes release of acrosin which helps in digestion of zona pellucida. B. Action of tubal mucosal enzyme. SN-5

Oogenesis

Introduction: It is a process involving complex changes by which oogonia are converted into ova (Fig. 2.4), the female gamete . 1. Site: It takes place in ovary and fallopian tubes. 2. Onset of oogenesis: It begins when the child in the womb of mother. 3. End of oogenesis: It ends at menopause. 4. Duration: It takes approximately 12–60 years to complete one cycle of oogenesis. The minimum average duration of an oogenesis cycle is 12 years. The maximum duration of an oogenesis cycle will be 60 years. gonad is ovary. It has an outer part—the cortex, and inner 5. Ovary: The female part—medulla. The cortex contains large cells called oogonia. All oogonia are produced before birth.

General Embryology

1

14

Exam-Oriented Anatomy

General Embryology

1

Fig. 2.4: Stages in oogenesis

The oogonium enlarges and is called primary oocyte. A. Primary oocyte divides by 1st meiotic division (reduction) into two secondary oocytes. One of two secondary oocytes contains 1/2 number of chromosomes and almost all of its cytoplasm. Second of two secondary oocytes contains only 1/2 number of chromosomes and no cytoplasm. It is called 1st polar body. The 1st polar body is, therefore, formed merely to get rid of unwanted chromosomes. B. Secondary oocyte gets arrested into metaphase. It divides into ovum and 2nd polar body by 2nd meiotic division. This occurs only at the time of fertilization. Table 2.1: Number of germ cells at different stages of life Chronological age

Number

• Intrauterine life

• 7 million germ cells

• At birth

• 1 million oogonia

• At puberty

• 40, 000 oocytes

• Throughout life

• 500 oocytes

• At each ovulation

• 1 secondary oocyte

6. Ovulation: Liberation of the secondary oocyte from the ovary is called ovulation.

3 The Menstrual Cycle

SN-6

Graafian follicle

The ovum develops from oogonia present in the cortex of ovary. These oogonia are surrounded by cells that form stroma. These stromal cells form Graafian follicle. The stages in the formation of Graafian follicle are as follows (Fig. 3.1). 1. Follicular cells: Some of the cells of stroma becomes flattened and surround oocyte and ultimately give rise to ovarian follicle and hence they are called follicular cells. 2. Primordial follicle: The flattened follicular cells become columnar. The follicle up to this stage is called primordial follicle. 3. Zona pellucida (zona—belt, pellucida—transparent): It is a transparent belt present between follicular cells and oocyte. Functions of the zona pellucida A. It protects the oocyte. B. It prevents sticking to the endometrium.

Fig. 3.1: Structures in the Graafian follicle 15

16

4.

5.

General Embrology

1

6. 7. 8.

9.

Exam-Oriented Anatomy

C. It prevents entry of micromolecules into oocyte. D. It prevents entry of more than one sperm into oocyte. Membrana granuloma: Follicular cells proliferate and enclose granules. These are called granular cells. They form a structure having many layers of cells. Such structure is called membrana granulosa. Antrum (cavity): The cavity appears within the membrana granulosa. The cavity of the follicle increases rapidly in size. This results into thinness of wall of the follicle. The oocyte now lies eccentrically in the follicle. Cumulus oophoricus (cumulus—accumulation of cells, oophoricus—surrounding ovum): The follicular cells surrounding oocyte are called cumulus oophoricus. Discus proligerus (discus—flat plate, proligerus—producing offspring): The cells attached to the wall of follicle are given the name discus proligerus. Theca interna (theca—cover): The cells surrounding the membrana granulosa become condensed and form theca interna. They secrete oestrogen hormone and the cells are called thecal glands. Theca externa: The fibrous tissue surrounding the follicle get thickened and are called theca externa.

4 Formation of Germ Layers

SN-7

Fertilization

Introduction: It is the fusion of male oocyte) to form the zygote.

and female

pronuclei (sperm and secondary

1. Site: Fertilization occurs in the ampulla of the fallopian tube. 2. Duration: It occurs within 24 hrs of ovulation. 3. Prerequisite (capacitation): It needs to cross three barriers. Barrier of A. The cells of the corona radiata, B. Zona pellucida, and C. Vitelline membrane. 4. Mechanism (Fig. 4.1) A. Cells of corona radiata are disintegrated by the enzyme hyaluronidase. B. Zona pellucida is digested by enzyme acrosin and neuraminidase. C. Many sperms get embedded in zona pellucida but when 1 sperm reaches vitelline membrane. Following changes occur in the structure. a. Calcium wave spreads in secondary oocyte. b. The cortical granules are released. c. Ovum is formed. d. Second meiotic division is completed. e. The cortical granules react with zona pellucida and make it impermeable to other sperms (i.e. acro-reaction is inhibited). D. Only head enters the cytoplasm and gets changed into male pronucleus. There is replication of DNA material. (Chromosome number may be 22X or 22Y.) E. Female

pronucleus is also formed.

F. Nuclear membrane disappears and mixing of chromosomes occur. 17

18

Exam-Oriented Anatomy

G. It results into diploid number of chromosome. H. The zygote is formed. I. The cleavage starts.

General Embryology

1

5. Results of fertilization A. The oogenesis cycle is complete. B. The chromosomal number is restored. C. The sex is determined. D. The cleavage starts. E. The genetic combination leads to variations in human species.

Fig. 4.1: Fertilization

6. Effects on A. Ovary: The corpus luteum changes to corpus luteum of pregnancy. B. Uterus: The secretory changes start in the endometrium. C. Zygote: The cleavage starts. 7. In vitro fertilization: The pre-ovulatory oocyte is taken out with laparoscopy and is fertilized outside.

Formation of Germ Layers

Amnion

(Amnion—bowl) Introduction: It is thin but tough extra-embryonic membrane derived from amniogenic cells. It forms the wall of the amniotic cavity. It excludes the cells of the ectoderm. It forms the hydrostatic bag. It contains fluid which envelopes the embryo, umbilical cord and fetal part of placenta (Fig. 4.2). 1. Chronological age: 2nd week after fertilization. 2. Responsible cells are amniogenic cells. They are derived from the trophoblast cells which are present on the roof of ectoderm cells. 3. Sources of amniotic fluid are mainly from A. Maternal blood, B. Amniotic cell, and C. Urine secreted by fetus. Table 4.1: Volume of amniotic fluid Weeks

Amount of fluid in ml

• 10

• 30

• 20

• 350

• 37

• 800 to 1000

Fig. 4.2: Formation of extra-embryonic mesoderm and extra-embryonic coelom and structures forming amnion and chorion

4. Circulation of amniotic fluid A. Part of fluid goes into maternal blood. B. Part of it is swallowed by fetus. C. Excess of water in fetal blood is excreted by urine and to the amniotic cavity.

1 General Embryology

SN-8

19

20

General Embryology

1

Exam-Oriented Anatomy

5. Composition of amniotic fluid A. Desquamated fetal epithelial cells, B. Water, C. Fats, D. Enzymes, E. Pigments, and F. Hormones. 6. Significance of fluid A. Allows free movement of fetus which helps in the development of musculoskeletal system. B. Permits symmetrical external growth of the embryo. C. Prevents adherence of amnion to the embryo. D. Protects embryo against injuries. E. Regulates the body temperature of the embryo. F. Dilates cervix during the act of parturition along with chorionic membrane. 7. Anomalies A. Oligohydramnios: The amniotic fluid is less than 400 ml. The complications of the oligohydramnios include fetal abnormalities. These are a. Pulmonary hypoplasia, b. Facial defects, c. Limb defects, d. Urinary agenesis, and e. Compression of the umbilical cord. B. Polyhydramnios: The amniotic fluid is more than 2000 ml. It is associated with the a. Severe anomalies of central nervous system, and b. Oesophageal atresia. 8. Applied anatomy ¾ Amniocentesis: It is a process by which amniotic fluid is removed and studied for the cells by 16 to 20 weeks. ¾ Detection of abnormal fetus, e.g. spina bifida. It is detected by the estimation of alpha-fetoprotein. The level is increased in neural tube defect like spina bifida. ¾ Determination of the sex. SN-9

Yolk sac

Introduction: The inner wall of the cavity of blastocyst is lined by flattened cells called Heuser’s membrane (future endodermal cells). Such structure is called primary yolk sac (Fig. 4.3). It is described in three stages.

Formation of Germ Layers

21

1. Primary yolk sac: During the 9th day of development, flattened cells originating from endoderm form a thin membrane. This is called Heuser’s membrane. This membrane together with the cells of endoderm forms the primary yolk sac.

General Embryology

1

Fig. 4.3: Formation of different yolk sac

2. Definitive or secondary yolk sac: By 13th day, the extra-embryonic mesoderm is filled by the cavity called extra-embryonic coelom. This is much smaller than the primary yolk sac cavity. The decrease in the size is accompanied by the change in nature of lining cells. They are no longer flattened cells. They become cubical.

22

Exam-Oriented Anatomy

3. Tertiary yolk sac: It is remnant of secondary yolk sac. It is divided into following parts. A. Intra-embryonic part: It gives rise to foregut, midgut and hindgut. B. Intermediate or connecting part: It is also called vitellointestinal duct. C. Extra-embryonic part: This is called tertiary yolk sac.

General Embryology

1

4. Chronological age: 2nd week after fertilization. 5. Functions A. Nutrition to the embryo. B. Haemopoiesis C. Formation of a. Epithelium of I. Gastrointestinal tract, II. Respiratory tract, and III. Urinary bladder. b. Male

and female

primordial germ cell.

6. Fate A. The yolk sac detaches from the midgut loop. Its stalk (vitellointestinal duct) remains in continuation with midgut loop. It persists as a diverticulum called Meckel’s diverticulum. B. Allantois in its distal part forms a remnant called urachus. It extends from apex of bladder to umbilicus. With folding of embryo: a. The yolk sac incorporates into the developing gut tube and it reduces considerably. b. It lies in connecting stalk. SN-10

Primitive streak

Introduction: It is a thickened band of ectodermal cells at the caudal end of embryo. It is in the midline. 1. Cells involved: The pluripotent cells, i.e. ability to transform into any type of the cells. 2. Chronological age: 15th day of intrauterine life. It is very important stage in the formation of embryo. It is recollected by associating with the 15th August, the Independence Day of India. 3. Description (Fig. 4.4) A. It continues laterally up to the margins of the embryonic disc. B. It continues caudally up to the cloacal membrane and goes into connecting stalk. C. The cells of primitive streak are absent at a. Prochordal plate, and b. Cloacal membrane. D. The cells passing beyond the prochordal plate form cardiogenic area.

Formation of Germ Layers

23

General Embryology

1

Fig. 4.4: Formation of the primitive streak

4. Functions A. It organizes intra-embryonic mesoderm (i.e. 3rd germ layer). B. It confirms the future craniocaudal axis of the embryo. C. It divides into left and right half of the embryo. D. It differentiates into notochord. 5. Fate: Cells of primitive streak are continuously formed up to 3rd week. They regress but remain up to 4th week. Cells of primitive streak give rise to A. Lateral part of paraxial mesoderm, B. Primordial germ cells, C. Intra-embryonic mesoderm, and D. Extra-embryonic mesoderm. 6. Applied anatomy : If the cells of the primitive streak persis teven after 4th week, they give rise to teratogenic tumour at sacrococcygeal region.

24

Exam-Oriented Anatomy

7. Recent view: Primitive node gives rise to A. Notochord, B. Medial part of paraxial mesoderm, and C. Endoderm. SN-11

General Embryology

1

Somites

Introduction: The solid brick-like segmentation of paraxial intra-embryonic mesoderm on either side of notochord is called somites. 1. Extent: It extends from cranial end of notochord to the coccygeal end. 2. Chronological age: 20 to 30 days. 3. Total number of somites: 42–44. They are as follows Number of somites

Region

•4

• Occipital

•8

• Cervical

• 12

• Thoracic

•5

• Lumbar

•5

• Sacral

• 8–10

• Coccygeal

4. Derivatives (Fig. 4.5) A. Sclerotome a. Axial skeleton, b. Ribs, and c. Sternum. B. Myotome: Muscles of a. Back, b. Front, and c. Limbs. C. Dermatome: Dermis of skin of the a. Back, and b. Front.

Fig. 4.5: Derivatives of somites

5. Nerve supply : Mesodermal somites are supplied by corresponding segments of the spinal cord. 6. Applied anatomy ¾ The age of the fetus can be determined by counting the number of somites. ¾ Spina bifida: The two halves of the neural arch may fail to fuse in the midline. ¾ Hemivertebrae: Incomplete development of one-half of a vertebra.

Formation of Germ Layers

Trophoblast

Introduction: The cells lining the surface of the morula constitute the trophoblast. The trophoblast has a property of attaching itself to and invading any tissue it comes in contact with. Once the zona pellucida disappears, the cells of the trophoblast stick to the uterine endometrium. This is called implantation. Villi are formed as offshoots from the surface of the trophoblast. The trophoblast along with the underlying extra-embryonic mesoderm forms the chorion. The villi arising from chorion is called chorionic villi (Fig. 4.6). Initially, the trophoblast is made up of a single layer of cells. As these cells multiply, two distinct layers are formed. The cells, close to the decidua (most superficial cells), lose their cell walls. Thus, a continuous sheet of cytoplasm containing many nuclei is formed. Such a tissue is called a syncytium. Hence, the layer of trophoblast is called syncytiotrophoblast or plasmodiotrophoblast.

Fig. 4.6: Stages in the formation of chorionic villi

Deep to the syncytium, the cells of the trophoblast retain their cell walls and form the 2nd layer called cytotrophoblast [Langhans layer].

1 General Embryology

SN-12

25

5 Embryonic Disc

SN-13

Notochord

(Noto—relationship to back, chord—rod

shaped structure)

Introduction: It is a solid rod of cells which supports the embryo. 1. Extent: It extends from primitive node to prochordal plate. 2. Situation: Midline of the embryo. 3. Source: Cells of primitive node.

Fig. 5.1: Diagram showing the development of notochord

4. Formation (Fig. 5.1) A. The cranial end of primitive streak (streak—faint, white trace) becomes thick. This thickened part of primitive streak is called primitive node (knot or Hensen’s node). B. A depression appears in the centre of primitive knot—called blastopore. C. Notochordal process: The cells of primitive node present in the central axis migrate cranially towards prochordal plate. D. Notochordal canal: The canal that arises from blastopore and extends into notochord is called notochordal canal. E. Neuroenteric canal: The cells at floor of notochordal canal break and form a communication between amnion and yolk sac through the canal. F. Notochordal plate: The cells in the floor of neuroenteric canal reappear. They fill a gap at the floor and form a plate. Such a plate is called notochordal plate. 26

Embryonic Disc

27

G. Solid notochord: The proliferation of cells of notochordal plate gives rise to solid notochord, which extends from prochordal plate to primitive node. 5. Functions A. It supports the embryo. B. It acts as a vertebral column in the embryonic life. C. It induces surface ectoderm to form neural plate.

7. Applied anatomy : Following are the anomalies ¾ Neurogenetic canal: Notochord partly remains patent. It connects to intestinal lumen to central canal of spinal cord. ¾ Notochordal cells in body of vertebrae proliferate to form chordoma. SN-14

Connecting stalk

Introduction: It is a part of extra-embryonic mesoderm which is not encroached by extra-embryonic coelom. 1. Formation (Fig. 5.2) A. As the embryo grows, size of stalk becomes relatively small. B. Gradually, the attachment is shifted to the caudal end of embryonic disc. C. With the rotation of tail fold, attachment of the stalk moves and gets attached to region of umbilical opening. D. The blood vessels develop in embryo and placenta. E. The blood vessels of the placenta communicate with the blood vessels of the mother. 2. Contents A. Two umbilical arteries and one umbilical vein. B. The vitellointestinal duct may remain as remnants of yolk sac. C. The mesoderm of connecting stalk forms a gelatinous substance called Wharton’s jelly. 3. Functions A. It protects umbilical vessels. B. It forms small part of the extra-embryonic coelom. C. It increases the length of the umbilical cord to allow free movement of the embryo. D. It suspends embryo. E. It nourishes embryo. F. It provides space for physiological hernia. 4. Fate: It gets converted into umbilical cord.

1 General Embryology

6. Fate: It does not have any contribution for formation of vertebra. It remains as ANC A. Apical ligament of dens. B. Nucleus pulposus of the intervertebral disc. C. Coccygeal body

28

Exam-Oriented Anatomy

General Embryology

1 Fig. 5.2: Structures forming the umbilical cord

SN-15

Umbilical cord

Introduction: It is a cord extending from umbilicus of fetus to the placenta. 1. Embryonic tissue: After folding of embryo, connecting stalk elongates and forms umbilical cord. 2. Dimensions A. Length: 50 cm B. Diameter: 1–2 cm 3. Content (Fig. 5.3) A. Vessels a. Two umbilical arteries. b. One umbilical vein. B. Mesoderm: Intra-embryonic mesoderm called Wharton’s jelly. C. Remnant structures: Vitellointestinal duct and allantois. D. Layer of amnion.

Fig. 5.3: Structures in the umbilical cord

4. Functions A. It suspends fetus into amniotic cavity. B. It transfers nutrients.

Embryonic Disc

29

5. Knots of umbilicus: These are A. True knots of umbilicus: These are due to excessive movements. B. False knots of umbilicus: These are due to sharp bend of the cord. SN-16

Intra-embryonic mesoderm (secondary mesoderm)

1 General Embryology

Introduction • It forms the 3rd germinal layer. • It is present between ectoderm and endoderm (Fig. 5.4).

Fig. 5.4: Formation of intra-embryonic mesoderm

1. Chronological age: It is formed in the 3rd week of gestation. 2. Sources: The cells of A. Primitive streak. B. Prochordal plate. C. Neural crest. 3. Derivatives of mesoderm (Fig. 5.5) A. Paraxial mesoderm a. Somites I. Sclerotome i. Vertebrae, ii. Portions of the neurocranium, and iii. Axial skeleton. II. Myotome: All voluntary muscles of the head, trunk and limb. III. Dermatome: Dermis of skin over the dorsal region. b. Neuromeres (head mesoderm): Endosteal layer of dura mater. B. Intermediate cell mass or column. a. Connective tissue of the gonads. b. Mesonephric and metanephric nephrons. c. Smooth muscles and connective tissues of the reproductive system.

30

Exam-Oriented Anatomy

General Embryology

1

Fig. 5.5: Fate of intra-embryonic mesoderm

C. Lateral plate or column a. Septum transversum: It gives rise to I. Structures related to heart, i. Epicardium ii. Fibrous pericardium II. Structures related to liver, i. Sinusoids of liver ii. Falciform ligament III. Central tendon of the diaphragm, and IV. Oesophageal mesentery. b. Splanchnopleuric layer: It gives rise to smooth muscle and connective tissues of the I. Intestinal tract and associated glands. II. Respiratory tract and associated glands. c. Somatopleuric layer I. Appendicular skeleton, II. Connective tissue of limbs and trunks (It includes cartilage, ligament and tendons.),

Embryonic Disc

31

III. Dermis of the ventral part of the body and limbs, and IV. Mesenchyme of external genitalia. d. Angiogenic mesoderm I. Endocardium of the heart. II. Endothelium of the blood and lymphatic vessels. Allantois

(allantois—sausage, eidos form) Introduction: It is the diverticulum developing from the hindgut of the fetus. 1. Evolution A. It is tubular ventral diverticulum in embryos of reptiles, birds and mammals. B. It is expanded to a large sac for storing urine in reptiles and birds. C. It is prominent in some mammals (carnivores and ungulates) D. It is vestigial in man. 2. Formation: Before the formation of tail fold, a small endodermal diverticulum arises from the yolk sac near the caudal end of the embryonic disc. This diverticulum grows into the mesoderm of the connecting stalk. After the formation of the tail fold, part of this endoderm is absorbed into the hindgut. It passes from the ventral side of the hindgut into the connecting stalk. The developing bladder is continuous with the allantois. The allantois atrophies and is seen in postnatal life as a fibrous band termed as urachus. The urachus extends from the apex of the bladder to the umbilicus as median umbilical ligament (Fig. 5.6). 3. Anomalies A. Patent urachus: Urachus may remain patent and urine may pass through the umbilicus. B. Urachal cyst: It results from partial persistence of the intra-embryonic allantois. The secretory activity of the linings of allantois produces the dilatation (cyst).

Fig. 5.6: Allantois

1 General Embryology

SN-17

32

Exam-Oriented Anatomy

C. Urachal sinus: The lumen of the lower part of allantois persists. It causes urachal sinus. The sinus is usually continuous with the urinary bladder. D. Urachal fistula: An abnormal passage is formed from a patent urachus. It communicates with the umbilicus and urinary bladder. SAQ-3

General Embryology

1

Septum transversum

1. Introduction: It is unsplit part of lateral plate mesoderm. It is present cranial to the prochordal plate and intra-embryonic coelom. 2. Derivatives of septum transversum A. Structures related to heart a. Epicardium b. Fibrous pericardium B. Structures related to liver a. Sinusoids of liver, and b. Falciform ligament. C. Central tendon of the diaphragm D. Oesophageal mesentery

6 The Placenta

SN-18

Implantation

Introduction: The process by which blastocyst gets embedded in the endometrium is called implantation. 1. Time: On 7th day after fertilization. 2. Site: Endometrium of posterior wall of fundus of uterus (Fig. 6.1).

Fig. 6.1: Normal and abnormal sites of implantation

3. Cells: The responsible cells are cells of trophoblast. They have the property of adhesion, invasion and erosion. 4. Types of implantation (Fig. 6.2) are A. Interstitial: The blastocyst is embedded into stratum compactum of endometrium, e.g. human. B. Central: The blastocyst is embedded in the cavity of uterus, e.g. cow. C. Eccentric: The blastocyst is embedded in the crypts of uterus, e.g. rat. 33

34

Exam-Oriented Anatomy

General Embryology

1 Fig. 6.2: Types of implantation

5. Pre-requisite A. Dissolution of zona pellucida. B. Preparation of the endometrium. It is facilitated by progesterone, which is secreted by corpus luteum. This is called decidual reaction. 6. Actual process A. The zona pellucida disappears. B. The trophoblast adheres to endometrium. C. The trophoblast penetrates endometrium by proteolytic action. D. The cells of the trophoblast proliferate. 7. Results of implantation A. Trophoblast differentiates into two layers a. Cytotrophoblast, and b. Syncytiotrophoblast. B. Inner cell mass differentiates into epiblast cells, hypoblast cells with amniotic cavity and yolk sac cavity. 8. Abnormal sites of implantation of the ovum A. Implantation within the uterus a. Placenta praevia (prae—infront): The placenta is attached to lower uterine segment completely or partially. It is characterized by painless haemorrhage in last trimester particularly in the 8th month of pregnancy. B. Implantation outside the uterus a. Tubal, b. Cervical, c. Peritoneal, and d. Ovarian. 9. Applied anatomy : Excessive or deeper implantation results into postpartum haemorrhage, e.g. ¾ Placenta accreta: It is abnormal adherence of part or whole placenta to the uterine wall. It may or may not have decidua basalis.

The Placenta

35

¾ Placenta increta: Placenta accreta with penetration of myometrium is called placenta increta. ¾ Placenta percreta: Placenta accreta with invasion of the myometrium and peritoneal cavity. It may invade other structures such as bladder. Blastocyst

Introduction: A blastula having a fluid-filled cavity is called blastocyst (Fig. 6.3). 1. Chronological age: It is formed between 4th to 5th day of fertilization. 2. Parts A. Blastocoele, and B. Inner cell mass (embryoblast). C. Trophoblast. 3. Formation: Cells of morula are of two types. A. Cells forming the embryoblast: They give rise to embryo proper. B. Trophoblast cells: These are subdivided into a. Polar cells: They give rise to chorion frondosum. b. Mural cells: They give chorion laeve. The cavity of the blastocyst is called blastocoele.

Fig. 6.3: Blastocyst

SN-20

Decidua

Introduction: The uterine endometrium after implantation is called decidua. 1. Decidual reaction: After implantation, the endometrial glands accumulate glycogen and lipid secretion and this is called decidual reaction. 2. Following changes occur A. Nuclei becomes rounded. B. The number of cytoplasmic organelle increases. C. The volume of the cytoplasm increases. D. The vascularity of the cell increases.

1 General Embryology

SN-19

36

General Embryology

1

Exam-Oriented Anatomy

3. Hormones responsible for the changes are A. Progesterone B. HCG (human chorionic gonadotropin). 4. Functions A. It gives mechanical support to the fertilized ovum and forms a suitable site for implantation. B. It provides nutrition to blastocyst. C. The decidua basalis forms maternal part of placenta and takes temporary function of placenta. 5. Parts of decidua (Fig. 6.4) A. Decidua basalis: The portion of the decidua where the placenta is to be formed is called decidua basalis. It is deep to the developing blastocyst. B. Decidua capsularis: The part of the decidua that separates the embryo from the uterine lumen is called decidua capsularis. C. Decidua parietalis: The part lining rest of uterine cavity is called decidua parietalis.

Fig. 6.4: Decidua

6. Fate A. The decidua basalis undergoes marked development and forms the maternal surface of placenta. B. The decidua capsularis and parietalis are stretched and are fused with each other. It undergoes a. Atrophy. With the increase in size of amniotic cavity following changes occur. b. The extra-embryonic coelom obliterates. c. The amnion fuses with chorion. d. The amnio-chorionic membrane (chorion laevae) fuses with decidua capsularis. C. The decidua capsularis disintegrates and fuses with decidua parietalis and obliterates the uterine cavity. At the time of delivery, placenta separates with decidua basalis and parietalis and is delivered.

The Placenta

Placenta

Introduction: The placenta is an important fetal membrane. It acts as a temporary endocrine gland and maintains the pregnancy after 1st trimester. The placenta is a structure by which fetus is attached to the mother and it gives nutrition to the embryo (or fetus) and excretes waste products from fetus to mother. 1. Formation: The placenta is formed from both fetal and maternal sources. Fetal source is chorion frondosum and maternal source is decidua basalis. A. Formation of chorion frondosum: It follows the following stages (Fig. 6.5) a. Primary stem villi: By the beginning of the 3rd week, a Cytotrophoblastic core is covered by a syncytiotrophoblastic layer and thus forms primary stem villi. b. Secondary stem villi: Mesodermal core penetrates the primary stem villi and thus forms secondary stem villi. c. Tertiary stem villi: The blood vessels appear in the mesoderm of secondary villi to form tertiary villi. These vessels establish contact with intra-embryonic circulatory system. d. Cytotrophoblastic shell: The cytotrophoblast emerges through the syncytium of each villus until they reach the maternal decidua where it spreads out to form a layer. Thus, the shell is formed. The cytotrophoblastic shell gradually surrounds the syncytiotrophoblast entirely and attaches the chorionic sac firmly to maternal endometrial tissue.

Fig. 6.5: Chorionic villi

e. Between the villi: Numerous intervillous spaces are formed. The villi on the embryonic pole continue to grow and expand and thus give rise to chorion frondosum. (The villi on the abembryonic pole degenerate and are called chorion laevae). B. Decidua basalis: The decidua over the chorion frondosum is called decidua basalis. Chorion frondosum and decidua basalis together form the placenta. C. The placenta becomes subdivided into a number of lobes by septa that grow into the intervillous spaces from the maternal side. Each of such lobe of placenta

1 General Embryology

SN-21

37

38

General Embryology

1

Exam-Oriented Anatomy

is often called a maternal cotyledon. If the placenta is viewed from the maternal side, the bases of the septa are seen as grooves, while the cotyledons appear as convex areas bounded by the grooves. a. Each lobe contains the number of anchoring villi and their branches. One such villi and its branches constitute fetal cotyledon. The placenta then forms a compact mass. Structures found in the cut section of placenta are b. Amnion c. Chorion d. Choriodecidual space e. Cotyledons 2. Attachment: The placenta is attached mostly in the upper part of the posterior wall of the uterus (Fig. 6.6).

Fig. 6.6: Fundamental structure of placenta

3. Dimensions: At full term. A. Weight: 500–600 g. B. Diameter: 15–25 cm. C. Thickness: 3 cm 4. Functions of placenta A. It exchanges a. Respiratory gases, i.e. O2 and CO2 between fetal and maternal blood. b. Nutrients and metabolic waste products between fetus and the mother. B. It transfers a. Maternal antibodies to the fetus. b. Drug from mother to fetus. C. It synthesizes following hormones a. Human chorionic gonadotropin (HCG). b. Somatotropic hormone. c. Estrogen d. Estradiol. e. Progesterone f. Relaxin

39

D. It detoxifies the toxic substances. E. It connects fetus to the mother. 5. Types: Placenta may be of following types A. According to the position of the placenta a. Placenta parietalis: When placenta lies on the other walls of the uterus than the fundus. b. Placenta praevia. B. According to shape a. Discoid b. Bilobed c. Multilobed

, , ,

d. Circumvallate, and e. Placenta succenturiate (succenturiate—substitute). C. According to attachment of the umbilical cord a. Marginal, b. Velamentous, c. Furcate, and d. Central. 6. Anomalies A. Hydatidiform or vesicular mole: It results from pathological over activity of the trophoblast. It is simple, noninvasive new growth. B. Chorioepithelioma: It is highly malignant tumour. It results when endometrium is too resistant to blastocyst. SN-22

Types of placenta depending upon shape

1. Lobed: When the placenta is divided into lobes (Fig. 6.7).

Fig. 6.7: Lobed

2. Bidiscoidal: It consists of the two discs (Fig. 6.8).

1 General Embryology

The Placenta

40

General Embryology

1

Exam-Oriented Anatomy

Fig. 6.8: Bidiscoidal

3. Circumvallate: The peripheral margin of placenta is surrounded by a sulcus and overlapped by circular fold of decidua (Fig. 6.9).

Fig. 6.9: Circumvallate

4. Placenta succenturiate: A small placenta is connected with main placenta by blood vessels and membranes (Fig. 6.10).

Fig. 6.10: Placenta succenturiate

SN-23

Types of placenta depending upon attachments

According to attachments of the umbilical cord 1. Marginal (Fig. 6.11): When the umbilical cord is attached close to the margin of placenta. This type of placenta is called battledore placenta. (Battledore racket used to strike the shuttle cock in play.)

41

Fig. 6.11: Marginal

2. Velamentous (membranous or veil-like): When the cord fails to reach the placenta and is attached to the fetal membrane close to the periphery of the organ (Fig. 6.12).

Fig. 6.12: Velamentous insertion

3. Furcate (furca—fork): When the blood vessels divide before reaching the placenta (Fig. 6.13).

Fig. 6.13: Furcate

4. Central: When the cord is attached nearer the centre. This is normal type. SAQ-4

Placenta praevia

Introduction: Implantation of placenta in lower uterine segment is called placenta praevia. 1. Degrees of placenta praevia A. First degree (Fig. 6.14): The attachment of placenta extends into lower uterine segment but does not reach internal os.

Fig. 6.14: First degree

1 General Embryology

The Placenta

42

Exam-Oriented Anatomy

B. Second degree: The margin of the placenta reaches the internal os but does not cover it (Fig. 6.15).

General Embryology

1 Fig. 6.15: Second degree

C. Third degree: The edge of the placenta covers the internal os, but when the os dilates during child-birth, the placenta does not occlude it (Fig. 6.16).

Fig. 6.16: Third degree

D. Fourth degree: The placenta completely covers internal os and occludes the os even after it has dilated (Fig. 6.17).

Fig. 6.17: Fourth degree

The Placenta

43

2. Incidence: 1: 200 3. Clinical features: Painless haemorrhage in the last trimester particularly in the 8th month is a diagnostic feature of placenta praevia. It is common in the 3rd and 4th degree of placenta praevia. Chorion

(Chorion—skin) Introduction: The structures which cover the conceptus is called chorion (Fig. 6.18). It resembles skin. It develops from the cells of the trophoblast. 1. Formation: It is formed by A. Trophoblast B. Somatopleuric extra-embryonic mesoderm. 2. Villi are formed as offshoots from the surface of the trophoblast. Villi arising from chorion are called chorionic villi. They grow into the surrounding decidua. They are of two types A. Temporary: These are related to decidua capsularis and are called chorionic laevae. B. Permanent: They are present in the decidua basalis and are called chorion frondosum (bearing villi). They undergo considerable development and form a disc

shaped mass called placenta.

3. Chorionic villi can be subdivided into A. Depending upon the constituent of the villi a. Primary chorionic villi consist of I. Cytotrophoblast. II. Syncytiotrophoblast. b. Secondary chorionic villi consist of I. Cytotrophoblast. II. Syncytiotrophoblast. III. Primary extra-embryonic mesoderm. At the end of 3rd week, secondary villi are converted into tertiary villi. c. Tertiary chorionic villi consist of I. Cytotrophoblast. II. Syncytiotrophoblast. III. Primary extra-embryonic mesoderm. IV. Fetal blood capillaries. B. According to the branching pattern, the villi may be a. Truncus chorii: Stem b. Rami chorii: Branches c. Ramuli chorii: Finer branches—Ramuli are attached to the cytotrophoblastic shell.

1 General Embryology

SN-24

44

Exam-Oriented Anatomy

General Embryology

1 Fig. 6.18: Chorion

4. Anomalies A. Hydatidiform or vesicular mole (hydatidiform resembling hydatid cyst, hydatid a drop of water) results from pathological overactivity of the trophoblast. It is simple, non-invasive new growth. This is because of failure of vascularization of placental villi. Most moles are benign but 15% invade and destroy myometrium. Incidence 1: 2000 The diagnosis of the hydatidiform mole is made by a. The estimation of high level of chorionic gonadotrophin hormone, and b. Ultrasonography which reveals absence of embryo. Treatment: It does not abort spontaneously. It must be removed surgically. B. Chorioepithelioma: It is highly malignant tumour. It results when endometrium is too resistant to blastocyst. It consists of uncontrolled proliferation of cytotrophoblastic cells result in disorganized masses of invasive tissue. There is rapid metastasis to many other organs, including the lungs and brain. SN-25

The maternal–fetal barrier

1. The maternal–fetal barrier consists of several structures separating maternal and fetal blood. The structures forming placental barrier are (Fig. 6.19): A. Maternal structures a. Maternal erythrocyte membrane b. Maternal blood B. Placental structures a. Syncytiotrophoblast b. Cytotrophoblast c. Cytotrophoblast basement membrane d. Villous connective tissue

The Placenta

45

Fig. 6.19: Structures forming placental barrier

C. Fetal structures a. Fetal capillary basement membrane, b. Fetal capillary endothelium, c. Fetal blood, and d. Fetal erythrocyte membrane. 2. As the placenta grows, the nature of the barrier between maternal and fetal blood also changes. This barrier is reduced in various ways A. The cytotrophoblast continuously divides and fuses to form the syncytiotrophoblast. It is no longer present as a barrier to diffusion. B. The connective tissue stroma becomes spongier. C. The fetal blood vessels migrate from the center of villi toward the periphery. They displace intervening connective tissue elements. 3. The end result: The barrier between fetal and maternal blood is hardly 1 μm thick. 4. Applied anatomy ¾ Immunity from mother to fetus. ¾ Protection of fetus from syphilis in 1st trimester.

General Embryology

1

7 Urogenital System

SN-26

Coelomic wall epithelium

Introduction: Walls of intra-embryonic coelom.

Fig. 7.1: Coelomic wall epithelium

1. Derivatives of coelomic wall epithelium A. Primitive pericardium: Myocardium, parietal pericardium. B. Pericardio-peritoneal canals: Visceral, parietal and mediastinal, pleuroperitoneal membrane contributing to diaphragm. C. Splanchnopleuric epithelium a. Visceral peritoneum of stomach, b. Peritoneum of lesser and greater omenta, c. Falciform ligament, d. Lienorenal, and e. Gastrosplenic ligaments. D. Somatopleuric epithelium: Parietal peritoneum. E. Primitive peritoneal cavity. F. Splanchnopleuric epithelium a. Visceral peritoneal covering of mid- and hindgut, 46

b. Mesentery, c. Transverse, and d. Sigmoid mesocolon. G. Pronephros a. Epithelial lining of mesonephric ducts, b. Ductus deferens, c. Epididymis, d. Seminal vesicles, e. Ejaculatory duct, f. Ureters, and g. Vesical trigone. H. Mullerian ducts a. Epithelial lining of uterine tubes, b. Body and cervix of uterus, c. Vagina, d. Broad ligament of uterus. I. Germinal epithelium of gonad. J. Germinal epithelium forming cortex of adrenal gland. K. Somatopleuric epithelium: Parietal peritoneum, tunica vaginalis of testis. SAQ-5

Surface ectoderm epithelium

Introduction: It is the epithelium lining the ectoderm (Fig. 7.2). 1. Derivatives A. Ectodermal placodes, and B. Adenohypophysis. C. Cranial sensory ganglia of nerves a. V, b. VII, c. IX, and d. X

Fig. 7.2: Surface ectoderm epithelium

47

1 General Embrology

Urogenital System

48

Exam-Oriented Anatomy

D. Olfactory receptor cells, and E. Olfactory epithelium. F. Epithelial walls of the a. Membranous labyrinth, b. Organ of Corti.

General Embrology

1

G. Lens of the eye. H. Enamel of the teeth. I. Secretory and duct lining cells of the a. Lacrimal, b. Nasal c. Labial, d. Palatine, e. Oral, and f. Salivary glands. J. Epithelia of the a. Cornea, and b. Conjunctiva. K. Epithelial lining of the a. External acoustic meatus, and b. External epithelium of the tympanic membrane. L. Epithelial lining of the a. Paranasal sinuses, and b. Oral cavity I. Lips, II. Cheeks, III. Gums, and IV. Palate.

8 Nervous System

SN-27

Neural crest

Introduction: It is ectoderm present at the junction of neural tube and rest of the ectoderm.

Fig. 8.1: Neural crest

Neural derivatives 1. Sensory neurons of the cranial ganglia V, VII, VIII, X and XI. 2. Sensory neurons of the spinal dorsal root ganglia and their peripheral sensory receptors. 3. Satellite cells in all sensory ganglia. 4. Sympathetic ganglia and plexuses: Neurons and satellite cells. 5. Parasympathetic ganglia and plexuses: Neurons and satellite cells. 6. Enteric plexuses: Neurons and glial cells. 7. Schwann cells of all the peripheral nerves. 8. Medulla of the adrenal gland, chromaffin cells. 9. Carotid body type I cells (type II, satellite type cells). 10. Calcitonin: Producing (C cells) 11. Melanocytes. 12. Odontoblast. 13. Leptomeninges. 14. Head mesoderm, etc. 49

2 Genetics

• Chromosomes and their Aberrations • Mendelian Genetics

Attention Please All the text in boxes are not to be written in the examination.

9 Chromosomes and their Aberrations

SN-1

Gene

Introduction: It is the hereditary unit formed by segments of DNA (deoxyribonucleic acid). 1. Function: It synthesizes the polypeptide. 2. Number: There are about 80,000 genes in a human cell. 3. Composition A. Deoxyribose sugar, B. Nitrogen bases, and C. Phosphates. 4. Parts A. The functional part is called exon. B. The silent part is called intron. 5. Position A. Locus: It is the position of the genes on chromosome. B. It is described in relation with centromere. C. Alleles (allos—another): Any alternative form of a gene that can occupy a particular chromosomal locus. 6. Types A. Regulator gene. a. It represses (prevents) the activities of genes. b. It inhibits protein synthesis. B. Operative gene. a. Site: It is present at one end of particular gene. b. Function: A gene that serves as a starting point for reading the genetic code and controls the activity of the structured genes by interacting with repressor. C. Dominant gene: It expresses its physical or biochemical trait, when allelic genes are either homozygous or heterozygous, e.g. 53

54

Exam-Oriented Anatomy

a. The person showing brachydactyly, the prominent genes are NB, BB. b. The tallness is caused by dominant gene, the genotype of the tall individual is T: T, T: t. D. Co-dominant gene: When both allelic genes are dominant but of two different types, both traits may have concurrent expression. E. Recessive gene: It expresses its biochemical and physical traits only in homozygous state, e.g. albinism which is recessive. F. Sex-linked gene a. Abnormal gene located on X or Y chromosome. b. ‘X’ linked inheritance is more common and is mostly expressed by recessive gene. G. Sex limited gene: Born by autosomes but trait is expressed in one of the sex, e.g. gout, baldness.

Genetics

2

H. Carrier gene: Heterozygous recessive gene acts as carrier gene. It may be expressed in subsequent generation. SN-2

Barr body (sex chromatin)

Introduction: It is an inactivated X chromosome attached to nuclear membrane. It is found by Barr and Bertram in 1949.

Fig. 9.1: Barr body

1. Morphology A. Site: It is attached to nuclear membrane. B. Nature: Heterochromatin (State of chromatin in which it is dark staining and tightly coiled, forming irregular clump or Barr bodies in the nuclei of cells in interphase.) C. Shape: Planoconvex D. Dimension: 1 μ E. Staining: Darkly stained F. In female

XX

G. In male (XY). There is only one X chromosome which is for cellular function. Y chromosome is for the determination of sex. Hence, there is no Barr body.

55

Chromosomes and their Aberrations

2. Person with XO will be female as the Y chromosome is absent. The only X chromosome that is present will be in an extended stage and no Barr body is seen. A. The inert X chromosome (Barr body) also divides during cell division. This Barr body is also known as sex chromatin. a. Cell + Barr body = Chromatin positive b. Cell – Barr body = Chromatin negative 3. Appearance: It appears by 2nd week of gestation. 4. Lyon’s hypothesis: The number of Barr bodies is less than the total number of X chromosome. Number of X chromosome – 1 = Number of Barr bodies, e.g. with XX chromosome, there is a Barr body.

B. In male with XY chromosome, there is no Barr body. The absence of Barr body is not enough to prove that cell is from a male

.

Table 9.1: Number of Barr bodies in different syndromes Name of chromosomes

Number of Barr bodies

• XX

• One

• XY

• No Barr body

• XXX

• 2

• Triple XXX

• XXY

• 1

• Klinefelter’s

•X

• 0

• Turner’s

• XO

Syndrome – –

–

5. Applied anatomy ¾ It is helpful for the determination of sex in case of genital ambiguity. ¾ It is a supplementary test in chromosomal aberrations. ¾ It is helpful for diagnosis of various syndromes. SN-3

Structure of chromosome

1. All chromosomes consist of two parallel identical filaments called chromatids. 2. They are joined together at narrowed constriction called primary constriction. Inside the primary constriction, there is a pale staining region called centromere. 3. Free ends of chromatids are called telomeres. Each chromatid is divided by centromere in two arms. 4. In certain chromosomes, there is another narrowing (constriction) near 1 end of each chromatid called secondary constriction. It is stained faintly. If secondary constriction is close to telomere, then the terminal knob of chromosome is termed as satellite (companion). As per the position of centromere, chromosomes are grouped in 4 types (Table 9.2 and Fig. 9.2).

2 Genetics

A. In female

56

Exam-Oriented Anatomy

Table 9.2: Types and position of chromosome Type

Position of centromere in chromosome

• Metacentric

• Middle

• Submetacentric

• Between midpoint and end of the chromosome

• Acrocentric

• Near one end

• Telocentric

• At one end not seen in humans

Genetics

2 Fig. 9.2: Types of chromosomes

5. The chromosome arranged in descending order of length. The pair No. 1 is the longest and the pair No. 22 is the shortest. They are grouped into 7 groups. They are denoted as A to G. Table 9.3: Classes of the chromosome Group

Chromosome number

Features

•A

• 1 to 3

• Large, metacentric

•B

• 4 and 5

• Large, submetacentric

•C

• 6 to 12

• Medium sized, submetacentric

•D

• 13 to 15

• Medium sized acrocentric with satellite

•E

• 16 to 18

• Short submetacentric

•F

• 19 and 20

• Short metacentric

•G

• 21 and 22

• Very short acrocentric

6. Sex chromosomes are X and Y, X belongs to C group and Y belongs to G group. 7. Each cell contains fixed number of chromosomes, which is characteristic of that species or organism. 8. In somatic cell (body cell) of man, the number is 46, which is diploid number. 9. In germ cell, i.e. ova and sperms, the number is 23, called haploid number. When fertilization takes place, union of two haploid cells restores diploid number of fertilized ovum. The number of sets is termed as ploidy. If more than two sets are present, the cell is said to be polyploid. Chromosomes are in multiples of haploid number that is tetraploid (tetra—4) it has 4 times haploid number of chromosomes. Triploid (tri—3) number of chromosomes will be 69, i.e. 3 times the haploid number.

57

Chromosomes and their Aberrations

Classification of chromosomes

(Chrom—colour, soma—body) 1. Structure: Each chromosome is made up of two identical parallel filaments called chromatids, which are held together at a narrow-constricted region, usually pale staining, known as primary constriction, or centromere or kinetochore. This structure is visible only during metaphase stage of cell division. A. Chromosome consists of a. Centromere: The constricted part in chromosome is called centromere. b. Telomere: Free ends (arms) of chromosome. c. Satellite body: Part distal to secondary construction. 2. Function of chromosome is for perpetuation of species. 3. Classification A. According to functions a. Autosomes: 22 pairs in human. b. Sex chromosomes decides the sex of a person. —XY I. Male II. Female

—XX

B. According to the positions of the centromere (Denver’s classification). Table 9.4: Positions of the centromere No. Particulars

Metacentric

Submetacentric

Acrocentric

Telocentric

1.

Centromere

Centrally

Subcentrally

Near one end

At one end so that chromatid has only one arm.

2.

Arms

Equal

p arm (short) q arm (long)

p arm shortest q arm long

One side arms

3.

Satellite body

–

–

May present

–

4.

Secondary construction

–

–

May present

–

5.

Remark

–

–

–

Not found in human being

6.

Chromatid

Only one arm

4. Applied anatomy : Chromosomes are mapped according to length of arm and position of centromere and it is called karyotyping. SN-5

Chromosomal aberrations

Introduction: It is the change in the structural component of the chromosome or number of chromosome. The deletion of a segment or addition of a segment from other chromosomes results in structural aberration. The change in number leads to numerical aberration. 1. Factors: Following are the factors for the chromosomal variations. A. Late age of parents for conception.

2 Genetics

SN-4

58

Genetics

2

Exam-Oriented Anatomy

B. Genes predisposing to non-disjunction. C. Viral infection during pregnancy. D. Exposure to radiation. E. Autoimmune disease of parents. 2. Types A. Numerical type a. Aneuploidy: 2n + 1, 2n – 1 b. Polyploidy: Multiple of n except 2n, e.g. triploidy. B. Structural type: It causes change in the number or sequence of genes. a. Inversion: It is the chromosomal aberration. It is caused by inverted reunion of a chromosome segment after breakage of a chromosome at 2 points. It results in a change in sequence of genes or nucleotides, e.g. the sequence mnopq may be inverted to mnqop. It may be I. Paracentric: It is on one side of centromere. II. Pericentric: It is surrounding the centromere. b. Deletion (Fig. 9.3): A portion of chromosome is lost, e.g. cri du chat syndrome or Philadelphia chromosome. It may be I. Termination–Interstitial

Fig. 9.3: Deletion

c. Translocation: It is displacement of a portion of one chromosome to another chromosome. It is of two types I. Robertsonian translocation (Fig. 9.4), and II. Reciprocal translocation.

Fig. 9.4: Robertsonian translocation

Chromosomes and their Aberrations

59

d. Insertion

Fig. 9.5: Insertion

e. Ring chromosome

Genetics

2

Fig. 9.6: Ring chromosome

f. Isochromosome g. Duplication SN-6

Chromosome banding

Introduction: The chromosomes are identified by banding technique. 1. Procedure: The chromosomes are treated 1st with trypsin and then stained. All the chromosomes are stained with dark and light regions. The dark regions are known as bands. Position of bands in normal chromosome remains fixed and is different for different chromosomes. 2. Types of banding: Banding can be of different types. A. GTG = Giemsa Trypsin Giemsa banding. B. ASG = Acetic saline Giemsa banding. C. Q = Quinacrine mustard banding. 3. Importance of banding: It helps in A. Identification of individual chromosome. B. Confirmation of deletion and inversion.

60

Exam-Oriented Anatomy

SN-7

Trisomy 21

Introduction: It is most common autosomal abnormality syndrome described by John Langdon Haydon Down 1866. 1. Genotype: Trisomy 21 (Down’s syndrome, Mongolism) 47 XX (+ 21) or 47 XY (+21). 2. Phenotype: It is most common autosomal abnormality. 3. Incidence: 1:650 to 700 newborn. 4. Symptoms and pathophysiology: There are three chromosomes in chromosome no. 21. A. Forms of Down syndrome: There are 3 forms a. Trisomy 21 is most common chromosomal abnormality: Extra copy of or female

chromosome in 21 no. of chromosome. It may be male I. If there is XY in 23 no. of chromosome, it is male

Genetics

2

II. If there is XX in 23 no. of chromosome, it is female

.

. .

b. Translocation Down syndrome: It is less common. It affects 3% of people. c. Mosaic Down syndrome: It affects 2% of people. B. Cause is not known. C. It is the result of a. Non-disjunction: In 95% cases, Down syndrome is the result of non-disjunction. Here chromosomes do not split apart. This can occur in 1st or 2nd stage. b. Robertson’s translocation: In 4% of cases, Down syndrome is the result of Robertson translocation. A chromosome number 21 gets attached to chromosome number 14. An abnormal chromosome is called 14, 21. Here number of chromosomes are 46. c. Mosaic: 1%—cells mixed. 5. Risk factors A. Major risk factors: Maternal age a. The incidence of Down syndrome is 1:1500 in females years old. b. The incidence of Down syndrome is 1:25 in females years old.

who are less than 20 who are more than 45

c. How the maternal age affects the disjunction: In females , all the X chromosomes are formed before birth. As the maternal age advances, the X chromosome also ages. And the frequency of non-disjunction in meiosis increases with age. The number of aneuploidy cells increases with maternal age. B. Minor risk factors for chromosomal variations are a. Genes predisposing to non-disjunction. b. Viral infection during pregnancy.

Chromosomes and their Aberrations

61

2 Genetics

c. Exposure to radiation. d. Autoimmune disease of parents. 6. Clinical features A. Effect on brain B. Affected individual is mentally retarded. C. He may suffer by Alzheimer’s disease. 7. Effect on face A. Flat facial profile B. Nasal bridge is flat. C. Palpebral fissure is slanting upwards at lateral end. D. Epicanthic fold of eyes. E. Maxilla is small. F. Palate is narrow, so the oral cavity cannot accommodate tongue. G. The tongue protrudes out of mouth.

Fig. 9.7: Down syndrome (trisomy 21)

8. Effect on heart: In about 50% of the cases, there is congenital heart disease. There is atrioseptal defect. 9. Effect on gastrointestinal tract: Duodenal atresia 10. Effect on blood: Acute lymphatic leukaemia 11. Reproductive: Sterility in males 12. Physical characteristics A. Simian crease B. Gap between two toes

62

Exam-Oriented Anatomy

13. Investigations A. Blood a. There is decrease of I. Alpha-foetoprotein II. Unconjugated estriol (uE3) b. There is increase of I. Human chorionic gonadotrophin (hCG) II. Inhibin A B. Ultrasound: Nuchal transparency—how much light passes through neck. SN-8

Genetics

2

Turner syndrome (45 X)

Introduction: Described by Turner in 1938. 1. Monosomy 23 A. It is not a recessive nor dominant sex-linked disorder. B. It is loss of one X chromosome C. Incidence: 1:2000 girls D. Aetiology a. Major risk factors: Maternal age I. How the maternal age affects the disjunction: In females , all the X chromosomes are formed before birth. As the maternal age advances, the X chromosome also ages. And the frequency of non-disjunction in meiosis increases with age. The number of aneuploidy cells increases with maternal age. b. Minor risk factors for chromosomal variations are I. Genes predisposing to non-disjunction. II. Viral infection during pregnancy. III. Exposure to radiation. IV. Autoimmune disease of parents 2. Incidence: 1:5000 newborns. 3. Genotype: 45 X 4. Phenotype: In female 5. Clinical manifestations A. Stature—short female B. Mouth—shark-like. C. Lip a. Upper—curved. b. Lower—straight.

, Barr body is absent.

63

Chromosomes and their Aberrations

D. Chest: Shield-like— breast under developed, widely placed rudimentary nipples. E. Genitalia: Small—ovarian dysgenesis infertility F. Most often sterile (infertile) G. In females

, gonads are not developed at puberty.

H. Mental retardation I. It is a genetic disorder that only affects females

.

J. But girl with a Turner’s syndrome has only 45 chromosomes. K. Face more health problems than average female

.

L. Low intelligence. M. Webbing of neck. Klinefelter syndrome (47 XXY)

Introduction: Described by Klinefelter in 1942. 1. Interesting facts A. George Washington has this syndrome. B. One Barr body is present. . C. Commonest chromosomal disorders in male D. An extra X chromosome in male . E. Woman who get pregnant after age of 35 are slightly more likely to have a boy with the syndrome than younger women. F. It is not inherited. These chromosomal changes occur as random events. G. Nondisjunction results in reproductive cell with an abnormal number of chromosomes. 2. How does Klinefelter come about: An egg or sperm cell may gain one or more extra copies of the X chromosome as a result of nondisjunction. If one of the atypical reproductive cells contributes to the genotype of a child, the child will receive an extra X. It is because of nondisjunction. It is failure of paired chromosome to disjoin (separate) during cell division so that both chromosomes go to one daughter cell and none to other. birth. 3. Incidence: It occurs in about 1 in 500 to 1000 baby boys.1:1000 live male 4. Phenotype: Male . 5. Genotype: 47 XXY 6. Signs and tests A. Karyotyping: A test to examine chromosomes in a sample of cells, which can help identify genetic problems. This test can count the number of chromosomes, and different structures in chromosomes. B. Semen test: It is a test to measure the amount and quality of a man’s semen. This test would be completed because the most common symptom is infertility.

2 Genetics

SN-9

64

Genetics

2

Exam-Oriented Anatomy

7. Clinical manifestations A. Abnormal body proportions: Long legs, short trunk. Shoulder equal to the hip size. B. Gynecomastia: Abnormally large breast. C. Infertility D. Sexual problems E. Scanty pubic hair. F. Small, firm testicles. G. Azoospermia. 8. Diagnosis A. Prenatal diagnosis by chorionic sampling or amniocentesis in which fetal tissue is extracted and DNA is examined. B. There is no way to detect carrier of this disorder. C. Karyotyping D. Semen test E. Amount and quality of semen 9. Complications A. Enlarged teeth with a thinning surface (taurodontism) B. ADHD (attention deficit hyperactivity disorder) C. Breast cancer in men D. Depression E. Learning disabilities including dyslexia (disorder involving difficulty in learning to read or interpret words, letters and other symbols). F. Osteoporosis: Bones become fragile and more likely to fracture G. Varicose veins H. Autoimmune disorder a. Lupus b. Rheumatoid arthritis c. Sjogren syndrome 10. The extra X chromosome has many effects on the body particularly on the testis. A. No puberty B. No testosterone C. Size of testis is 1/8th the size. 11. Treatment A. No treatment available to change a person’s chromosomal makeup. B. Testosterone replacement for a. Muscularization b. Positive mental attitude c. Less fat on abdomen d. Body hair e. Infertility

66

Exam-Oriented Anatomy

5. Clinical manifestations A. About brain a. Microcephaly b. Mental retardation c. Intellectual disability B. About face

Genetics

2

a. Abnormal shaped ears b. Premature graying of hair c. Skin tags just in front of the ears and eyes d. Wide set of eyes e. Oblique palpebral fissure f. Saddle nose g. Cat-like cry during infancy. h. Excessive drooling (dribbling of saliva) C. Larynx malformed, high-pitched voice D. General features a. Low birth weight and slow growth. b. Muscular hypotonia. c. Partial webbing or fusing of fingers or toes d. Single line on the palm of the hand e. Slow or incomplete development of motor skills E. Behavioural problem, constipation. F. Feeding problem 6. Diagnosis: Possible to detect it with amniocentesis, chorionic villus sampling or CVS 7. Treatment: No ways to manage the symptoms A. Speech therapy B. Physical therapy C. Special education 8. Fun facts A. Less noticeable as the baby gets older. B. Geneticist–Jerome Lejeune identified. He also identified Down’s syndrome C. The main issue located in band 5P 15.2 D. Not dominant or recessive trait E. 80% of the time defective chromosomes from father’s side. F. It happens randomly. G. It is not hereditary. H. Lifespan: Normal

Chromosomes and their Aberrations

SN-11

67

Nondisjunction

Introduction A. Failure of normal migration of chromosome or chromosomes during anaphase of meiosis I. B. Failure of migration of chromatid or chromatids during meiosis II. 1. Reason: Factors responsible A. Faulty spindle formation. B. Slow movement of chromatid or chromosome during anaphase. C. Radiation, viruses, autoimmune disease, e.g. myasthenia gravis, AIDS. 2. It results in formation of abnormal gametes Flowchart 9.1

Normally each sperm has haploid number. A. In nondisjunction Flowchart 9.2

B. Nondisjunction at 2nd meiotic division Flowchart 9.3

C. Change in number of chromosomes: It can occur in sex chromosomes and autosomes when (n+1) fertilized by n result 2n + 1 chromosomes (trisomy) (n–1) fertilized by n (2n–1) chromosomes (monosomy)

Genetics

2

68

Exam-Oriented Anatomy

Effect of fertilization—abnormal gamete. In meiosis II, if all chromatids go to one side. One daughter cell with 2n and other dies Flowchart 9.4

2n fertilizes by n SN-12

Genetics

2

3n

Aneuploidy

(An —not, eu—good, ploidy—multiplication) If number of chromosomes in body cell is either 1. More than diploid number but not multiple of haploid number, e.g. 47 chromosomes. 2. Less than diploid number but not haploid number, e.g. A. An abnormal X chromosome B. One more autosome goes in other cell during division a. Each of 46 chromosomes is a member of homologous pair. One member of each pair being received from mother, one from father. The members of pairs are called homologues. 22 pairs are similar in males are called autosomes.

and females

and

b. Chromosomes in remaining pairs are sex chromosomes. In female

, sex

chromosomes (X and X) are identical so females

are homogametes. In males

, one is X and other is Y which are unequal, so males are heterogametic. c. Homologous chromosomes in each pair of autosomes are indistinguishable, i.e. two chromosomes forming pair number 5 is not identified separately as they appear same. SN-13

Spectral karyotyping (Sky)

Karyotyping: Analysis of chromosome. 1. Definition: A picture of all the chromosomes in an individual cell, is arranged in homologous pairs. They are sorted according to size. Autosomal chromosomes are arranged first. Sex chromosomes are arranged last. It is also called painting of chromosomes. 2. Spectral karyotyping: Fluorescent tag (dye) is given. They are given by different colours. A. Prerequisite for spectral karyotyping a. Sequence of genome must be known. b. DNA must be in single strand.

Chromosomes and their Aberrations

69

c. Segment wise probe is made. d. Different probes will bind different regions. e. The designing of probe is equally important. f. Complimentary probes are designed. g. Depending upon various colours, we can identify the various chromosomes. h. Hybridization of colours is possible in swapping events. It is good for I. Translocation and II. Substitution of chromosomes 3. Disadvantage of spectral karyotyping: It does not help to find other type of mutation, e.g. A. Inversion of chromosome: The changes are in the same chromosome. B. Duplication of chromosome

5. There are two types of chromosomes A. Autosomal chromosomes: The word “soma” means body. They have influence on body characters. They are associated with structure and function of all cells not associated with sex. There are 44 autosomal chromosomes. B. Sex chromosomes: They determine the sex. There are two sex chromosomes. 6. Importance of karyotyping A. To study differences in chromosome size, shape and structure. B. Determination of sex C. Diagnose chromosomal disorder. a. Mutations b. Trisomy 21—Down’s syndrome c. Sex chromosome D. Chromosomal problems a. Trisomy: Extra copy of chromosome b. Monosomy: Missing copy of chromosome (only 1 copy in zygote) c. Partial addition: Extra part of a chromosome d. Partial deletion: Missing part of a chromosome. e. Inversion: Piece of chromosome breaks off, flips around and reattaches (changes order of gene) f. Translocation: Piece of chromosome breaks of, reattaches to a different chromosome. SN-14

What are genetic disorders?

Introduction: Mapping of chromosomes depending upon length and position of centromere is called karyotyping.

2 Genetics

4. Prerequisite: The cells must be in metaphase. They are black and white chromosomal karyotyping.

70

Exam-Oriented Anatomy

1. Procedure: It is done by the microculture of lymphocytes. The cells are grown in culture media phytohaemagglutinin (PHA). The cell division is arrested in metaphase by adding colchicine. The spreads of the chromosome are counted and photographed. The images of each chromosomes are cut out and arranged as per classification. Karyotyping is done on the basis of A. Total length of chromosomes. B. Position of centromere. C. Relative length of two arms. D. Banding pattern. E. The chromosomes are arranged according to their length in a descending order. Identical chromosomes are paired in kcaryotyping. Then chromosomes paired are numbered 1 to 22 in descending order of length, i.e. pair No.1 is long, pair No. 22 is short. They are grouped into 7 groups. They are noted as A to G. The chromosomes are placed separately.

Genetics

2

Table 9.5: Classes of chromosome Group A

Chromosome number

Features

1 to 3

Large, metacentric

B

4 and 5

Large, submetacentric

C

6 to 12

Medium sized, submetacentric

D

13 to 15

Medium sized, acrocentric with satellite

E

16 to 18

Short submetacentric

F

19 and 20

Short metacentric

G

21 and 22

Very short acrocentric

2. Karyotyping helps to A. Identify pattern of abnormal chromosome. B. Determination of the sex.

3 Abdomen

• Introduction and Osteology • Anterior Abdominal Wall • Male External Genital Organs • Abdominal Cavity and Peritoneum • Abdominal Part of Oesophagus and Stomach • Small and Large Intestines • Large Blood Vessels of the Gut • Extrahepatic Biliary Apparatus • Spleen, Pancreas and Liver • Kidney and Ureter • Suprarenal Gland and Chromaffin System • Diaphragm • Posterior Abdominal Wall • Perineum • Urinary Bladder and Urethra • Female Reproductive Organs • Male Reproductive Organs • Rectum and Anal Canal • Walls of Pelvis Attention Please All the text in boxes are not to be written in the examination. Muscles are represented by original shapes in the body. These are only for the memorization of the muscles. Students are not required to draw such shapes in the examination.

11 Introduction and Osteology

SN-1

Spina bifida

It is a gap present on the back in the midline. It is due to failure of fusion of two neural arches. The meninges and spinal cord may herniate through this gap. Depending upon the contents of the spina bifida, they are named as: 1. Meningocele: It is a protrusion of only meninges. It is in the form of cystic swelling. It is filled by cerebrospinal fluid.

Fig. 11.1: Meningocele

2. Meningomyelocele: It is a protrusion of meninges and spinal cord. 3. Syringomyelocele: It is a protrusion of meninges and spinal cord with dilated central canal (Fig. 11.2) 4. Myelocele: It is a protrusion of the substance of the spinal cord through a defect in the vertebral canal. 5. Spina bifida occulta: There is a failure of fusion of two neural arches, but there is no protrusion. There is no swelling on the surface. This is usually associated with talipes equinovarus (or club foot). In this condition, the foot is inverted, adducted and plantar flexed. 77

78

Exam-Oriented Anatomy

Fig. 11.2: Syringomyelocele

SAQ-1

Sacral hiatus

1. It is the opening present at the lower end of sacral canal. It is formed by failure of fusion of laminae of the 5th sacral vertebra. It is covered by dorsal sacrococcygeal ligament. CSF

Abdomen

3

The structures passing through are Coccygeal nerve, 5th Sacral nerves, and Filum terminale.

Fig. 11.3: Dorsal surface of sacrum showing sacral hiatus.

2. Applied anatomy ¾ The sacral hiatus can be entered by a needle that pierces ƒ Skin, ƒ Fascia, and ƒ Posterior sacrococcygeal ligament.

Introduction and Osteology

79

¾ Caudal anaesthesia ƒ Anaesthetic solution is injected into sacral canal through sacral hiatus. It affects spinal roots emerging from the dural sheath. ƒ The solutions act on the spinal roots of the 2nd, 3rd, 4th, and 5th sacral and coccygeal nerves. ƒ It is used in obstetrics to anaesthetize the perineum. It blocks fibres of pain arising from the cervix of the uterus. 3. Surface anatomy : The sacral hiatus lies about 5 cm above the tip of the coccyx and beneath the skin of the cleft between the buttocks.

Abdomen

3

12 Anterior Abdominal Wall

SN-2

Transpyloric plane (Addison’s plane)

(Trans—across, pyloric—end of the stomach) Introduction: It is a horizontal plane passing through the pyloric end of the stomach. 1. Situation A. It lies midway between suprasternal notch and upper end of pubic symphysis. B. It roughly corresponds with midpoint between xiphisternal joint and the umbilicus. C. Anteriorly, it is at tips of 9th costal cartilages. D. Posteriorly, it is at lower border of L1 (lower border of 1st lumbar vertebra) vertebra. ATM It is recollected by

Fig. 12.1: Transpyloric plane 80

Anterior Abdominal Wall

81

Association memory—Tip Box 12.1 Three vertical lines indicate “transpyloric plane” which is a horizontal plane 1st vertical line indicates “L” of lower. 2nd vertical line indicates the 1st. 3rd vertical line indicates “L” of lumbar.

2. Structures at the transpyloric plane are (Figs 12.2A and B) A. Pyloric end of the stomach. B. Lower end of spinal cord. C. Origin of superior mesenteric artery. D. Lateral aortic group of lymph node. E. Hila of both kidneys. F. Fundus of the gallbladder.

Abdomen

3

Fig. 12.2A: Schematic diagram of the structures at transpyloric plane in parasagittal section

82

Exam-Oriented Anatomy

Fig. 12.2B: Structures at transpyloric plane in coronal section

Visual memory —Tip Box 12.2 ATM: Above structures can be recollected by visualizing structures from posterior to anterior.

A. Spinal cord passes trough vertebral canal which ends at transpyloric plane. B. Anterior to vertebra we have abdominal aorta. The artery arising from abdominal aorta at this plane is superior mesenteric artery.

Abdomen

3

1. First analyze the word “Transpyloric”. The word “transpyloric” indicates a transverse plane present at pyloric end of stomach.

C. The lymph nodes surrounding the aorta are called para-aortic lymph nodes and they are present at this level. D. On both sides of vertebrae, we have kidneys. a. We know, right kidney is at lower level because of presence of liver on right side. The upper border of the hilum of right kidney is at this plane. b. The left kidney is at higher level. Hence the lower border of hilum of left kidney is at this level. c. On right side, we have part of the gallbladder below the inferior border of liver. It is the fundus of gallbladder. OLA-1

1. 2. 3. 4. 5.

Sites of portocaval anastomoses

Anterior abdominal wall Posterior abdominal wall Lower end of oesophagus Lower end of rectum Falciform ligament

Anterior Abdominal Wall

83

Fig. 12.3: Sites of portocaval anastomoses

Caput medusae

(Caput—head, Medusae—Greek myth, female

with snaky hair.)

1. The umbilicus is one of the important sites of portocaval anastomosis. 2. There is anastomosis between tributaries of portal and tributaries of systemic veins. The veins are paraumbilical veins in the falciform ligament (tributaries of portal vein) and A. Subcutaneous veins in the anterior abdominal wall (tributaries of epigastric veins which are tributaries of inferior vena cava) (Fig. 12.4). 3. In case of portal hypertension, the blood from portal tributaries is directed into the caval tributaries causing their dilatation and tortuosity. This condition is referred to as ‘caput medusae’ because of its resemblance to the serpents on the head of Medusa, a mythical lady in Greek mythology.

Fig. 12.4: Caput medusae in the anterior abdominal wall

3 Abdomen

SAQ-2

84

SN-3

Exam-Oriented Anatomy

Inguinal ligament

Synonymous: Inguinal arch, arcus inguinalis, ligament of Poupart. Introduction: It is a thickening of lower border of external oblique aponeurosis. It separates abdomen from thigh. 1. Extent: It extends from anterior superior iliac spine to pubic tubercle. 2. Features A. It is thickening of lower border of external oblique muscle. B. It divides abdomen above and thigh below. C. It extends from anterior superior iliac spine to pubic tubercle. 3. Attachments (Fig. 12.5) A. Upper surface gives attachments to a. Internal oblique in lateral 2/3rd b. Transversus abdominis in lateral 1/3rd c. Cremaster muscle in middle part. B. Fascia lata to lower border.

Abdomen

3 Fig. 12.5: Attachments of inguinal ligament on right side

4. Relations A. Upper grooved part forms the floor of inguinal canal. B. Its lodges a. Spermatic cord in male b. Round ligament of uterus in female 5. Extension A. Pectineal part of the inguinal ligament. It is called lacunar ligament. It is lar in shape. a. Anteriorly: It is attached to the medial end of the inguinal ligament. b. Posteriorly: It is attached to the pecten pubis. It is horizontal in position and supports the spermatic cord. c. Apex is attached to the pubic tubercle.

Anterior Abdominal Wall

85

B. Pectineal ligament (ligament of Cooper): It is an extension of the inguinal ligament. It extends from posterior part of base of lacunar ligament. It is attached to the pecten pubis. C. The reflected part of inguinal ligament extends from inguinal ligament to linea alba. SN-4

Rectus abdominis

1. Proximal attachments: It arises by two tendinous heads as follows A. Lateral head from the lateral part of the pubic crest. B. Medial head from the anterior pubic ligament. C. The direction of the fibres is vertically and upwards.

Fig. 12.6: Rectus abdominis muscle and its attachments on right side

2. Distal attachments: It is inserted along a horizontal line extending from the xiphoid process to the 7th, 6th and 5th costal cartilages. 3. Nerve supply : Intercostal nerves (lower 6 or 7 thoracic spinal nerves). 4. Action: Flexion of the trunk (lumbar spine). LAQ-1

Describe rectus sheath under following heads 1. Formation, 2. Contents, and 3. Applied anatomy.

Introduction: It is an aponeurotic sheath enclosing rectus abdominis and pyramidalis muscles. 1. Formation A. Number: It is one on each side. B. Features (Table 12.1)

Abdomen

3

86

Exam-Oriented Anatomy

Table 12.1: Formation of rectus sheath (Fig. 12.7) Particulars

Anterior wall

Posterior wall

Wall

• Is complete

• Is deficient • Above costal margin • Below arcuate line

Composition

• Variable

• Uniform

Extent

• From the costal cartilage to the pubic symphysis

• From the lower margins of the ribs to the arcuate line

• Aponeurosis of external oblique

• No structures

• Below the costal margin to the arcuate line

• Aponeurosis of external oblique. • Anterior lamina of internal oblique

• Posterior lamina of internal oblique • Aponeurosis of transversus abdominis

• Below the level arcuate line

• External oblique • Internal oblique • Transversus abdominis

• Fascia transversalis

Muscles forming • Above the costal margin

Abdomen

3

2. Contents A. Muscles a. Rectus abdominis b. Pyramidalis. B. Arteries a. Superior epigastric artery, branch of internal thoracic artery. b. Inferior epigastric artery, branch of external iliac artery. C. Veins a. Superior epigastric vein > internal thoracic vein > subclavian vein > superior vena cava. b. Inferior epigastric vein > external iliac vein > common iliac vein > inferior vena cava. D. Nerves: Lower 5 intercostal nerves and subcostal nerve. 3. Applied anatomy ¾ Divarication of recti: In multiparous women and chronic weak children, the upper part of linea alba becomes stretched and gap is produced between two recti. ¾ Supraumbilical median incisions ƒ Advantages: It is bloodless area hence there is less bleeding during operation. ƒ Disadvantages • It leaves a postoperative big scar. • There is a delay in healing of the wound. ¾ Infraumbilical median incisions ƒ Advantages: It prevents ventral hernia.

Abdomen

Fig. 12.7: Sagittal section of right rectus sheath showing formation and contents of rectus sheath at various levels

Anterior Abdominal Wall 87

3

88

Exam-Oriented Anatomy

ƒ Disadvantages • There is delay in healing of the wounds because of the less blood supply. • Big scar is formed. ¾ Advantage of paramedian incision: There is an early healing of wound because of rich blood supply. ¾ Incisional hernia: Hernia through the incision taken for the surgery is called incisional hernia. It may be because of injury to spinal nerves. OLA-2

Name the contents of inguinal canal in male

1. Spermatic cord in male : It enters through the deep inguinal ring and comes out through the superficial inguinal ring of inguinal canal. 2. Ilioinguinal nerve (L1): It lies outside the spermatic cord but inside inguinal canal.

Abdomen

3 Fig. 12.8: Contents of right inguinal canal in male

OLA-3

Name the contents of inguinal canal in female

1. Round ligament of uterus. 2. Ilioinguinal nerve.

Fig. 12.9: Contents of right inguinal canal in female

Anterior Abdominal Wall

LAQ-2

89

Describe inguinal canal under following heads 1. Gross anatomy, 2. Development, and 3. Applied anatomy.

Introduction: It is an oblique passage or canal present in the lower part of anterior abdominal wall for the passage of I. Spermatic cord in male or

3 Abdomen

II. Round ligament of uterus in female . 1. Gross anatomy A. Situation: It is situated just ½” above the midpoint of inguinal ligament. B. Extent: It extends from the deep inguinal ring to the superficial inguinal ring C. Length: 1.5” (4 cm) D. Direction: Oblique, downwards, forwards and medially (same as the direction of fibres of external oblique muscle) (Fig. 12.10A). than female . This is because E. Gender variation: The canal is larger in male . of larger dimensions of testis in male F. Boundaries (Fig. 12.10B) a. Roof is formed by lower arched fibres of internal oblique and transversus abdominis. b. Floor I. Laterally: Grooved surface of inguinal ligament. II. Medially i. Grooved surface of inguinal ligament. ii. Upper surface of lacunar ligament. iii. Attachment of fascia transversalis with the inguinal ligament. c. Anterior wall I. Laterally i. Skin ii. Superficial fascia iii. External oblique aponeurosis iv. Internal oblique II. Medially i. Skin. ii. Superficial fascia iii. External oblique aponeurosis d. Posterior wall I. Laterally i. Interfoveolar ligament: It is a thickening in the fascia transversalis. It is present on the medial side of deep inguinal ring. It is connected above to the transversalis muscle and below to the inguinal ligament.

90

Exam-Oriented Anatomy

ii. Fascia transversalis. iii. Extraperitoneal connective tissue. iv. Parietal peritoneum. II. Medially i. Reflected part of inguinal ligament. ii. Fascia transversalis. iii. Conjoint tendon formed by internal oblique and transversus abdominis. iv. Extraperitoneal connective tissue. v. Parietal peritoneum.

Abdomen

3

Fig. 12.10A: Direction of muscles of anterior abdominal wall. “The directions are shown by hands of the clock. 3 o’clock indicates direction of the transversus abdominis, 4 o’clock indicates direction of external oblique, 11 o’clock indicates direction of internal oblique

Fig. 12.10B: Right inguinal canal and its wall, roof and floor

91

Anterior Abdominal Wall

G. Contents and round ligament of uterus in female . It enters a. Spermatic cord in male through the deep inguinal ring and passes out through the superficial inguinal ring of inguinal canal. b. Ilioinguinal nerve: It is derived from 1st lumbar nerve. In the anterior abdominal wall, it lies in the neurovascular plane between the internal oblique and transversus abdominis muscles. It is content of inguinal canal but it does not enter the canal through deep inguinal ring. It pierces internal oblique muscle and enters the inguinal canal. It passes in front of the spermatic cord and leave the canal through superficial inguinal ring. It supplies the skin of the root of and labium majus in the penis and anterior 1/3rd of the scrotum in male female . It also supplies small area of thigh below the medial end of the inguinal ligament. H. Defensive mechanism of inguinal canal: It is the mechanism by which the abdominal contents normally are prevented from entering the inguinal canal. These are as follows a. Flap valve mechanism: The increased intra-abdominal pressure approximates anterior and posterior walls and obliterates the inguinal canal

.

b. Slit valve mechanism: The contraction of external oblique approximates two cruris of the superficial inguinal ring .

canal as a shutter

.

d. Ball valve mechanism: The cremaster muscle contracts and draws upwards the constituents of the spermatic cord. These constituents aggregate at the superficial inguinal ring and act as a plug for the superficial inguinal ring . e. Superficial inguinal ring is guarded by conjoint tendon and reflected part of inguinal ligament. f. Deep inguinal ring is guarded by fibres of internal oblique. g. Hormones play an important role in maintaining tone of inguinal musculature. 2. Development: The canal is (developmentally) formed by the descent of gubernaculum of testis or ovary. In fetal life, the round ligament of uterus is accompanied by a process of peritoneum. It usually disappears after birth. In female , if it persists after birth, it is called canal of Nuck. 3. Applied anatomy ¾ The inguinal canal is a region of potential weakness in the lower part of anterior abdominal wall. Protrusion of abdominal contents through inguinal canal is called inguinal hernia.

3 Abdomen

c. Shutter mechanism: The contraction of the internal oblique closes the inguinal

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Exam-Oriented Anatomy

¾ If contents are pushed out indirectly through deep inguinal ring > inguinal canal > superficial inguinal ring > scrotum, it is called indirect inguinal hernia (Fig. 12.11). It enters the inguinal canal through the deep ring lateral to the inferior epigastric artery.

Fig. 12.11: Indirect inguinal hernia on right side

Abdomen

3

¾ If the contents are pushed out directly forwards through posterior wall of inguinal canal > superficial inguinal ring > scrotum, it is called ‘direct inguinal hernia’. The direct inguinal hernias pass medial to the inferior epigastric artery and lie medial to the spermatic cord (Fig. 12.12). ƒ Medial direct inguinal hernia, and ƒ Lateral indirect inguinal hernia.

Fig. 12.12: Direct inguinal hernia on right side

¾ Inguinal hernias lie superior and medial to the pubic tubercle. This is in contrast to the femoral hernias which lie inferior and lateral to the pubic tubercle (Fig. 12.13). ¾ Direct inguinal hernias are more frequent in old persons. In old age, muscles become lax due to loss of tone and power. The lax muscles yield easily following a ƒ Heavy strain, ƒ Chronic cough,

93

Anterior Abdominal Wall

Fig. 12.13: Difference between femoral and inguinal hernias in relation to pubic tubercle on right side

ƒ Constipation, and BOO . The causes of

I. Stricture of urethra, II. Meatal stenosis, III. Cancer of bladder, IV. Prostatitis, and V. Prostatic abscess. OLA-4

Lacunar ligament

Introduction: Lacunar ligament is pectineal part of inguinal ligament.

Fig. 12.14: Lacunar ligament on right side

3 Abdomen

ƒ Bladder Outlet Obstruction. It is commonly called BOO are

94

Exam-Oriented Anatomy

1. Features A. It is lar. B. It forms the medial boundary of femoral ring. C. It is strengthened by a. Pectineal fascia, and b. Linea alba. 2. Attachments A. Anteriorly to medial end of inguinal ligament. B. Posteriorly to pectin pubis C. Apex is attached to pubic tubercle. 3. Function: It supports spermatic cord. OLA-5

Attachments to pubic tubercle

1. Medial end of inguinal ligament 2. Medial ends of the loop of cremaster

Abdomen

3 Fig. 12.15: Attachments of right pubic tubercle

SAQ-3

1. 2. 3. 4. 5.

Superficial inguinal ring

Location: It is situated 1 cm above the pubic tubercle. Formation: It is formed in the external oblique muscle. Shape: It is lar in shape. Axis: It is oblique. Dimension A. Length: 1” B. Breadth: ½”. 6. Relations (Fig. 12.16) A. Anterior a. Skin, and b. Superficial fascia. B. Medial: Pubic tubercle. C. Lateral: Inferior crus of external oblique muscle which is attached to pubic tubercle.

Anterior Abdominal Wall

95

D. Posterior a. Conjoint tendon. b. Reflected part of the inguinal ligament.

Fig. 12.16: Boundaries of right superficial inguinal ring

7. Contents A. Ilioinguinal nerve. B. Spermatic cord or round ligament of uterus.

1. 2. 3. 4. 5.

Deep inguinal ring

Location: It is situated 1 cm above the mid-inguinal point. Formation: It is present in the fascia transversalis. Shape: It is oval in shape. Axis: It is vertical. Relations A. Anterior: Arched fibres of transversus abdominis. B. Medial: Inferior epigastric artery.

Fig. 12.17: Superficial and deep inguinal rings on right side

SAQ-5

Coverings of spermatic cord

Coverings of spermatic cord: These are described from superficial to deep (Fig. 12.18). 1. External spermatic fascia: It is formed by external oblique. It covers the cord below the superficial inguinal ring. 2. Cremasteric fascia: It is derived from internal oblique and transversus abdominis muscle. It covers the cord below the level of these muscles.

3 Abdomen

SAQ-4

96

Exam-Oriented Anatomy

3. Internal spermatic fascia: It is derived from fascia transversalis. It covers the cord in the whole extent.

Fig. 12.18: Coverings of spermatic cord

SN-5

Abdomen

3

Spermatic cord

Introduction: Each testis develops in the lower thoracic and upper lumbar regions. It migrates into the scrotum. During its descent, it carries “vas deferens” with its vessels, nerves, etc. It is one on each side. 1. Gross A. Length: 7 cm. B. Extent: It extends from upper pole of testis to the deep inguinal ring. C. Course: It ascends in the scrotum and enters the inguinal canal to the superficial inguinal ring. It passes through the inguinal canal and ends at the deep inguinal ring. 2. Constituents are grouped as (Fig. 12.19) A. Deep to internal spermatic fascia a. “Vas deferens”: It starts at the tail of epididymis. At the upper pole of the testis, it is accompanied by other constituents of the spermatic cord. At the deep inguinal ring, it leaves all the structures and enters the abdomen. b. Artery to vas: It is a branch of inferior or superior vesical artery, which is a branch of anterior division of internal iliac artery. c. Structures in relation to testis I. Testicular artery: It is a branch of abdominal aorta. II. Testicular sympathetic plexus: It is formed by renal and aortic plexus. III. Testicular lymph vessels: They drain into the lateral aortic group of lymph nodes. IV. Pampiniform plexus d. Genital branch of genitofemoral nerve supplies cremaster muscle. B. Between external and internal spermatic fascia: Artery to cremaster, a branch of inferior epigastric artery. C. Out side spermatic cord: Ilioinguinal nerve

Anterior Abdominal Wall

97

Fig. 12.19: Constituents of spermatic cord

3. Applied anatomy ¾ Vasectomy: It is surgical removal of “vas deferens” or portion of it. It is one of the commonest operations done for family planning. ¾ Varicocele: The dilatation and tortuosity of pampiniform plexus in the spermatic cord is called varicocele. It mainly occurs on left side. ¾ Torsion of spermatic cord: Torsion (twisting) of the spermatic cord results in death of testis. Hence, it is a surgical emergency. Hesselbach’s (Trigonum inguinale—Inguinal trigone)

Introduction: It is a lar area presents on the anteroinferior wall of abdomen. 1. Boundaries: It is bounded. A. Medially by the lateral border of rectus abdominis muscle. B. Laterally by the inferior epigastric artery. C. Base by the inguinal ligament. D. Floor by the posterior wall of inguinal canal.

Fig. 12.20: Boundaries of right Hesselbach’s triangle

3 Abdomen

SN-6

98

Exam-Oriented Anatomy

2. Distribution: Inguinal hernia is divided into two types depending upon the relation in the Hesselbach’s

.

A. If hernia is passing lateral to the Hesselbach’s hernia.

, it is called indirect inguinal

, it is called direct inguinal hernia B. If hernia is passing through the Hesselbach’s (i.e. medial to inferior epigastric artery). Direct inguinal hernia is again subdivided into a. Lateral direct inguinal hernia: It lies lateral to obliterated umbilical artery. The contents of direct hernia enter through medial inguinal fossa. b. Medial direct inguinal hernia: It lies medial to obliterated umbilical artery. The contents of the hernia enter through the supravesical fossa. 3. Characters of inguinal hernia passing through Hesselbach’s A. It is acquired. B. It is usually bilateral and occurs in old age.

.

4. Applied anatomy ¾ In long-standing hernia, inferior epigastric artery helps to differentiate between direct and indirect inguinal hernias . ¾ It is anatomical landmark to ƒ Differentiate between direct and indirect hernias, and ƒ Recognize neck of hernial sac.

Abdomen

3

OLA-6

What is inguinal hernia?

The inguinal canal is a region of potential weakness in the lower part of anterior abdominal wall. Therefore, following an increased intra-abdominal pressure, the abdominal contents are pushed out through inguinal canal called inguinal hernia. SN-7

Inguinal hernia

Introduction: It is an abnormal protrusion of abdominal contents through the weak point of abdominal wall. 1. Classification A. Based upon the situation of the contents of hernia. a. Direct (old age): If the contents are pushed out directly forwards through posterior wall of inguinal canal > superficial inguinal ring > scrotum, it is called ‘direct inguinal hernia’. If the hernia is medial to inferior epigastric artery, it is diagnosed as direct inguinal hernia. These are subdivided depending upon the relation to the obliterated umbilical artery. I. Medial: Contents of hernia are medial to obliterated umbilical artery. II. Lateral: Contents of hernia are lateral to obliterated umbilical artery. Refer Fig. 12.12 b. Indirect (oblique): If contents are pushed out indirectly through deep inguinal ring> inguinal canal > superficial inguinal ring into the scrotum, it is called

99

Anterior Abdominal Wall

indirect inguinal hernia. Indirect inguinal hernias enter the inguinal canal through the deep ring. It is lateral to the inferior epigastric artery and lies within the spermatic cord. I. Congenital. II. Acquired. Refer Fig. 12.11. 2. Features A. Inguinal hernia lies superior and medial to the pubic tubercle. This is in contrast to the femoral hernias. B. Direct inguinal hernias are more frequent in old persons. In the old age, muscles become lax due to loss of tone and power. The lax muscles yield easily following a heavy strain, as in chronic cough and constipation. 3. Difference between direct and indirect hernias. Table 12.2: Difference between direct and indirect hernias Direct

Indirect (oblique)

• Direction

• Directed almost straight and forward

• Directed forwards and medially

• Age

• Occurs above the age of 40 years

• Occurs in young adult. It may be congenital

• Cause

• Is due to acquired weakness of abdominal muscle

• Is due to congenital weakness of muscle. There is presence of patent lumen of processus vaginalis

• Course

• Contents are passing directly through superficial inguinal ring

• Contents are passing through deep inguinal ring > inguinal canal > superficial inguinal ring

• Relation

• The neck of the hernial sac lies medial • The neck of the hernial sac lies to the inferior epigastric artery lateral to the inferior epigastric artery

• Occurrence • Usually it is bilateral

• Usually it is unilateral

• Age

• Young subjects.

SN-8

• Old age

External oblique muscle of anterior abdominal wall (Fig. 12.21)

1. Proximal attachments A. Middle part of shaft of lower 8 ribs. B. Upper 4 slips get merged with the lower 4 digitations of serratus anterior. C. Lower fibres get merged with the upper fibres of latissimus dorsi. D. Direction of fibres: Downwards, medially and forwards. 2. Distal attachments: Fibres of the muscles are fleshy in proximal attachments and end in aponeurosis. The aponeurosis ends in A. Xiphisternum B. Linea alba C. Pubic symphysis

3 Abdomen

Particulars

100

Exam-Oriented Anatomy

Fig. 12.21: Right external oblique muscle of anterior abdominal wall

Abdomen

3

D. Pubic crest, and E. Pectinate line of pubis 3. Actions A. Lateral bending of back B. With opposite internal oblique, it brings rotation. 4. Nerve supply : Lower 6 thoracic spinal nerves (T7 to T12). SN-9

Transversus abdominis muscle

1. Proximal attachments: Fibres of the muscles are fleshy in proximal attachments and end in aponeurosis. The fleshy part arises from

Fig. 12.22: Right transversus abdominis muscle

Anterior Abdominal Wall

101

A. Lateral 1/3rd of inguinal ligament B. Anterior 2/3rd of outer lip of ventral segment of iliac crest. C. Thoracolumbar fascia, and D. Inner surface of lower 6 costal cartilages. 2. Direction of fibres: Runs horizontally 3. Distal attachments: Along a line of A. Xiphoid process, B. Linea alba, C. Pubic crest, and D. Pectineal line of the pubis 4. Nerve supply : Lower 6 thoracic nerves and first lumbar nerve.

Abdomen

3

13 Male External Genital Organs

SN-10

Histology of testis

1. Histology A. Mediastinum a. It is posterior thickened part of tunica albuginea. b. It sends fibrous septa to divide the interior into pyramid shaped structures called testicular lobules. B. Testicular lobule contains a. Seminiferous tubules (Fig. 13.1): They are tightly coiled and blind ended. They are 1 to 3 in each lobule. b. Leydig cells are present between seminiferous tubules. c. Germ cells: The details of the germ cell are shown in Table 13.1.

Fig. 13.1: Seminiferous tubule under high magnification 102

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Male External Genital Organs

Table 13.1: Details of the germ cell Cells

Situation

Morphology of cell

Nucleus

• Spermatogonium

• Situated near basal lamina between cells of Sertoli

• Cytoplasm in clear

• Shows network

• Primary spermatocyte

• Situated next to spermatogonium

• Large, spherical

• Shows big nucleus

• Secondary spermatocyte

• Situated on inner side • Smaller size of primary spermatocyte

• Shows division

• Spermatid

• Near the lumen

• Small cell

• Rounded nucleus

• Spermatozoa

• In the lumen

• Cell with tail

• Forms head

d. Cells of Sertoli (sustentacular cells or supporting cells). I. They are pyramidal

in shape.

nucleus with prominent nucleolus. II. They have oval III. Outlines of cell are faint and irregular owing to pressure by neighbouring cells. Descent of testis

1. Chronological descent of the testes • One need to know that at birth (9th month), the testes are in scrotal bag (Table 13.2). • Go on reducing one month for each milestone. • At 4th month, it is at iliac fossa. Table 13.2: At 9th month—scrotal bag Month

Position of testis

9th

Scrotal bag

8th

Superficial ring

7th

Inguinal canal

6th

Deep inguinal ring

4th

Iliac fossa

Digital memory—Tip Box 13.1 How to calculate descent of testis

ATM

I. One needs to know that at birth, the testes (9th month) are in scrotal bag. II. Go on reducing one month for each milestone. III. At 4th month, it is at iliac fossa.

Fig. 13.2: Normal course of descent of testis on right side

3 Abdomen

SN-11

104

Abdomen

3

Exam-Oriented Anatomy

2. Factors responsible for descent of testis: Gonads develop behind peritoneum. They develop from the urogenital ridge in the region of the development of kidneys. The exact cause for descent of testis is not known. However, the factors can be grouped as A. Factors which initiate the descent of testis. a. Abdominal temperature is not suitable for spermatogenesis. Hence, it descends in the scrotal bag where temperature is lower. b. Testicular hormone is the most important force and is the stimulus for the descent of testis. c. Gubernaculum testis is a fibrous band, which extends from the testis to the scrotum. It helps in following ways I. The gubernaculum and the dody wall do not grow in the same proportion. II. It helps to dilate inguinal bursa. III. It provides continuous pathway for the descent of testis. d. Formation of inguinal bursa: It is formed by the out pouching of various layers of abdominal wall into the scrotum. The pouch progressively increases and various layers form the covering of testis. e. Processus vaginalis: This is a diverticulum of the peritoneal cavity. It actively grows into the peritoneal cavity. After the descent of testis, the processus vaginalis lost all its connections with the peritoneal cavity and becomes tunica vaginalis. B. Factors which accelerate the descent of testis. a. Intra-abdominal pressure b. Squeezing action of inguinal muscles when testis enters the inguinal canal. 3. Anomalies of descent of testis: The testis may become arrested at any point along its normal journey from lumbar region to the base of the scrotum. Depending upon its location, it is classified into following types. A. Lumbar, i.e. located in the abdomen (entire failure to descent). B. Iliac, i.e. situated at the entrance of inguinal canal. C. Inguinal, i.e. situated within the inguinal canal. D. Pubic, i.e. situated at the superficial inguinal ring. E. Scrotal, i.e. situated high up in the scrotum. 4. Ectopic testis (mal descent of testis): The testis has successfully completed its intra-abdominal descent but failed to reach the scrotum. Following are the sites of ectopic testis: A. In the superficial fascia of the abdominal wall, above the superficial inguinal ring. B. At the root of penis (pubopenile) C. In the perineum Fig. 13.3: Sites of ectopic testis on right D. Femoral side E. Gluteal

Male External Genital Organs

SN-12

105

Thermoregulation of testis

It is done by 1. Veins of pampiniform plexus: It acts as a counter-current heat exchange mechanism. It maintains the temperature of the testis few degrees below the body temperature. 2. Cremaster muscle: It pulls the testis towards the superficial inguinal ring and plays important role in thermoregulation of testis. 3. Fibromuscular ligament: It extends from dartos muscle to testicular pole. It may play a role in thermoregulation of the testis. SN-13

Blood supply of testis

1. Arterial supply a. Testicular artery I. It is main artery of testis. II. It is a lateral branch of abdominal aorta arising at the level of body of L2 vertebra. b. Artery to the vas: It is a branch of superior or inferior vesical artery and sometimes it supplies the testis.

Abdomen

3

Fig. 13.4: Arteries supplying right testis

2. Venous drainage : Veins emerging from the testis form the pampiniform plexus (Pampinus—tendril). They are arranged into three parts (Fig. 13.5): A. Anterior part is present around the testicular artery. B. Middle part is present around ductus deferens. C. Posterior part is isolated.

106

Exam-Oriented Anatomy

Fig. 13.5: Venous drainage of testis

D. Plexus condenses into a. Four veins at superficial inguinal ring.

Abdomen

3

b. Two veins at deep inguinal ring. c. One vein at posterior abdominal wall. d. These veins accompany the testicular artery. e. Right testicular vein drains into inferior vena cava, and f. Left testicular vein opens into left renal vein. I know why—Tip Box 13.2 Note: Pampiniform plexus of testicular veins acts as a counter-current heat exchange mechanism. By this, the blood in the testes is maintained at a temperature 3–4°C below body temperature.

SN-14

Development of testis

1. Development (Tabel 13.3 and Fig. 13.6) A. Chronological age: It develops in the 7th week of intrauterine life.

Male External Genital Organs

107

Table 13.3: Structures, their germ layer and source of development of testis Germinal layer

Source

• Seminiferous tubules

• Lateral plate mesoderm

• Coelomic epithelium gets thickened and is called the genital ridge. This forms solid sex cords. It gets canalized and form seminiferous tubules.

• Cells of Sertoli • Sustentacular or supporting cells

• Lateral plate mesoderm sex cords

• Non-canalized sex cords of coelomic epithelium forms the cells of Sertoli.

• Interstitial cell (cells of Leydig)

• Intermediate mesoderm

• Local mesoderm, i.e. intermediate mesoderm forms interstitial cells.

• Germ cell

• Endoderm

• Migrate from dorsal wall of yolk sac through dorsal mesentery.

• Tunica albuginea

• Mesoderm

• Mesenchyme surrounding developing testis.

B. Site: In the intermediate mesoderm at the level of 10th thoracic vertebra. C. Anomalies a. Anomalies in number I. Monarchism II. Anorchism: Congenital absence of testis. It may be unilateral or bilateral. b. Anomalies of descent (cryptorchidism) c. Abnormal positions (ectopia): The testis may lie. I. Under the skin of the i. Lower part of the abdomen. ii. Front of the thigh. iii. Penis. II. In the femoral canal. III. In the perineum behind the scrotum. d. The testis may be duplicated. e. The two testes may be fused together.

Fig. 13.6: Development of testis

3 Abdomen

Particulars

108

Exam-Oriented Anatomy

2. Applied anatomy ¾ Hydrocele is a condition in which the fluid accumulates in the processus vaginalis. • Following are different types of hydrocele ƒ Congenital – Vaginal: There is accumulation of fluid in tunica vaginalis. – Infantile: The processus vaginalis closes at the deep inguinal ring. – Hydrocele of cord or encysted: The middle part of processus vaginalis is patent. SAQ-6

Epididymis

It is a comma-shaped body. It is situated along the lateral part of posterior border of testis. It is formed by convolution of tube. It has head, body and tail. 1. Head: It is attached to the upper pole of testis and is composed of 10 to 15 efferent tubules. 2. Body: It is composed of single tubule coiled upon itself and lies on the posterior border of testis. 3. Tail: It is attached by fibrous tissue to the lower pole of testis. It continues as “vas deferens”. 4. Appendix of epididymis: The sessile or pedunculated body arising from the head is called appendix of epididymis. It is remnant of the degenerated part of mesonephros.

Abdomen

3

Fig. 13.7: Epididymis

SN-15

Layers of scrotum

1. Skin of the scrotum is continuation of abdominal skin. 2. Dartos muscle is replacement of superficial fascia. 3. External spermatic fascia is derived from external oblique muscle. 4. Cremasteric fascia: A. It consists of a. Cremasteric muscle, and b. Areolar tissue.

109

Male External Genital Organs

B. It is derived from a. Internal oblique, and b. Transversus abdominis. 5. Internal spermatic fascia is derived from fascia transversalis.

Fig. 13.8: Layers of the scrotum

LAQ-3

Describe the testis under following heads 1. Gross anatomy, 2. Histology (SN-10), 4. Applied anatomy (SN-14).

Introduction: Testes are pair of reproductive glands in male

, present in the scrotal

bag. They are homologous to the ovary in female 1. Gross anatomy A. Shape: Ellipsoid B. Dimension a. Length: 5 cm. b. Breadth: 2.5 cm. c. Anteroposterior dimension: 3 cm. d. Weight: 10 to 14 g C. External features a. Poles: It has upper and lower poles. I. Upper pole is directed upwards and laterally and is connected to the head of epididymis by efferent ductules of the testis. II. Lower pole is directed downwards and medially. The tail of the epididymis is connected by fibrous tissue.

Abdomen

3

3. Development (SN-14), and

110

Abdomen

3

Exam-Oriented Anatomy

b. Borders: It has two borders. I. Anterior border is convex and free. II. Posterior border is separated by a pouch of the tunica vaginalis called sinus of epididymis. Testicular vessels and nerves enter through the posterior border. c. Surfaces: It has two surfaces I. Lateral, and II. Medial. d. Position: It is suspended by the spermatic cord. Left testis is at lower level as compared to right testis. e. Side determination: Sinus of epididymis is present on the posterior border of lateral surface. f. Appendix of testis is fibrofatty tissue present on the upper end of testis. It is remnant of cephalic part of Mullerian duct. g. Coverings of testis: The testis is covered by three coats (Fig. 13.9). I. Tunica vaginalis (tunica—coat, vaginalis—sheath): It represents the lower persistent portion of processus vaginalis. It has i. Parietal layer, which is lined by serous epithelium. ii. Visceral layer, which allows free gliding movement of testis. It is deficient at its posterior border. II. Tunica albuginea (albuginea—white): It is a white, dense fibrous coat covering the testis. It is covered by the visceral layer of tunica vaginalis. It is deficient posteriorly through which testicular vessels and nerves enter. III. Tunica vasculosa (vasculosa—vessel): It is the innermost, vascular coat of the testis lining its lobules.

Fig. 13.9: Coverings of testis

Male External Genital Organs

111

D. Blood supply: Refer SN-13 E. Nerve supply : Sympathetic a. The fibres arise from T10 segment of the spinal cord. b. They pass through the renal and aortic plexuses. c. The fibres carry testicular sensation and are vasomotor in nature.

Abdomen

3

Fig. 13.10: Nerve supply of testes

E. Lymphatic drainage (Fig. 13.11) a. Lymph vessels draining the testis run along the testicular artery. b. They end in the lateral aortic group of the lymph nodes. c. They are situated at the level of 1st lumbar vertebra, i.e. at the transpyloric plane. d. Since testis is developed in the lumbar region, this pathway explains why testicular seminoma disseminates widely and rapidly behind the peritoneum.

112

Abdomen

3

Exam-Oriented Anatomy

Fig. 13.11: Lymphatic drainage of testis

2. Histology: Refer SN-10 3. Development: Refer SN-14 4. Applied anatomy: Refer SN-14

14 Abdominal Cavity and Peritoneum

SN-16

Peritoneal reflection

1. It is divided into A. Parietal peritoneum: Peritoneum covering anterior, posterior and lateral walls of abdomen and pelvis is called parietal peritoneum. B. Visceral peritoneum: The peritoneum covering the organs is called visceral peritoneum. It is named as extent of folds of visceral peritoneum. Table 14.1: Extent of folds of visceral peritoneum Fold of peritoneum

From

To

• Falciform ligament • Lesser omentum • Greater omentum • Transverse mesocolon • Mesentery

• • • • •

• Anterior surface of liver • Lesser curvature of stomach • Transverse colon • Anterior border of pancreas • Small intestine

• Mesoappendix • Rectouterine fold • Vesicouterine pouch

• Appendix • Anterior surface of rectum • Urinary bladder

• Gastrosplenic • Gastrophrenic

• From fundus of stomach • Near cardiac end of stomach, the peritoneum of posterior surface extends

SN-17

Umbilicus Inferior surface of liver Greater curvature of stomach Transverse colon Posterior abdominal wall

• Posterior abdominal wall • Posterior surface of uterus • Anterior surface of body of uterus • Hilum of spleen • Inferior surface of diaphragm

Foramen of Winslow (aditus to lesser sac, epiploic foramen)

Introduction: It is an opening, communicating between lesser sac and greater sac (Fig. 14.1). 1. Size: 3 cm. 2. Disposition: It is vertical displayed. 113

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Exam-Oriented Anatomy

Fig. 14.1: Foramen of Winslow

3. Boundaries (Fig. 14.2) A. Anterior: Right free margin of lesser omentum. It contains from left to right a. Hepatic artery. b. Portal vein (more posteriorly). c. Bile duct. B. Posterior: Structures forming posterior boundary of foramen of Winslow

Abdomen

3

SIT Suprarenal gland (right). Inferior vena cava. Twelfth thoracic vertebra. C. Superior: Caudate process of liver. D. Inferior a. Peritoneum extending from inferior vena cava to 1st part of duodenum. b. Horizontal part of hepatic artery. 4. Applied anatomy ¾ Foramen of Winslow cannot be enlarged since there are important structures situated in anterior wall. ¾ The intestines may herniate through epiploic foramen. ¾ The infection spreads from greater sac to lesser sac or vice versa through foramen of Winslow. ¾ After cholecystectomy due to biliary leakage, if patient sits in left lateral position, the fluid tends to permeate through epiploic foramen and distend the lesser sac. SN-18

Lesser sac (omental bursa)

Introduction: It is the large recess of peritoneal cavity present behind the stomach. 1. Gross A. Location: It lies behind the stomach and the lesser omentum. B. Extends: Into greater omentum. C. Communication: To greater sac through epiploic foramen. 2. Boundaries (Fig. 14.3): Rule of 3. There are 3 structures in each boundary.

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115

Abdomen

3

Fig. 14.2: Boundaries of epiploic foramen

A. Anterior wall—for legend refer Fig. 14.3 a. Posterior layer of lesser omentum—Aa b. Peritoneum on the posterior layer of stomach—Ab c. Posterior of the anterior two layers of greater omentum—Ac B. Posterior wall a. Below transverse colon: Anterior of the posterior two layers of greater omentum—Ba

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Exam-Oriented Anatomy

Abdomen

3 Fig. 14.3: Sagittal section of abdomen showing foramen of Winslow

b. Between transverse colon and pancreas: Posterior most layer of greater omentum fused with superior layer of transverse mesocolon—Bb c. Above pancreas: Anterior layer of posterior two layers continues as parietal peritoneum of posterior abdominal wall—Bc C. Inferior wall: Fusion of inner layer of greater omentum up to the level of transverse colon raises the inferior margin. D. Superior wall a. Reflection of peritoneum from oesophagus to diaphragm. b. Upper end of fissure for ligamentum venosum. c. Upper border of caudate lobe of liver. E. Right margin (from below upwards) a. Right margin of greater omentum. b. Right free margin of lesser omentum containing from left to right.

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117

I. Hepatic artery (left) II. Portal vein more posteriorly III. Bile duct c. Floor of aditus to lesser sac F. Left margin of lesser sac (from below upwards) a. Left margin of greater omentum b. Gastrosplenic c. Lienorenal ligament 3. Functions A. It supports and facilitates the movements of stomach. B. Acts as a bursa. C. It is used by surgeon for operative procedures since it is bloodless area. The strangulated internal hernia is approached through greater omentum. Morison’s pouch

It is also called left extraperitoneal space, right subhepatic space or hepatorenal pouch of Morison (Fig. 14.4). 1. It is intraperitoneal space. 2. Boundaries (Fig. 14.5): It is bounded by A. Anteriorly a. Inferior surface of right lobe of liver b. Gallbladder B. Posteriorly a. Right suprarenal gland b. Anterior surface of upper part of right kidney c. 2nd part of duodenum d. Hepatic flexure e. Transverse mesocolon f. Head of pancreas C. Superiorly: Inferior layer of coronary ligament D. Inferiorly: Peritoneal cavity E. Left: Communicated to omental bursa F. Right: Limited by diaphragm 3. Communication on A. Left: Foramen of Winslow Fig. 14.4: Sagittal section of abdomen showing boundaries of Morison’s pouch B. Right: Abdominal wall

3 Abdomen

SN-19

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Exam-Oriented Anatomy

Fig. 14.5: TS of abdomen showing hepatorenal pouch

4. Applied anatomy ¾ It is most dependent part in supine position.

Abdomen

3 Fig. 14.6: Morison’s pouch

¾ There may be accumulation of pus, blood or fluid in this space. ¾ Liquids and bile from lesser peritoneal cavity pass in this pouch. ¾ It can be drained by a tube inserted through a “stab-wound” made through the abdominal wall just outside the right kidney. SN-20

Douglas’ pouch/pouch of Douglas (rectouterine pouch)

Introduction: It is peritoneal space present between anterior surface of rectum and posterior surface of uterus (Fig. 14.7). It is most dependent part in female . 1. Features A. It is deeper than the male rectovesical pouch. B. It extends laterally and posteriorly to form pararectal fossae on each side of rectum. C. The lateral extensions on each side of the rectum, the pararectal fossae are deeper than the pouch of Douglas.

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119

2. Contents A. Loops of small intestine, and B. Anterior surface of rectum. 3. Functions: The fascia uniting rectum and uterus resists increased intra-abdominal pressure.

Fig. 14.7: Boundaries of rectouterine pouch (pouch of Douglas)

¾ Prolapse of the ovary in the Douglas’ pouch do occur in normal woman. ¾ Abscess in the Douglas’ pouch is painful. ¾ Culdocentesis: The incision is made in the posterior part of the vaginal fornix. It is done for the drainage of a pelvic abscess in the rectouterine pouch and a fluid in the peritoneal cavity (e.g. blood). ¾ Pouch of Douglas may contain abnormal structures like descended inflamed appendix. It may be detected by per rectal examination.

Fig. 14.8: Douglas’ pouch

3 Abdomen

4. Applied anatomy

15 Abdominal Part of Oesophagus and Stomach

SN-21

Blood supply of stomach

1. Arterial supply : It is supplied by A. Left gastric artery, the smallest branch of the coeliac trunk and supplies the largest area of stomach. It supplies upper 2/3rd of the organ. B. Right gastric, a branch of common hepatic artery. It anastomoses with the left gastric artery within the lesser omentum. C. Short gastric arteries: These are branches of splenic artery and supply the fundus of the stomach. D. Left gastroepiploic: It is a branch of splenic artery and reaches the greater curvature. E. Right gastroepiploic: It is a branch of gastroduodenal artery and anastomoses with the left gastroepiploic artery.

Fig. 15.1: Arterial supply of stomach. 120

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121

2. Venous drainage A. Right and left gastric veins are tributaries of portal vein.

Fig. 15.2: Venous drainage of stomach

B. Short gastric and left gastroepiploic veins drain into splenic vein.

Abdomen

3

Fig. 15.3: Representation of branches of portal vein 1. Right hand on the anterior abdominal wall represents portal vein 2. Thumb represents right branch of the portal vein 3. Index finger represents left branch of portal vein

C. Right gastroepiploic vein > superior mesenteric vein.

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Exam-Oriented Anatomy

OLA-7

Bare areas of stomach

1. Posterior surface of stomach near cardiac orifice: It is cranial to the gastrophrenic ligament. 2. Area on the lesser curvature of stomach between anterior and posterior layers of lesser omentum. 3. Area on the greater curvature of stomach between anterior and posterior layers of greater omentum. 4. Area of fundus of stomach between the attachments of gastrophrenic ligament. SN-22

What is the surface mucus cells and how do they differ from neck mucus cells in stomach?

1. Surface mucus cells: The epithelial cells secrete mucus. A mucus film is formed. It covers the gastric mucosa. It protects the mucosa of the stomach from acidic gastric juice. 2. Mucous neck cells: They are present in between the parietal cells of the neck of the gland. They secrete mucus. The nucleus of these cells is basal in location and is round. Table 15.1: Surface mucus and neck mucus cells

Abdomen

3

Particulars

Surface mucus cell

Neck mucus cell

• Situation

• Epithelium

• Between parietal cells of neck

• Secretion

• Mucus

• Mucus

• Cytoplasm

• Pale because of histological preparation • Granular cytoplasm is basally and stains more acidophilic

• Position of nucleus

• Base

• Mucigen droplets

• Present in apical but lost in staining

• Shape of nucleus

• Flat

• Function

• Protects mucosa of stomach from gastric juice

• Stem cell replace mucus cells

• Of surface on every third day

OLA-8

• Basal in location

• Round

• Of neck on every 7th day

Differentiate between fundus and pylorus of stomach histologically Table 15.2: Differentiate between fundus and pylorus of stomach histologically

Features

Fundus and body

Pylorus

Depth of the gastric pit

Less

More

Coiling base of gland

Less

More

Parietal cells

Numerous

Very few

Zymogen cells

Numerous

Absent

Abdominal Part of Oesophagus and Stomach

LAQ-4

123

Describe stomach under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: It is the most dilated part of alimentary system. 1. Gross anatomy A. Location: Stomach lies in the upper and left part of abdomen. It occupies a. Epigastrium, b. Umbilical, and c. Left hypochondriac regions.

Abdomen

3

Fig. 15.4: Location of the stomach

B. External features a. Shape I. Depends upon degree of distension. II. Physique of the individual.

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Exam-Oriented Anatomy

III. Position of adjacent organs IV. It is i. J shaped when stomach is empty. ii. Pyriform

shaped when partially distended.

iii. Steer horn in obese. b. Capacity: It varies with age. I. At birth: 30 ml. II. At puberty: 1000 ml. III. In adult: 1.5 liter. c. Curvatures: It has two curvatures. I. Lesser curvature is concave and forms the right border of the stomach. It provides attachment to lesser omentum. II. Greater curvature is convex and forms the left border of the stomach. It provides the attachment to the i. Greater omentum, ii. Gastrosplenic ligament, and iii. Gastrophrenic ligament.

Abdomen

3

Fig. 15.5: Parts and curvatures of stomach

d. Surfaces: In distended position, it has two surfaces. I. Anterosuperior and II. Posteroinferior. e. Subdivisions: It is divided into two parts by the line extending from incisura angularis (junction of horizontal and vertical parts of lesser curvature of stomach) to the greater curvature. I. The larger part is called cardiac part and the smaller part is called pyloric area. II. Cardiac part is subdivided into fundus and the body.

125

i. Fundus: The area above the horizontal line extending form cardiac orifice to greater curvature. ii. Body of stomach: It lies between the fundus and pyloric antrum. iii. Pyloric antrum: It is 3” in length. iv. Pyloric canal: It is 1” long. It is narrow and tubular. C. Internal features a. Orifice: There are two orifices. I. Cardiac orifice: It is present at the lower end of oesophagus. It is a physiological sphincter. It cannot be demonstrated anatomically. II. Pyloric sphincter (pylorus—gate): It is situated ½” to the right of the median plane, at the lower border of L1 vertebra. b. Mucous membrane I. It is thick, velvety, and has number of temporary fold or rugae. They are in long axis. These folds disappear when the stomach is distended. II. Gastric canal (magenstrasse) is a mucous gutter. It is present on lesser curvature. It extends from the cardiac orifice to the pyloric antrum. D. Relations a. Peritoneal relations: The stomach is covered by the peritoneum everywhere except I. The bare area: It is an area behind the cardiac end of the stomach, which is in contact with the diaphragm. II. At the lesser curvature along the attachment of lesser omentum. III. At the greater curvature along the attachment of i. Gastrophrenic ligament, ii. Gastrosplenic ligament, iii. 1st and 2nd layers of greater omentum.

Fig. 15.6: Folds of peritoneum attached to stomach

3 Abdomen

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Exam-Oriented Anatomy

b. Visceral relations I. Anterior i. Liver, ii. Diaphragm, and iii. Anterior abdominal wall. II. Posterior surface of stomach is related to structures forming the stomach bed. i. Left crus of diaphragm, ii. Splenic artery, iii. Transverse mesocolon, iv. Left colic flexure, v. Anterior surface of the left kidney, vi. Left suprarenal gland, and vii. Body of pancreas. E. Blood supply: Refer SN-21 F. Nerve supply : It is supplied by sympathetic and parasympathetic nerves.

Abdomen

3

a. Sympathetic fibres: They arise from coeliac plexus. The pre-ganglionic motor fibres arise from T6 to T9 segments of the spinal cord and the fibres reach via greater splanchnic nerves. They relay in coeliac ganglion. The sympathetic fibres have following functions. I. They are vasomotor in function. II. They stimulate the pyloric sphincter. III. They inhibit the smooth muscles of the stomach. IV. Sensory sympathetic fibres convey painful sensations from the stomach. b. Parasympathetic fibres: They are derived from both the vagi nerves. They consist of anterior and posterior gastric nerve. The stimulation of the parasympathetic nerve I. Increases motility of the stomach. II. Secretes gastric juice which is rich in pepsin and hydrochloric acid. III. Inhibits pyloric sphincter. G. Lymphatic drainage a. All the lymphatics from the stomach ultimately drains into coeliac group of lymph nodes > intestinal lymph trunk > cisterna chyli. b. It is divided into 4 regions by a vertical line A. It runs in long axis of stomach. The line “A” extends from fundus of stomach to pyloric end of stomach. c. It divides area of stomach into right 2/3rd and left 1/3rd region. d. Left 1/3rd is subdivided by a horizontal line into upper 1/3rd and lower 2/3rd. e. Pyloric region

127

Fig. 15.7: Lymphatic drainage of the stomach Table 15.3: Lymph nodes of the stomach and their afferent and efferent lymphatics Area Lymph nodes

Situation of lymph nodes

Afferent lymphatics

a

• Left gastric nodes

• Lesser curvature of stomach along left gastric artery

• Right 2/3rd of • Coeliac nodes the stomach • Abdominal part of the oesophagus

b

• Pancreaticosplenic

• Upper part of greater curvature of stomach along the short branches of splenic artery

• Pancreas and spleen

c

• Right gastroepiploic lymph nodes

• Lower part of greater • Lower 2/3rd of curvature of stomach the left 1/3rd of along the right gastrothe stomach epiploic artery

• Subpyloric lymph nodes> hepatic lymph nodes > coeliac nodes

d

• Pyloric part

• Lower border of pyloric part of stomach

• They drain in hepatic or directly into coeliac lymph nodes.

• Pylorus of stomach

Efferent lymphatics

• Travel to the coeliac nodes along splenic artery

3 Abdomen

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Exam-Oriented Anatomy

2. Histology : The wall of the stomach presents 4 coats from inside out. A. Mucous membrane: It consists of epithelium, lamina propria and muscularis mucosae. a. Epithelium I. It is tall, simple columnar epithelium. It is honeycomb in appearance and presents numerous depressions of gastric pits. They receive ducts of gastric glands. II. It has i. Thin basement membrane formed by connective tissue. ii. Light staining apical cytoplasm. iii. Dark staining basal nuclei.

Abdomen

3

Fig. 15.8: Histology of fundus of stomach

b. Lamina propria: It contains I. Collagen fibres II. Cells of connective tissue III. Blood vessels IV. Various types of gastric glands.

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The gastric glands are of three types. i. Cardiac glands: They are few in number. They are situated close to cardiac orifice. They secrete mucus. ii. Pyloric glands: They are lined by mucous-secreting cells. Some of the cells secrete the hormone, gastrin. iii. Fundic glands: They are present in fundus and body. They contain three types of cells. * Zymogenic or chief cells. These are cubical and possess basophilic cytoplasm. * Oxyntic cells (parietal cells): These are large polyhedral cells and possess acidophilic cytoplasm. They secrete HCl. * Mucous cells are found in the neck of the gland. c. Muscularis mucosae: It is well developed in stomach. It has two types of smooth muscles I. Inner circular, and II. Outer longitudinal. An additional circular layer may be present outside the circular coat. B. Submucosa a. It consists of loose connective tissue. b. It has I. Blood vessels II. Lymphatics III. Plexus of autonomic nerves (Auerbach’s or myoenteric plexus). C. Muscular coat: It consists of smooth muscles, namely a. Outer longitudinal muscles. b. Inner circular muscles: They are thickened at the pylorus and forms a ring of muscle known as pyloric sphincter. c. Oblique muscles. D. Serous coat: It is lined by simple squamous epithelium of peritoneum (Fig. 15.9). 3. Development: It is described under A. Chronological age: It first becomes apparent at 4th week. The rotation of stomach occurs in 7th week of intrauterine life. B. Germ layer: Endoderm and mesoderm. C. Site: Inferior to septum transversum in lateral plate mesoderm. D. Sources a. The epithelium and the glands of stomach develops as a fusiform dilatation of foregut distal to the oesophagus. b. All the remaining layers of the stomach develop from intra-embryonic splanchnopleuric mesoderm. E. Anomalies: Congenital hypertrophic pyloric stenosis. It is a congenital defect with a neuromuscular incoordination of the thickened pyloric sphincter. The infant suffers from progressive vomiting within 2 weeks to 2 months of postnatal life.

3 Abdomen

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3

Exam-Oriented Anatomy

Fig. 15.9: Histology of pyloric end of stomach

4. Applied anatomy ¾ Gastric pain is felt in epigastrium. The stomach is supplied from segments T6 to T10 of the spinal cord, which also supply skin of the upper part of the abdominal wall. The pain is produced by spasm of muscle, or by over distension.

Fig. 15.10: Site of the referred pain of stomach

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131

¾ Gastric ulcers usually occur along the lesser curvature of stomach. This is because of following factors. • Gastric canal is formed along the lesser curvature of the stomach. During swallowing, the liquid or bolus of the food passes through this canal and thus the gastric mucosa is exposed to irritant liquids and spices in food. This results in gastritis and ulceration. The vessels to the gastric mucosa along the lesser curvature do not arise from a submucous plexus but directly arise from gastric arteries outside the gastric wall. ¾ Truncal vagotomy involves section of the main trunks of both vagi. It should always be accompanied by either pyloroplasty or gastrojejunostomy. ¾ Selective vagotomy is designed to section the nerves of Latarjet of both vagi. ¾ Highly selective vagotomy is the operation of choice because it denervates only those small branches on the left side of both nerves of Latarjet which supply acid-bearing area of the stomach. SN-23

Stomach bed

Acronym of stomach bed—Tip Box 15.1

The structures present on the posteroinferior surface forms the stomach bed. The posteroinferior surface of stomach is covered with peritoneum of lesser sac except bare area. It forms shallow fossa upon which the stomach rests in a recumbent supine position. The bed consists of the following structures. • Main structure is left crus of diaphragm. • Tortuous splenic artery. • When stomach is distended, gastric surface of spleen also comes in contact. The spleen is separated from the stomach by a recess of greater sac. W is inverted M. • Transverse mesocolon. • Left colic Flexure. • Anterior Surface of the left kidney. • Anterior Surface of left suprarenal gland. • Body of the pancreas (Fig. 15.11A and B).

3 Abdomen

The first letter of these structures are the letters of the week days like Monday, Tuesday

132

Exam-Oriented Anatomy

Fig. 15.11A and B: (A) Structures forming stomach bed when stomach is empty; (B) Structures forming stomach bed when stomach is distended

SN-24

Oesophageal varices

Varices (plural of varix): Varix is enlarged tortuous vein, artery or lymphatics.

Abdomen

3

1. Definition: It is varicosities of the branches of the azygos vein which anastomose with tributaries of portal vein in the lower oesophagus, occurring in patients with portal hypertension. 2. Site: Lower end of oesophagus. A. It is one of the important sites of portosystemic anastomoses. The lower end of oesophagus drains into a. Azygos and hemiazygos > superior vena cava a systemic vein. b. Gastric and splenic veins > portal vein. B. Because of portal hypertension, the veins dilate and the dilated veins are called varices.

Fig. 15.12: Oesophageal varices

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133

3. Applied anatomy ¾ It is diagnosed by barium X-ray which shows typical cotton wool appearance. ¾ Endoscopic examination at the lower end of oesophagus is preferred. ¾ It is treated by injecting sclerosing agent on 2 to 3 occasions. ¾ It can be ligated endoscopically by application of bands. ¾ May rupture and cause dangerous or even fatal haematemesis.

Abdomen

3

16 Small and Large Intestines

SN-25

Relations of 1st part of duodenum Table 16.1: Relations of 1st part of duodenum

Features and surface

Structures related

Peritoneal

• Proximal 1”—movable. Covered by peritoneum • Distal 1”—fixed and retroperitoneal

Visceral • Anterior

• Quadrate lobe of liver • Gallbladder

• Posterior

• Gastroduodenal artery • Bile duct • Portal vein

• Superior

• Epiploic foramen

• Inferior

• Head and neck of pancreas

Fig. 16.1: Posterior relations of 1st part of duodenum 134

Small and Large Intestines

SN-26

135

Relations of 2nd part of duodenum Table 16.2: Relations of 2nd part of duodenum Surface

• Peritoneal

• Transverse colon • Above and below the transverse colon, it is covered by peritoneum of greater sac.

Structures related

• Visceral

• Anterior

• Area above the transverse colon is related to – Inferior surface of the right lobe of liver – Body of the gallbladder • Area below the transverse colon is related to – Coils of jejunum

• Posterior

• Anterior surface of right kidney. • Structures at hilum of the right kidney (from anterior to posterior) – Right renal vein – Right renal artery – Pelvis of right ureter • Right margin of inferior vena cava • Psoas major • Crus of diaphragm

• Right border

• Right colic flexure

• Left border

• Right border of head of pancreas • Anastomosis between superior and inferior pancreaticoduodenal vessels • Pancreaticoduodenal lymph nodes. • Left border is pierced by – Bile duct – Pancreatic duct – Accessory pancreatic duct

Fig. 16.2A: Relations of 2nd part of duodenum on left side

3 Abdomen

Features

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Exam-Oriented Anatomy

Fig. 16.2B: Relations of 2nd part of duodenum on anterior, posterior surface and right border

SN-27

Relations of 3rd part of duodenum Table 16.3: Relations of 3rd part of duodenum

Abdomen

3

Features

Surface

Structures related

• Peritoneal

• Retroperitoneal and fixed

• Visceral

• Anterior

• Superior mesenteric vessels • Root of mesentery

• Posterior

• Right ureter • Right psoas major • Right gonadal vessels • Inferior vena cava • Abdominal aorta • Inferior mesenteric artery

• Superior

• Head of pancreas with uncinated process

• Inferior

• Coils of intestine

Fig. 16.3: Sagittal section showing the relations of 3rd part of duodenum

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Small and Large Intestines

SN-28

Relations of 4th part of duodenum Table 16.4: Relations of 4th part of duodenum

Features

Surface

Peritoneal

• Retroperitoneal

Visceral

Related structures

• Anterior

• Transverse colon • Transverse mesocolon • Lesser sac • Stomach

• Posterior

• Left sympathetic chain • Left renal artery • Left gonadal artery • Inferior mesenteric vein

• To the right

• Upper part of root of mesentery

• To the left

• Left kidney and • Left ureter

• Superior

• Body of pancreas

Abdomen

3 Fig. 16.4: Relations of 4th part of duodenum

OLA-9

Peritoneal recesses around duodenum Table 16.5: Peritoneal recesses around duodenum

Recess

%

Situation Deep

• Superior duodenal

• 50

• L2

• 2 cm

–

Direction of orifice • Downwards

• Inferior duodenal

• 75

• L3

• 3 cm

–

• Upwards

• Paraduodenal

• 20

–

–

• Inferior mesenteric vein lies in the fold

• Retroduodenal

• Occasional

–

• 8 to 10 cm

• Largest of all recess

–

–

• Lies behind upper • left part of mesentery • Superior mesenteric vessels lie in the fossa

• Mesenterico- 1 parietal fossa of Waldeyer

Features

• Right

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Exam-Oriented Anatomy

Fig. 16.5: Site and incidence of peritoneal recess around duodenum

LAQ-5

Describe 2nd part of duodenum under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: It is the junction of the foregut and midgut.

Abdomen

3

1. Gross anatomy A. Internal features: The interior of the 2nd part of duodenum shows the following special features. B. Location: It is present in umbilical region on the right margin of 2nd lumbar vertebra. a. Plica circularis: It is longitudinal fold present below major duodenal papilla. b. The major duodenal papilla, I. It is an elevation present posteromedially. II. It is 8 to 10 cm distal to the pylorus. III. The hepatopancreatic ampulla opens at the summit of the papilla. c. The minor duodenal papilla I. It is present 6 to 8 cm distal to the pylorus. II. It has the opening of the accessory pancreatic duct. C. Relations: It is described as a. Peritoneal relations: It is retroperitoneal and most fixed part of duodenum. I. Anterior surface is related to II. Transverse colon. III. Above and below the transverse colon, it is covered by peritoneum of greater sac. IV. Posterior surface is non-peritoneal. b. Visceral relations I. Anterior surface (Fig. 16.6): It is divided into i. Area above the transverse colon is related to

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139

• Inferior surface of the right lobe of liver. • Body of the gallbladder. ii. Area below the transverse colon is related to coils of jejunum.

Fig. 16.6: Anterior relations of 2nd part of duodenum

VAU Right renal Vein Right renal Artery Pelvis of right Ureter iii. Right • Margin of inferior vena cava • Psoas major • Diaphragm III. Right border is related to right colic flexure. IV. Left border is related to head of pancreas in its entire course. i. Anastomosis between the superior and inferior pancreaticoduodenal vessels. ii. Pancreaticoduodenal lymph nodes. It is pierced by • Bile duct, • Pancreatic duct, and • Accessory pancreatic duct. Refer Fig. 16.2B

3 Abdomen

II. Posterior surface i. Anterior surface of right kidney ii. Structures at hilum of the right kidney (from anterior to posterior).

140

Exam-Oriented Anatomy

D. Blood supply a. Arterial supply I. Part of the duodenum above the opening of bile duct is –A. i. It belongs to foregut. ii. The artery of the foregut is coeliac trunk. It gives hepatic artery> gastroduodenal artery > superior pancreaticoduodenal artery which supplies area A. II. Part of the duodenum below the opening of bile duct is B. i. It belongs to midgut. ii. The artery of midgut is superior mesenteric artery > inferior pancreaticoduodenal artery which supplies B. b. Venous drainage I. Superior pancreaticoduodenal vein > portal vein. II. Inferior pancreaticoduodenal vein drains into superior mesenteric vein. E. Nerve supply a. Sympathetic nerves: They arise from spinal segments of T9 and T10. b. Parasympathetic nerves: They arise from vagus nerves. F. Lymphatic drainage : Lymph vessels drain into

Abdomen

3

a. Pancreaticoduodenal lymph nodes. b. Pyloric lymph nodes: The efferent lymphatics go to I. Coeliac group of lymph nodes. II. Superior mesenteric group of pre-aortic lymph nodes.

Fig. 16.7: Lymphatic drainage of duodenum

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141

2. Histology A. Features a. The luminal surface has numerous folds. They project into the lumen. They are called plicae circularis. These folds consist mucosa and submucosa. b. The mucosa shows numerous fingers like projections. They are called intestinal villi. c. Each villus has I. Lamina propria, and II. Epithelium. d. Brunner’s gland in submucosa is the feature of duodenum. It has columnar cells with flat nuclei.

Abdomen

3

Fig. 16.8: Macroscopic structure of duodenum

B. It has four coats. a. Mucous coat containing I. Simple columnar epithelium with intestinal glands. II. Lamina propria. III. Muscularis mucosa.

142

Abdomen

3

Exam-Oriented Anatomy

b. Submucosa containing Brunner’s glands. It secretes alkaline mucus which protects acidic chyli. c. Muscularis externa containing smooth muscles, namely I. Inner circular, and II. Outer longitudinal. d. Serous coat is lined by simple squamous epithelium or adventitia. 3. Development A. Chronological age: It develops in the 4th week of intrauterine life. B. Germ layer: Endoderm and mesoderm. C. Site: Caudal part of foregut. D. Sources a. The epithelium of the 2nd part of duodenum I. Above the opening of bile duct develops from endoderm of the foregut. II. Below the opening of the bile duct develops from endoderm of the midgut. b. All the coats of duodenum except epithelium and glands develop from intraembryonic splanchnopleuric mesoderm. E. Sequence of events: During rotation, the dorsal mesentery disappears except 1’’ near pyloric end and the duodenum becomes retroperitoneal organ. F. Anomalies a. Abnormal fixation: There is no functional disturbance. b. Excessive fixation may cause interference with mobility, kinks, and compression of the lower bowel. c. Failure of fixation may cause ptosis, torsion or volvulus. d. Abnormal rotation predisposes to volvulus, which causes internal obstruction. Such obstruction is particularly likely to occur within the 1st few days of life (volvulus neonatorum). e. During rotation of the stomach, the duodenum also rotates to the right and forms a superior retention band, which fixes it at the junction of duodenum with jejunum. The superior retention band becomes suspensory ligament of duodenum. f. There is temporary blockage of duodenal lumen by proliferation of endoderm. The lumen is re-established after some time. The failure of the formation of the lumen leads to atresia. 4. Applied anatomy ¾ Duodenal diverticula are fairly frequent. They are generally seen at the point of entry of arteries. ¾ Congenital stenosis and obstruction may occur at the site of opening of the bile duct. Other causes of obstruction include • Annular pancreas. • Pressure by superior mesenteric artery. • Constriction of suspensory muscle of duodenum. ¾ Second part is most protected from the external injury, since it is situated behind the forward curvature of the vertebral column in the paravertebral gutter. Sometimes

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143

small bile stones may be impacted on the summit of the major papilla producing obstructive jaundice. SN-29

Duodenal cap

1. Definition: The barium meal X-ray of the digestive tract shows a smooth lar shadow. It is seen in the 1st part of duodenum. It is called duodenal cap. It has a base and an apex. The base is below and apex is above. A. The following anatomical factors appear to be responsible for it. B. The 1st part of duodenum runs upward, backward and to the right to continue as 2nd part. C. The knob-like pylorus invaginates into the 1st part of duodenum. This is kept open and filled with barium paste. D. The mucous membrane of proximal half of duodenum is devoid of circular folds. E. The proximal half of the 1st part of the duodenum is mobile. Because it has mesentery. F. The viscosity of the barium sulphate coming out of a narrow pyloric canal gives a conical appearance.

Abdomen

3 Fig. 16.9: Duodenal cap

SN-30

Ligaments of Treitz (suspensory muscle of duodenum)

Introduction: It is the fibromuscular band extending from right crus of the diaphragm to the duodenojejunal flexure. 1. Formation: It is formed in A. Upper part by striped muscle fibres. B. Middle part by elastic fibres. C. Lower part by smooth muscle fibres. 2. Importance A. It marks duodenojejunal junction. B. If it is attached only to flexure, its contraction may narrow the angle of flexure, causing partial obstruction of gut.

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Exam-Oriented Anatomy

Fig. 16.10: Suspensory muscle of duodenum (ligaments of Treitz)

SN-31

Abdomen

3

Meckel’s diverticulum

Introduction: This is the persistent proximal part of the vitellointestinal duct. 1. Gross anatomy A. Situation: It is located at the anti-mesenteric border of the ileum. B. Rule of 2 a. Length: 2” b. Distance from the ileocaecal valve: 2’. c. Incidence: 2% of population. C. Its caliber is equal to that of ileum. D. Its apex may be free or may be attached to the umbilicus or any other abdominal structure.

Fig. 16.11A: Vitellointestinal duct in early embryo

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Small and Large Intestines

Fig. 16.11B: Meckel’s diverticulum—length, distance from ileocaecal junction and on antimesenteric border

2. Content: It contains A. Pancreatic tissue, and B. Gastric mucosa. 3. Applied anatomy

SN-32

Differences between jejunum and ileum Table 16.6: Differences between jejunum and ileum

S. no.

Features

1.

• Meaning

2.

Jejunum

Ileum

–

• Starvation

• Coiled

• Presence of fat

–

• Less

• More

3.

• Number of windows

–

• More

• Less

4.

• Feel of the wall

–

• Tube in tube

• Single wall

5.

• Circular folds

• Size • Number • Present

• Larger • More in number • Palpated

• Smaller • Less in number • Disappear distally

6.

• Dimension

• Width

• Wider

• Narrow

• Condition

• Empty

• Loaded

7.

Particulars

Contd.

3 Abdomen

¾ It is one of the most common congenital anomalies of the gastrointestinal tract. ¾ It is responsible for intestinal obstruction and intussusception. ¾ It may enter into hernial sac. It is one of the differential diagnoses of appendicitis.

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Exam-Oriented Anatomy

Table 16.6: Differences between jejunum and ileum (Contd.) S. no .

Features

Particulars

Jejunum

Ileum

8.

• Villi

• Length

• Larger

• Short

• Thick

• Thin

9.

• Thickness

10.

• Lymphatic follicle

–

• Present only in • Arranged along long axis— lower part and circularly arranged. Payer’s patches

11.

• Wall

–

• Thick walled

• Thin walled

12.

• Appearance

–

• Red due to more vascularity

• Not red due to less vascularity

OLA-10 Peritoneal recesses around caecum Table 16.7: Peritoneal recesses around caecum

Abdomen

3

Recess

Features

Direction of orifice

Superior ileocaecal

Present between ileum and ascending colon. More common

Looks downward and left

Inferior ileocaecal

Covered by blood less fold of Treves

Retrocaecal

Behind the apex of sigmoid colon. It often contains appendix.

LAQ-6

Looks downward

Describe caecum under following heads 1. Gross anatomy, and 2. Applied anatomy.

Introduction: It is the proximal end of the large intestine where the large and small intestines meet. 1. Gross anatomy A. Location: It is situated in right iliac fossa above the lateral half of inguinal ligament (Fig. 16.12). a. Length × breadth = 6 cm × 7.5 cm. b. Shape: Usually asymmetrical cul de sac. Organs betraying “width” Box 16.1 Note: Organs having more width than length I. Prostate II. Caecum III. Isthmus of thyroid gland

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Small and Large Intestines

Fig. 16.12: Location of caecum

B. Internal structure: It shows two orifices (Fig. 16.13). a. Ileocaecal orifice. b. Appendicular orifice. c. It is movable and bound to the lateral abdominal wall.

Abdomen

3 Fig. 16.13: Interior of caecum Table 16.8: Orifices in the caecum Features

Ileocaecal orifice

Appendicular orifice

• Situation

• Present at the junction of caecum and ascending colon

• Situated 2 cm below ileocaecal orifice

• Guarded by

• Valve having upper horizontal and lower concave lip

• A semicircular mucous fold called valve of Gerlach

• Shape

• Slit-like having 2.5 cm transverse diameter

• Small circular opening.

C. Relations a. Peritoneal relations I. It is covered by peritoneum on all sides except posterior surface.

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Exam-Oriented Anatomy

II. It has no mesentery. III. It is movable and bound to the lateral abdominal wall by one or more caecal fold of peritoneum. b. Visceral relations I. Anterior relations i. Coils of the intestine. ii. Anterior abdominal wall. II. Posterior relations i. Appendix in retrocaecal recess. ii. Right psoas and iliacus muscle. iii. Genitofemoral, femoral and lateral cutaneous nerve of thigh. iv. Right gonadal and right external iliac vessels.

Abdomen

3

Fig. 16.14: Posterior relations of the caecum

c. Medial I. Appendix, II. Terminal part of ileum, III. Inferior ileocaecal recess. D. Blood supply a. Arterial supply : Anterior and posterior caecal arteries (branches of ileocaecal artery which are terminal branches of superior mesenteric artery). b. Venous drainage : Ileocaecal vein drains into superior mesenteric vein which drains into portal vein.

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E. Nerve supply : From superior mesenteric plexus a. Sympathetic fibres arise from T10 to L1 segments of spinal cord. b. Parasympathetic fibres arise from vagus nerve. F. Lymphatic drainage : Ileocolic lymph nodes, which drain into superior mesenteric lymph nodes. 2. Applied anatomy ¾ If distended with faeces or gas, the caecum may be palpable through anterior abdominal wall. ¾ The caecum acts as a guideline for localization of obstruction. ƒ If the caecum is distended, the obstruction is in the large intestine. ƒ If the caecum is empty, the obstruction is in the small intestine. ¾ Intussusception: Sometimes terminal part of ileum telescopically invaginates into caecum and ascending colon at ileocaecal junction. This phenomenon is known as intussusception. The tuberculosis of intestine is common at ileocaecal junction. OLA-11 McBurney’s point

1. Site: Junction of medial 2/3rd with lateral 1/3rd of right spinoumbilical line. 2. Structure related: Base of appendix

LAQ-7

Describe appendix under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: It is a narrow tubular diverticulum. It resembles roundworm, hence called vermiform appendix. It arises from posteromedial wall of the caecum. 1. Gross anatomy A. Location: It is situated in the right iliac fossa. It is 2 cm below the intersection of transtubercular (upper part of 5th lumbar vertebra) and right lateral plane. B. Length is 2 to 20 cm (average is 9 cm). Length increases in young adults and diminishes after mid-adult life. C. Peculiarities: Although appendix is the part of large intestine, it is devoid of SAT a. Sacculations, b. Appendices epiploicae, and c. Taenia coli.

3 Abdomen

3. Applied anatomy : It is the area of maximum tenderness in appendicitis.

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Exam-Oriented Anatomy

D. Position of appendix (Fig. 16.15): Position of the appendix is extremely variable. According to the direction of the tip of the appendix, position of appendix is classified as retrocaecal appendix. a. Retrocaecal or retrocolic: The appendix passes behind the caecum and ascending colon. I. It is 12 O’clock position. II. It is most common position of appendix (75%). III. It presents as pain and tenderness at McBurney’s point. IV. Patient experiences pain in extension of hip joint. b. Pelvic appendix I. The appendix is at 4 O’clock position. II. It is 2nd common position of appendix. III. It presents as pain and tenderness at McBurney’s point and hematuria due to pressure of inflamed appendix on the right ureter. IV. In Pelvic Appendix, the patient experiences Pain in Medial Rotation and Flexion and of hip joint. In

Pe App , pain is in MRF.

c. Splenic appendix. I. 2 O’clock position. II. It is rare position of appendix.

Abdomen

3

III. It presents as pain and tenderness at McBurney’s point. IV. It is most dangerous because infection spreads to the general peritoneal cavity.

Fig. 16.15: Common positions of appendix

E. Internal features a. Appendicular orifice b. It is situated on the posteromedial aspect of the caecum 2 cm below the ileocaecal orifice.

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151

c. It is occasionally guarded by semilunar fold of mucous membrane, known as valve of Gerlach.

Fig. 16.16: Less common positions of appendix

F. Relations: Peritoneal relations a. Mesoappendix: It is a small

lar fold of peritoneum suspending appendix.

Abdomen

3

Fig. 16.17: Mesoappendix with appendicular artery

G. Blood supply a. Arterial supply : Appendicular artery, a branch of inferior division of ileocolic artery. It gives a recurrent branch, which anastomoses with the posterior caecal artery. It is an end artery, and hence the tip is least vascular (Fig. 16.18). b. Venous drainage : Appendicular vein drains into superior mesenteric vein which joins with splenic vein and forms the portal vein.

152

Exam-Oriented Anatomy

Fig. 16.18: Arteries supplying appendix

Recall memory—Tip

Abdomen

3

Box 16.2 Note: Examples of end artery I. Appendicular artery II. Central artery of retina III. Cortical arteries of cerebrum H. Nerve supply a. Sympathetic nerves are derived from superior mesenteric plexus. Preganglionic fibres arise from T10 segment of spinal cord. Therefore, the pain is referred to skin over umbilicus which has same segmental innervation. b. Parasympathetic nerve: Vagus. I. Lymphatic drainage : Superior mesenteric lymph nodes via ileocolic nodes. 2. Histology : Appendix has 4 coats. They are described from inside out as A. Mucosa: It has following features a. Simple columnar epithelium with numerous goblet cells. b. Occasional enterochromaffin cells are present. c. Absence of villi. d. Muscularis mucosae and lamina propria are present. e. Lamina propria shows lymphocytes. f. Presence of glands. g. Hiatus muscularis: It is deficient area in muscularis externa. B. Submucosa: It shows lymphatic follicle, which are in ring form.

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153

C. Muscularis externa: It has a. Inner circular muscle. b. Outer longitudinal muscle. D. Serosa is derived from peritoneum and covers the entire tube—except the border where mesoappendix is attached. It is lined by simple squamous epithelium.

Fig. 16.19: Histology of appendix

4. Applied anatomy ¾ Inflammation of appendix is known as appendicitis. It is manifested by Murphy’s triad. ƒ Pain is first felt at umbilical region because appendix and the skin of the umbilicus are supplied by 10th thoracic segment of spinal cord. It is then localized at right iliac fossa due to local peritonitis. It is associated with the tenderness and rigidity at McBurney’s point. ƒ Vomiting. ƒ Temperature because of the infection. ¾ Anatomical factors for appendicitis ƒ Appendix is a blind tube. A faecolith may obstruct the lumen and precipitate the attack of appendicitis.

3 Abdomen

3. Development A. Chronological age: It develops in the early 8th week of intrauterine life. B. Germ layer: Endoderm and mesoderm. C. Source a. Epithelium and glands develop from lower narrow part of caecal diverticulum. It arises from midgut. It is endoderm in origin. b. Remaining coats develop from intraembryonic splanchnic pleuric mesoderm. D. Anomalies a. Subhepatic appendix: It mimics the symptoms of the acute cholecystitis. b. Appendicectomy is difficult in subhepatic appendix.

154

Exam-Oriented Anatomy

ƒ It is supplied by an end artery. ƒ It shows presence of hiatus muscularis. ƒ It shows numerous lymphatic follicles in submucosa. ¾ In retrocaecal appendix, patient experiences pain on extension of right hip joint due to irritation of right psoas major muscle. ¾ In pelvic appendix, patient experiences

Abdomen

3

ƒ Pain in Medial Rotation and Flexion and of hip joint. In Pe App , pain is in MRF. Pain is due to the irritation of obturator internus muscle. ƒ Hematuria is due to pressure of inflamed appendix on right ureter. ¾ During appendicectomy, appendix can be located by tracing taenia coli, which converges at the base of the appendix. ¾ Obstruction of the appendicular artery results into gangrenous appendix. ¾ Ilioinguinal nerve supplies lower most fibres of the internal oblique and transversus abdominis muscle. During split muscle incision of appendix operation, ilioinguinal nerve may be damaged. It reduces the tone of the muscles of anterior abdominal wall (internal oblique and transversus abdominis muscle). It results into direct inguinal hernia. ¾ The damage to the ilioinguinal nerve in the inguinal canal does not paralyse the internal oblique and transversus abdominis muscle because the nerve is purely sensory at this site. ¾ Appendicitis is less likely in extreme ages. This is because of following reasons. ƒ In children, the lumen of the appendix is wide. ƒ In old age, the lumen gets obliterated. ¾ In neglected cases, a long appendix is known to ulcerate into duodenum or perforate into left paracolic gutter.

17 Large Blood Vessels of the Gut

OLA-12 Branches of splenic artery

1. Pancreatic branches. They are many in number. A. Arteria pancreatica magna: This is large branch to the body of pancreas. B. Arteria caudae pancreatis: This is large branch to the tail of pancreas. 2. Short gastric arteries: They are 5 to 7 in number. 3. Left gastroepiploic artery. SN-33

Splenic artery

Introduction: It is the largest artery of coeliac trunk supplying the spleen and pancreas. 1. Origin: It arises from coeliac trunk. 2. Course and relations (Fig. 17.1) A. It courses behind the peritoneum, undulating at upper border of the body of pancreas in a wavy course. B. The crests of its waves appear above the pancreas, the troughs lie hidden behind its upper border. C. It crosses successively the left crus, left psoas muscle, and reaches the hilum of the left kidney. D. From the hilum of the left kidney to the hilum of the spleen, it passes through the lienorenal ligament where it divides into a handful of branches. E. These branches along with veins penetrate the spleen. 3. Peculiarities A. It is interesting to note that spleen is supplied only by splenic artery but splenic artery does not supply only spleen. B. Apart from these structures, splenic artery also supplies blood to a. Fundus part of stomach, b. 1/4th part of greater curvature, and c. Greater omentum. 155

156

Exam-Oriented Anatomy

Fig. 17.1: Relations and course of splenic artery

C. Splenic branches of the splenic artery are end arteries, but the other branches of the splenic artery are not end arteries.

Abdomen

3

D. The branches of splenic artery are segmental in distribution. But tributaries of splenic vein are intersegmental in drainage. 4. Branches: Splenic artery gives numerous (Fig. 17.2) ¾ Pancreatic branches that supply blood to the body and the tail of the pancreas. a. One of the branches of the body of pancreas, a large one, is known as arteria pancreatica magna. It accompanies the main pancreatic duct.

Fig. 17.2: Branches of splenic artery

Large Blood Vessels of the Gut

157

b. Just before its terminal, splenic artery gives rise to the I. Left gastroepiploic artery: It is the largest branch of splenic artery. First it runs between two layers of gastrosplenic ligament and then between two layers of greater omentum. It anastomoses with right gastroepiploic artery which is a branch of gastroduodenal artery. These arteries supply blood to greater omentum but not to transverse colon. II. Short gastric arteries: They are about half a dozen in number and supply the fundus of stomach. 5. Applied anatomy ¾ A posterior gastric ulcer or cancer may erode the splenic artery and cause torrential haemorrhage. ¾ Kehr’s sign: It is occurrence of acute pain in the left shoulder. It is due to presence of blood or other irritant in the peritoneal cavity when the person is lying down and legs are elevated. It is classic sign of rupture of spleen. Interesting about spleen—Tip

Box 17.2 Note: Please do watch animation video of splenic artery (AA5) of 5.24 minutes duration on CBSiCentral App. LAQ-8

Describe inferior mesenteric artery under 1. Origin, 2. Course, 3. Branches, and 4. Applied anatomy.

3 Abdomen

Box 17.1 ¾ Let us now look at some of the interesting and important features of the splenic artery. • One: It is the largest artery of coeliac trunk. The large size of the splenic artery indicates the volume of blood that passes through the capillaries and sinuses of the spleen. • Two: It is one of the most important structures that forms the stomach bed. • And three: It is very tortuous. After understanding important features, let us know the reasons of tortuosity. ƒ One: Tortuosity helps to regulate the blood flow to the spleen in different metabolic activities of life. ƒ Two: It allows free movements of the spleen in respiration without rupture. ƒ Three: It permits distension of the stomach without obstruction to the splenic blood flow.

158

Exam-Oriented Anatomy

Introduction: It is the artery of hindgut. 1. Origin: It arises from front part of the abdominal aorta. It is deep up to the lower border of third part of the duodenum. It is much smaller in diameter than superior mesenteric artery. 2. Course A. It runs obliquely downwards and to the left of the aorta. B. It passes retroperitoneally beneath the peritoneal floor of the left infracolic compartment. C. It crosses the pelvic brim over the sacroiliac joint at the bifurcation of the left common iliac vessels. D. It changes its name to superior rectal artery as the latter crosses the common iliac artery. E. In its course, it lies on the a. Abdominal aorta, and left I. Psoas major muscle, II. Sympathetic trunk, III. Common iliac artery, and b. Hypogastric nerves.

Abdomen

3

Please bear in mind, inferior mesenteric artery in its course lies medial to the left ureter, and does not cross it, although all its branches do. 3. Branches: There are mainly three branches. They are A. Left colic artery: It divides into two branches—the upper and the lower branches. a. Upper branch passes upwards to the splenic flexure. b. The lower branch passes transversely to the descending colon and supplies blood to it. B. Sigmoid arteries: They are three in number. They pass forward between the layers of sigmoid colon and sink into the walls and supply it. The last sigmoid branch anastomoses with the 1st branch of superior rectal artery. C. Superior rectal artery: It is the chief artery of the rectum. It descends up to 3rd sacral vertebra and divides into two branches. About the middle of the rectum, each of these branches divides into smaller vessels. They pierce rectal wall and descend vertically through the submucous coat. At the level of the internal anal sphincter, these branches anastomose with one another to form loops around the lumen. They supply the upper part of rectum. D. Each branch of the superior and inferior mesenteric arteries anastomoses with its adjacent arteries. These anastomotic branches form a continuous vascular arcade along the whole length of the gastrointestinal canal. This is called marginal artery. It begins at the ileocaecal junction. It begins by anastomosing with the ileal branches of the superior mesenteric artery. It ends by anastomosing with the superior rectal artery, branch of inferior mesenteric artery.

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159

Fig. 17.3: Origin, branches and distribution of inferior mesenteric artery

4. Applied anatomy

3 Abdomen

¾ In the event of a block in the inferior mesenteric artery, blood reaches the left side of the colon through the marginal artery. ¾ Occlusion of the aorta or common iliac arteries may also result in dilatation of the marginal and inferior mesenteric arteries. This is an important collateral supply to the legs. The blood reaches via dilated middle rectal vessels arising from the internal iliac artery. ¾ The anastomosis at splenic flexure is between the • Trunk of middle colic artery, and the • Ascending branch of left colic artery. This anastomosis is called arc of Riolan. If by any chance, this anastomosis is not well developed, the arterial supply of the splenic flexure is endangered. Therefore, it is called a critical point which lies at the splenic flexure. ¾ There is anastomosis between the lowest sigmoid branch and the upper rectal branch. The point of origin of the lowest sigmoidal artery is called Sudeck critical point. ¾ The inferior mesenteric artery is ligated proximal to Sudeck’s point to avoid ischaemia and necrosis of the sigmoid colon and rectum. ¾ Occlusion of the inferior mesenteric artery does not always result in ischaemia of the descending and sigmoid colon. This is because of the marginal artery of the colon. ¾ The ischaemia of the descending and sigmoid colon does occur. It is usually maximal in the proximal descending colon because this region is furthest from the collateral anastomosis.

160

Exam-Oriented Anatomy

¾ The ascent of the horseshoe

shaped kidney is arrested at the inferior

mesenteric artery, and results in urinary obstruction. • In carcinoma of the colon, the related paracolic and intermediate lymph nodes are removed only after the ligature of the main branch of the superior or inferior mesenteric artery. • Embolism is uncommon in the inferior mesenteric artery due to better collateral circulation. Beauty of 3 in inferior mesenteric artery Box 17.3

Abdomen

3

It is the artery of the 3rd part of gastrointestinal tract. It is 3 cm long. It supplies left 1/3rd of transverse colon. It arises from abdominal aorta at 3rd lumbar vertebra. It arises 3 cm above the bifurcation of abdominal aorta. It lies behind lower border of 3rd part of duodenum. It extends up to upper 1/3rd of anal canal. It gives 3 branches. The 3rd branch of the inferior mesenteric artery is superior rectal artery. Superior rectal artery extends up to the 3rd sacral vertebra. SN-34

Obturator artery

1. Origin: It arises from anterior division of internal iliac artery. It is close to the origin of the umbilical artery. 2. Course and relations (Fig. 17.4) A. It passes along the lateral wall of the pelvic cavity. B. On its way to the obturator canal, it lies between the parietal pelvic fascia and the peritoneum. C. It passes between the obturator nerve above and its obturator vein below. D. In males , it is crossed by the ureter and the ductus deferens. E. In females

, the ovarian vessels and broad ligament are present on medial side.

F. On entering the obturator canal, the artery does not pierce the parietal pelvic fascia, but passes over its upper border. 3. Branches: They are grouped as branches (Fig. 17.4) A. Inside the pelvis: It gives three branches, namely a. Iliac branches to the iliac fossa, b. Vesical branch to the urinary bladder, and c. Pubic branch to the pubis.

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161

Fig. 17.4: Course and branches of right obturator artery

3 Abdomen

B. Outside the pelvis (in the thigh): The branches are a. Anterior branch to I. Obturator externus, II. Pectineus, III. Adductor longus, IV. Adductor brevis, V. Adductor magnus, and VI. Gracilis. It anastomoses with the posterior branch and the medial circumflex femoral artery. b. Posterior branches form the arterial loop around acetabular circumference. The anastomosis takes place between the obturator externus and the obturator membrane. It supplies the muscles attached to the ischial tuberosity. It anastomoses with the I. Anterior branch, and the II. Inferior gluteal artery. It gives an additional branch called acetabular branch. It enters the hip joint at the acetabular notch. It ramifies in the fat of the acetabular fossa and sends a branch to the ligament of head of femur. It is to be noted that the pubic branch runs over the pubis. It anastomoses with the pubic branch of the inferior epigastric artery with its fellow of the opposite side. Sometimes the anastomosis is large and then the obturator artery appears to be a branch of the inferior epigastric. This is called the abnormal obturator artery (Fig. 17.5).

162

Exam-Oriented Anatomy

Fig. 17.5: Course of abnormal right obturatory artery

4. Applied anatomy : Usually, the abnormal obturator artery passes lateral to the femoral canal. This is safe in the operation of femoral hernia. Sometimes, however, it may lie along the medial margin of the femoral ring, along the free margin of the lacunar ligament. Such an artery is likely to be cut, if an attempt is made to enlarge the femoral ring. OLA-13 Enumerate the branches of coeliac trunk

Abdomen

3

1. Left gastric artery 2. Splenic artery 3. Common hepatic artery SN-35

Enumerate the branches of coeliac trunk

1. Left gastric artery 2. Splenic artery: It gives following branches. A. Left gastroepiploic artery B. Short gastric arteries. 3. Common hepatic artery: It gives following branches. A. Right gastric artery: It passes between two layers of lesser omentum and divides into two branches which anastomoses with two branches of left gastric artery. B. Gastroduodenal artery: It passes behind the 1st part of duodenum and divides into two branches a. The right gastroepiploic artery, b. Superior pancreaticoduodenal artery. C. Cystic artery Box 17.4 Note: Please do watch animation video of coeliac trunk (AA3) of 3.59 minutes duration on CBSiCentral App.

Large Blood Vessels of the Gut

LAQ-9

163

Describe coeliac trunk (coeliac axis, coeliac artery) under following heads 1. Origin, 2. Relations, 3. Branches, and 4. Applied anatomy.

Sandwiching, hugging of coeliac trunk—Tip Box 17.5 • Coeliac trunk is sandwiched between papillary process of liver which is present above and tuber omentale of pancreas from below. • It is hugged by crus of diaphragm from each side. • It is surrounded by the coeliac group of pre-aortic lymph nodes. • Coeliac ganglia of the sympathetic system lie one on each side of it. 3. Branches A. Left gastric artery (Fig. 17.6) a. It is the smallest branch of coeliac trunk and supplies the largest area of stomach.

3 Abdomen

Introduction: It is the artery of the foregut. It supplies part of alimentary canal from cardiac orifice of stomach, to the opening of bile duct, in 2nd part of duodenum. It also supplies the derivatives of foregut, namely liver, spleen and pancreas. 1. Origin: It arises from the front of abdominal aorta. It is present at the level of intervertebral disc of T12 and L1 vertebrae. Its origin is just below the aortic opening of the diaphragm. 2. Relations A. Anterior a. Lesser sac, and b. Lesser omentum. B. Right a. Right crus of diaphragm, b. Right coeliac ganglion, and c. Caudate process of liver. C. Left a. Left crus of diaphragm, b. Left coeliac ganglion, and c. Cardiac end of the stomach. D. Inferior a. Tuber omentale of the pancreas, and b. Splenic vein. E. It is surrounded by coeliac plexus.

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Exam-Oriented Anatomy

b. It runs in opposite direction of the hepatic artery. c. It lies behind the peritoneum and gives an oesophageal branch. d. The oesophageal branch I. Supplies lower end of the oesophagus. II. It runs between two layers of lesser omentum. III. It breaks into two parallel branches, which anastomose with two branches of right gastric artery. It distributes the blood to the lesser curvature of the stomach.

Abdomen

3

Fig. 17.6: Branches of left gastric artery in the folds of lesser omentum

B. Splenic artery a. It is the largest, very tortuous branch of coeliac trunk. b. It lies behind the peritoneum. c. It enters the hilum of the spleen through lienorenal ligament. d. It breaks into 5 to 7 splenic branches. e. It is the main source of arterial supply to pancreas. f. It gives following branches I. Left gastroepiploic artery. It runs on the greater curvature and anastomoses with the right gastroepiploic artery. It supplies blood to the greater curvature of the stomach. II. Short gastric arteries. Practical definition: Those arteries arising at the level of splenic artery are called short gastric arteries. They run upward and supply fundus of the stomach and its greater curvature. C. Common hepatic artery a. It passes over the upper border of pancreas. b. It runs forward at the opening into the lesser sac. c. It reaches porta hepatis and divides into right and left branches to supply left and right halves of the liver. d. It gives following branches.

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I. Right gastric artery i. It passes between two layers of lesser omentum and divides into two branches. Branches of right gastric artery anastomoses with the branches of left gastric artery. ii. It supplies • Pylorus, • Proximal part of duodenum, • Pancreas, and • Nerve supplying stomach. II. Gastroduodenal artery: It passes behind the first part of duodenum and divides into two branches. i. The right gastroepiploic artery • It runs in the greater omentum. • It anastomoses with left gastroepiploic artery. • It gives branches to the anterior and posterior wall of the stomach along greater curvature. ii. Superior pancreaticoduodenal artery • It divides into two branches which encircle the head of pancreas.

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• They anastomose with the inferior pancreaticoduodenal artery, a branch of superior mesenteric artery.

Fig. 17.7: Coeliac trunk and its branches

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4. Applied anatomy ¾ The obstruction of the common hepatic artery proximal to the right gastric artery may save the liver from necrosis. It is due to an establishment of collateral circulation between the gastric and gastroepiploic arteries. ¾ The obstruction at the hepatic artery proper always causes liver necrosis. ¾ Occasionally the coeliac artery is compressed by the median arcuate ligament. This may result in chronic ischaemia of the abdominal viscera. It is associated with postprandial pain and an epigastric bruit. ¾ The site of origin of the coeliac artery is inconsistent. An abnormally high origin above the lower 1/3rd of the 12th thoracic vertebra is frequently associated with the entrapment syndrome. The coeliac artery arises at a higher level in women than in men and the entrapment syndrome is more common in females

.

About coeliac trunk—Tip Box 17.6 The word ‘coeliac’ means ‘related to abdomen’. It is short and wide. It belongs to the category of organs that have more width than length, such as caecum and prostate.

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Box 17.7 Note: Please do watch animation video of coeliac trunk (AA3) of 3.59 minutes duration on CBSiCentral App. SN-36

Left gastric artery

Introduction: It is the 1st branch of coeliac trunk supplying two-thirds part of stomach (Fig. 17.8). 1. Origin: It is the smallest, direct branch of the coeliac trunk (Fig. 17.9).

Fig. 17.8: Distribution of left gastric artery on anterior and posterior surfaces of stomach

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2. Course and relations (Fig. 17.10) A. It runs behind the peritoneum. B. It courses from the upper border of the pancreas across the left crus of the diaphragm to the oesophageal hiatus. C. It forms left gastropancreatic fold. D. It enters at the junction of the two leaves of the lesser omentum. E. It turns to the right along the lesser curvature. F. It breaks into two parallel branches which anastomose with the two branches of the right gastric arteries.

Fig. 17.9: Origin and course of left gastric artery

Fig. 17.10: Relations of nerves and lymph node around left gastric artery

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3. Branches: Left gastric artery gives off branches at right angles. These branches sink into the anterior and posterior walls of the stomach. They anastomose very freely with similar branches from the arteries of the greater curvature. It supplies the largest area of stomach. It provides the major route of blood supply to both surfaces of the stomach (Fig. 17.11). Great things come in small packages—Tip Box 17.8 Thus, two proverbs seem appropriate and befitting to signify its importance: The old Hindi proverb, “Murthy chhoti lekin Kirti moti”, or the English proverb, “Great things come in small packages”. This rightly appeals to left gastric artery. A. It bifurcates into the oesophageal and gastric branches. The oesophageal branches supply lower end of oesophagus and cardiac end of stomach. B. These branches anastomose with the oesophageal branches of thoracic aorta. C. The gastric branches supply anterior and posterior surfaces of upper 2/3rd part of stomach.

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Fig. 17.11: Relations of branches of left gastric artery in oesophageal opening of diaphragm

OLA-14 Branches of superior mesenteric artery

1. Branches from right side A. Inferior pancreaticoduodenal B. Middle colic C. Right colic D. Ileocolic

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2. Branches from left side A. Jejunal, and B. Ileal SN-37

Enumerate the branches and distribution of superior mesenteric artery. Table 17.1: Branches and distribution of superior mesenteric artery

Branches of superior mesenteric artery

Area of distribution

• Inferior pancreaticoduodenal

• Duodenum and pancreas

• Middle colic

• Transverse colon

• Right colic

• Hepatic flexure and ascending colon

• Ileocolic

• Ascending colon, caecum, vermiform appendix and terminal part of ileum

• Jejunal

• Jejunum

• Ileal

• Ileum

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3

Fig. 17.12: Branches of superior mesenteric artery

LAQ-10 Describe superior mesenteric artery under following heads 1. Origin, 2. Course and relations, 3. Branches, and 4. Applied anatomy.

Introduction: It is the artery of midgut supplying all the structures derived from midgut.

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1. Origin: It is the unpaired artery arising from the front of abdominal aorta, 1 cm below the coeliac trunk at the level of 1st lumbar vertebra. Functionally, it is the end artery. Box 17.9 It arises behind the body of pancreas so its origin cannot be seen. It is one of the important structures present at the level of transpyloric plane. Its caliber progressively decreases as successive branches are given off to loops of jejunum and ileum.

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2. Course and relations: Superior mesenteric artery is directed steeply downwards, behind the splenic vein and the body of pancreas. The superior mesenteric vein lies on the right side. It lies superficial to A. Abdominal aorta, B. Left renal vein, C. Uncinate process of the pancreas, and the D. 3rd part of the duodenum. It lies in that order downwards from above. The artery is surrounded by superior mesenteric plexus of nerves. Ref. Fig. 16.3 It passes to the right along the root of the mesentery and ends at the ileum 2’ proximal to the caecum. The artery gives off numerous branches to the gut. 3. Branches: The branches are classified for convenience as A. Branches given from left side: They are about a dozen in number. They pass through the mesentery to reach the gut. The ileal mesentery contains three or more arches, whereas the jejunal mesentery presents 1 or 2 arterial arches. They anastomose with each other to form a series of arches. Straight vessels known as vasa recta arise from the terminal arches and supply the opposite surfaces of jejunum and ileum in alternate manner. The vasa recta are end arteries. The branches are a. Jejunal: They arise from left side, and b. Ileal branches arise from left and anterior aspect of superior mesenteric artery. B. Branches from right side are a. Inferior pancreaticoduodenal, b. Right colic, c. Middle colic, and d. Ileocolic. Ref. Fig. 17.12 Ileal and jejunal arteries—Tip Box 17.10 To be concise and precise. Ileal branches are longer, more numerous and smaller in caliber than the jejunal branches. But the ileal vasa recta are shorter than jejunal vasa recta.

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C. Inferior pancreaticoduodenal artery arises from posterior aspect of superior mesenteric artery at the upper borderr of 3rd part of duodenum. The branch is given before superior mesenteric artery crosses 3rd part of duodenum. It divides into a. Anterior, and b. Posterior branches. I. They run upwards on corresponding aspects of the head of the pancreas. II. They supply the pancreas and duodenum and anastomose with the branches of the superior pancreaticoduodenal arteries. III. Colic branches again are subdivided into branches arising from the highest, middle and lowest part of colon. c. Right colic: The branch given from middle part is right colic artery. It is a small vessel that is highly variable in its anatomy. It runs to the right across all the structures on right side. They are the I. Psoas muscle, II. Gonadal vessels, III. Ureter, IV. Genitofemoral nerve, and the V. Quadratus lumborum muscle. It terminates by dividing into descending and ascending branches that anastomose with the ileocolic and middle colic arteries, respectively. The artery supplies the upper two-thirds of the ascending colon. d. Middle colic: The branch given from the highest part of superior mesenteric artery is middle colic artery. It arises from the anterolateral aspect of the right side of the superior mesenteric artery just below the duodenum. It runs downwards into the transverse mesocolon and divides into I. Right, and II. Left branches. They run along the transverse colon. i. The right branch anastomoses with the ascending branch of the right colic artery. ii. The left branch supplies the transverse colon almost to the splenic flexure. Here it anastomoses with a branch of the left colic artery. e. Ileocolic artery: It is given from the lowest part of superior mesenteric artery. It runs on the posterior abdominal wall a little above the parent vessel. The ileocolic artery gives off various branches to terminal part of the ileum, I. Caecum, II. Appendix III. Lower one-third of the ascending colon. It ends by dividing into i. Superior, and ii. Inferior branches.

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i. The superior branch runs along the left margin of ascending colon and anastomoses with the right colic artery. ii. The inferior branch runs on the ileocolic junction and gives off • Caecal arteries which subdivide into * Anterior caecal artery: It is smaller of the two terminal branches and ramifies over the anterior surface of the caecum. * Posterior caecal artery: It is the largest branch of the ileocolic artery. It supplies the posterior wall of the caecum, as well as the medial and lateral walls of that part of the gut. It gives appendicular branches. • Ileal branches. MCQ—Tip Box 17.11

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1. Practically, appendicilar and ileal branches are end arteries. 2. Note, following arteries have retroperitoneal course A. Inferior pancreaticodoudenal B. Right colic C. Ileocolic 3. Middle colic artery runs in transverse mesocolon. 4. Jejunal and ileal branches traverse the mesentery of small intestine. 4. Applied anatomy ¾ In erect posture, the loops of intestine may come down. This will drag superior mesenteric artery. This compresses left renal vein resulting in varicocele of left renal vein. ¾ Superior mesenteric artery may compress duodenum and give symptoms of chronic duodenal ileus (obstruction to intestine) or superior mesenteric artery syndrome. It is commonly called SMA syndrome or Wilke’s disease. This is suspected in persons who lose weight quickly in a very short time. Symptoms include early satiety, nausea, vomiting, extreme “stabbing” postprandial abdominal pain, abdominal distention, eructation, tenderness of the abdominal area, and severe malnutrition accompanying spontaneous wasting. ¾ Due to the close relation of superior mesenteric artery with pancreas, the infection of pancreas may cause inflammation of the superior mesenteric artery. ¾ Total or segmental infarction may occur due to occlusion of the superior mesenteric artery or one of its distal branches. The occlusion may occur as the result of an embolus, a thrombus, an aortic dissection or an abdominal aneurysm. The more distal the occlusion, the smaller the area of bowel that becomes gangrenous.

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¾ Vascular stenosis may produce intestinal angina with colicky pain referred to the umbilical region. ¾ As the middle colic artery lies to the right of the midline, it leaves a large avascular window to its left in the transverse mesocolon. This is the ideal site for surgical access to the lesser sac and the posterior wall of the stomach. ¾ Terminal 8–10 cm of the ileum need to be excised while dealing with pathology of caecum and descending colon. Failure of resecting this part will result in a vascular necrosis of terminal part of ileum. ¾ The adhesion between transverse mesocolon containing middle colic artery and greater curvature of stomach must be detached with care. ¾ The superior mesenteric artery arises from the abdominal aorta in acute angle. This makes the cannulation of superior mesenteric artery difficult. ¾ The ileocolic artery is the most prominent vessel in the colic mesentery of right lower side. The traction of the caecum in the direction of the anterior superior iliac crest causes the tenting of the mesentery. This allows easy identification of the vessel during laparoscopic surgery. SN-38

Marginal artery

Introduction: It is a single arterial trunk formed by the anastomosis of the colic arteries. 1. Synonymous: Marginal artery of Drummond.

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Fig. 17.13: Marginal artery Note: A. Dark red arteries are main arteries. B. Light red arteries are marginal arteries

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2. Site: It is around the concave margin of the large intestine. 3. Begin: It begins at the ileocaecal junction. 4. Anastomoses with A. Ileal branches of the superior mesenteric artery. B. Superior rectal artery. 5. Applied anatomy : In chronic, progressive occlusion of the superior mesenteric artery, the marginal artery of the colon may become massively dilated. LAQ-11 Describe portal vein under following heads 1. Gross anatomy, 2. Development, and 3. Applied anatomy.

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3

Introduction: The portal system consists of all the veins which carry blood from the abdominal part of the alimentary canal. The exceptions are the lower part of the rectum and the whole of the anal canal. It also drains blood from the pancreas, spleen and gallbladder. From all these viscera, blood is carried to the liver via one channel called the portal vein. The blood of the portal system traverses two sets of capillaries. They are as follows • Capillaries in the wall of the gut and other viscera. • In the liver, it ends in the sinusoids. The blood is collected by central vein and open into hepatic vein which drains into the inferior vena cava. 1. Gross anatomy A. Formation a. Length: 8 cm. b. Formation I. By the union of i. Superior mesenteric vein, and ii. Splenic vein. II. Relation at formation i. Behind the neck of pancreas ii. In front of inferior vena cava iii. At the level of 2nd lumbar vertebra. B. Course and relation (Figs 17.14A to D) a. Course: It runs upward and a little to the right. The course is described in three parts I. 1st part of portal vein runs behind the neck of pancreas, II. 2nd part runs behind the 1st part of the duodenum. III. 3rd part runs in the right free margin of lesser omentum. b. Relations: Relations are described in three parts (Table 17.2).

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Table 17.2: Relations of portal vein Parts

Anterior

Posterior

• Infraduodenal • Retroduodenal

• • • • •

• Inferior vena cava

• Supraduodenal • Within the lesser omentum

• At porta hepatis

Neck of pancreas 1st part of duodenum Common bile duct Gastroduodenal artery Anterior and to the right: – Bile duct. • Anterior and to the left: – Hepatic artery – Hepatic plexus of nerves – Lymphatics • Right and left hepatic ducts • Right and left branches of hepatic artery • Right and left branches of portal vein

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Fig. 17.14A: Schematic diagram of 1st, 2nd and 3rd parts of portal vein

c. Branches I. Right branch i. It is shorter and wider. ii. It enters the right lobe of liver after receiving cystic vein. II. Left branch i. It is longer and narrower than the right.

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B

C

Fig. 17.14B and C: (B) Relations of infraduodenal part of portal vein at AB; (C) Relations of portal vein at retroduodenal part at CD

Fig. 17.14D: Relations of supraduodenal part of portal vein at EF

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ii. It traverses the porta hepatis from its right end to the left end. iii. It gives branches to caudate and quadrate lobes. iv. It receives paraumbilical vein in following ligaments. • Ligamentum teres, and • Ligamentum venosum. Ref. Fig. 15.3 d. Tributaries: It receives following veins (Fig. 17.15) I. At the origin i. Splenic vein, and ii. Superior mesenteric vein. II. From main stem i. Left gastric vein, ii. Right gastric vein, and iii. Superior pancreaticoduodenal vein. III. From the right branch: Cystic vein. IV. From the left branch: Paraumbilical vein. e. Portosystemic anastomosis (Table 17.3) 2. Development (Fig. 17.16) A. Chronological age: It develops in the 2nd and 3rd month of intrauterine life B. Sources a. Infraduodenal part develops from left vitelline vein between I. Joining of splenic vein and superior mesenteric vein, and II. Dorsal intervitelline anastomosis.

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b. Retroduodenal part develops from dorsal anastomosis between I. Right vitelline, and II. Left vitelline veins c. Supraduodenal part develops from right vitelline vein between the I. Cephalic ventral anastomosis, and II. Dorsal anastomosis. d. Right branch: From the part of right vitelline vein cephalic to the ventral anastomosis. e. Left branch: From I. Cephalic ventral anastomosis, and II. Part of the left vitelline vein cephalic to the ventral anastomosis

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3 Fig. 17.16: Developments of portal vein

3. Applied anatomy ¾ Portal pressure • Normal pressure in the portal vein is about 5 to 15 mm Hg. • Earlier it was measured by splenic puncture. • Presently, it is recorded by colour Doppler ultrasonography, a non-invasive method. ¾ Portal hypertension: The causes are grouped as • Presinusoidal ƒ Portal vein thrombosis, ƒ Splenic vein thrombosis, and ƒ Congenital malformation of portal vein

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• Sinusoidal ƒ Cirrhosis of liver (hepatic) ƒ Portal fibrosis • Postsinusoidal ƒ Thrombosis of hepatic vein, ƒ Budd-Chiari syndrome, and ƒ Secondaries. ¾ The effects of portal hypertension are • Congestive splenomegaly, • Ascites, • Collateral circulation through portosystemic anastomosis, and • Varix formation. OLA-15 Enumerate the branches of hepatic artery (hepatic artery proper)

1. Right hepatic artery: It gives cystic artery. 2. Left hepatic artery Hepatic artery proper

1. Definition: The part of the artery beyond the origin of the gastroduodenal artery is often called the hepatic artery proper. 2. Course A. It runs to the right and downwards on the posterior abdominal wall. It reaches the superior part of the duodenum. B. It turns upward to enter the free margin of the lesser omentum. It forms anterior boundary of epiploic foramen. C. It reaches the porta hepatis. D. It divides into right and left branches for the corresponding lobes of the liver. Liver—Tips Box 17.12 Please note, the terminal branches of the hepatic artery are functional end arteries, their anastomosis being insignificant. A. It is important to remember that the caudate and quadrate lobes of the liver, physiologically, belong to left lobe of the liver. B. The quadrate lobe is supplied exclusively by the left hepatic artery while the caudate lobe is supplied by both arteries. C. At times, the right hepatic artery crosses in front of the common hepatic duct, by taking a tortuous course. D. Tortuosity of the right hepatic artery is known as caterpillar turn or Moynihan hump. E. In most cases, the right hepatic artery is sandwiched between the hepatic duct and portal vein. F. It’s good that it doesn’t get pinched off.

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SN-39

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3. Branches: The right hepatic artery gives a branch to the gallbladder called cystic of Calot. It has important anatomical artery. It runs across the cystohepatic variations in its origin and course.

Fig. 17.17: Dangerous and safe ligations of hepatic artery

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3

4. Applied anatomy ¾ The ligation of right and left hepatic artery does not usually lead to infarction of the liver. This is because about 75% of total hepatic blood flow is derived from portal vein and only the remaining 25% comes from the hepatic artery. ¾ It is pertinent to note that the obstruction of the common hepatic artery proximal to the right gastric artery may save the liver from necrosis. This is due to an establishment of collateral circulation between the gastric and gastroepiploic arteries. But when the occlusion affects the hepatic artery proper, the liver necrosis is inevitable, as there is the least chance of development of collateral circulation to the liver. ¾ The cystic artery may be thrombosed in case of cholecystitis but it will not result into gangrene of the gallbladder. This is because of rich blood supply coming from the liver bed. ¾ In gallbladder surgery, 1st cystic artery must be identified and ligated. A word of caution: Ligating right hepatic artery and dividing it may cause profuse haemorrhage and death of the patient. OLA-16 Calot’s

1. Synonymous: Cystohepatic

.

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2. Boundaries (Fig. 17.18): A. The upper border by the liver, B. Left border by common hepatic duct, and C. Inferior border is formed by cystic duct.

Fig. 17.18: Boundaries of Calot’s triangle

3. Applied anatomy

OLA-17 Branches of common hepatic artery

1. Right gastric artery 2. Gastroduodenal artery, and 3. Hepatic artery proper. Ref. Fig.17.19 A and B. SN-40

The common hepatic artery

1. Origin: It arises from coeliac axis. 2. Branches (Fig. 17.19): It divides into A. Right gastric artery, B. Gastroduodenal artery, and C. Hepatic artery proper. A. Right gastric artery runs between the two layers of the lesser omentum and anastomoses with left gastric artery. It supplies blood to the lesser curvature of stomach and the 1st part of duodenum. B. Gastroduodenal artery: It is short but wide artery. It passes down behind the 1st part of duodenum. It descends in front of the neck of pancreas. It remains to the left of the bile duct. At the lower border of the of 1st part of duodenum, it divides into two branches:

3 Abdomen

¾ In gallbladder surgery, a surgeon controls the bleeding of cystic artery. He places the index finger in the epiploic foramen, the thumb anterior to the lesser omentum, and then compresses the hepatic artery. This is called Pringle’s manoeuvre. ¾ This technique is also useful in: • Palpation of gallstones in the bile duct, • Control of haemorrhage due to rupture of cystic artery.

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a. Right gastroepiploic artery: It passes ahead between the 1st part of the duodenum and the pancreas. It turns to the left to enter between the two leaves of the greater omentum and anastomoses with left gastroepiploic artery. It gives off branches at right angles. They are to I. Anterior and posterior walls of the stomach, II. Lower half circumference of the proximal half of the 1st part of duodenum, and III. Greater omentum. b. Superior pancreaticoduodenal artery: It runs along pancreaticoduodenal groove and anastomoses with inferior pancreaticoduodenal artery. The pancreaticoduodenal groove is an extremely vascular region. The duodenum often becomes ischaemic, if separated from the pancreas. I. In addition to these arteries, the II. Supraduodenal artery of Wilkie, and III. Retroduodenal arteries are the branches often arising from the gastroduodenal artery. The supraduodenal branch is an end artery, supplying upper i. Margin, ii. Two-thirds of the anterior surface, and iii. One-third of the posterior surface of proximal half.

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Fig. 17.19A: Course and branches of common hepatic artery

Fig. 17.19B: Course of hepatic artery compared with the bad driven nail in a well

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3. Applied anatomy ¾ The gastroduodenal artery denotes the junction of the • Head with the neck of pancreas, and • Common hepatic artery and hepatic artery proper. ¾ The gastroduodenal artery is clinically important because it is usually invaded by a posterior duodenal ulcer or tumour which results in severe haemorrhage in the peritoneal cavity. Hence, gastroduodenal artery is called artery of duodenal haemorrhage. The condition mentioned above should be suspected and looked into, if the patient complains of pain in the lower lumbar region. ¾ The thrombosis of the supraduodenal artery of Wilkie leads to the Curling’s ulcer in burns which may cause severe bleeding. Box 17.13 Interestingly, anastomotic site between superior and inferior pancreaticoduodenal artery represents the site of junction of the foregut and the midgut at the level of the major duodenal papilla. OLA-18 Enumerate the branches of abdominal aorta.

Fig. 17.20: Paired branches of abdominal aorta

2. Unpaired (Fig. 17.21) A. Coeliac trunk B. Superior mesenteric artery C. Inferior mesenteric artery D. Median sacral artery

3 Abdomen

1. Paired (Fig. 17.20) A. Inferior phrenic artery B. Middle suprarenal artery C. Renal artery D. Gonadal artery E. Common iliac artery

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Fig. 17.21: Unpaired branches of abdominal aorta

Box 17.14 Note: Please do watch animation video of technique to find vertebral level of branches of abdominal aorta (AA29) of 4.00 minutes duration on CBSiCentral App. SN-41

Abdominal aorta

Introduction: Abdominal aorta is the largest artery of abdomen supplying oxygenated blood to the structures in the abdomen and pelvis. It is approximately 10–13 cm long and 2 cm in diameter. It continues as the artery of lower limbs.

Abdomen

3

1. Origin: It is the continuation of descending thoracic aorta at the level of 12th thoracic vertebra. 2. Course and relations A. It passes behind the median arcuate ligament. B. It enters abdomen between the crura of the diaphragm. C. It passes downwards behind the peritoneum. D. It passes in front of the upper 4 lumbar vertebrae. E. It inclines slightly to the left. It leaves sympathetic chain along its left margin. F. Between the origins of the coeliac trunk and the superior mesenteric artery, it is crossed by splenic vein and body of pancreas. These structures form the stomach bed. G. Between the origins of superior and inferior mesenteric arteries, the structures present in front from above downwards are the a. Left renal vein, b. Uncinate process of pancreas, and c. 3rd part of duodenum. 3. Branches: They are grouped as 1st, 2nd and 3rd. A. First group consists of three anterior unpaired branches supplying blood to the viscera. They are a. Coeliac trunk, b. Superior mesenteric artery, and the ventral c. Inferior mesenteric artery (Fig. 17.22).

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Fig. 17.22: Ventral branches of abdominal aorta

B. Second group consists of three lateral paired branches which also supply the viscera. They are a. Suprarenal artery, b. Renal artery, and c. Gonadal artery. C. Third group consists of five lateral paired branches that supply the body wall. They are (Fig. 17.23): a. One inferior phrenic artery, and b. Four lumbar arteries. D. Abdominal aorta trifurcates, i.e. it gives off three branches at the lower border of 4th lumbar vertebra into paired common iliac arteries and unpaired median sacral artery (Fig. 17.24).

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3

Fig. 17.23: Dorsal branches of abdominal aorta

Fig. 17.24: Branches of abdominal aorta

Box 17.15 Note: Please do watch animation video of technique to find vertebral level of branches of abdominal aorta (AA29) of 4.00 minutes duration on CBSiCentral App.

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4. Applied anatomy ¾ Any tumour arising from pancreas or stomach may transmit the pulsations of aorta. These can be mistaken for an aneurysm of abdominal aorta (Fig. 17.25). ¾ The dilatation of artery is called aneurysm. It appears as a pulsatile, palpable, painless abdominal swelling, left of midline.

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Fig. 17.25: Aortic aneurysm

¾ In case of rupture, the blood enters third part of duodenum. The patient vomits blood and also passes black stool or frank blood through the rectum. It is diagnosed by aortography, ultrasound and CT scan. ¾ The narrowing of the abdominal aorta is called coarctation or stenosis. ¾ Abdominal aorta is one of the sites of atheromatous deposits. Atheroma at the bifurcation of the aorta leads to the ischaemia of lower limbs. The patient feels pain while walking. It is called claudication. It may end in gangrene of leg. ¾ The chronic atherosclerosis of the distal segment of abdominal aorta is called Leriche syndrome. It manifests as claudication and pallor. On examination, one does not get the femoral pulsations. ¾ Lack of blood flow into the internal iliac arteries can lead to impotence. SN-42

Inferior phrenic arteries

Introduction: They are the main arteries of the abdominal surface of the diaphragm. They also supply blood to the anterior, posterior and lateral walls of the abdomen. 1. Origin: They are the 1st paired branches of front part of abdominal aorta. 2. Course and relations (Fig. 17.26) A. Each passes upwards and laterally, in front of the corresponding crus of the diaphragm. Each passes along the medial border of the suprarenal gland.

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B. It supplies main mass of the diaphragm arising from the crus. C. The left phrenic artery passes behind the oesophagus and runs forward on the left side of oesophageal opening (Fig. 17.27). D. The right inferior phrenic artery passes behind the inferior vena cava and runs on the right side of caval opening of the diaphragm.

Fig. 17.26: Course and relations of the inferior phrenic artery

Fig. 17.27: Area of stomach supplied by left inferior phrenic artery

3. Branches: Each inferior phrenic artery gives off 2 or 3 small superior suprarenal branches to the suprarenal glands of its own side. Each divides into medial and lateral branch near the posterior border of central tendon of the diaphragm. The medial branch curves forward and anastomoses with the three branches. They are with A. Opposite inferior phrenic artery B. Musculophrenic artery, and C. Pericardiacophrenic arteries. The lateral branch on the right side supplies inferior vena cava and liver, whereas on the left side, supplies to oesophagus, liver and spleen. Box 17.16 Note: Please do watch the animation video of inferior phrenic artery (AA2) of 3.45 minutes duration on CBSiCentral App.

Abdomen

3

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LAQ-12 Describe the abdominal aorta under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Abdomen

3

1. Gross anatomy A. Origin: It is the continuation of thoracic aorta below the diaphragm and behind the median arcuate ligament. B. Termination: It terminates at the lower border of L4 vertebra by dividing into two common iliac arteries. C. Extent: It extends from the lower border of T12 to lower border of L4. D. Course: It descends in front of the bodies of L1 to L4 vertebrae. It lies slightly to the left of midline. E. Relations (Fig. 17.28) a. Anterior I. Vessels i. Coeliac artery ii. Gonadal arteries iii. Superior mesenteric artery iv. Left renal vein v. Splenic vein II. Coeliac plexus III. Body of pancreas IV. Peritoneum i. Parietal peritoneum ii. Root of mesentery b. Posterior: Structures are related to lumbar vertebra. Key structure is lumbar vertebra. I. Left border of L1 to L4 vertebrae II. Intervertebral disc III. Anterior longitudinal ligament IV. Initial part of the lumbar arteries V. 3rd and 4th lumbar veins VI. Left psoas major c. Right I. Cisterna chyli II. Lumbar azygos vein III. Right i. Crus of the diaphragm ii. Coeliac ganglion IV. Inferior vena cava

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A. Tunica intima consists of a. Endothelium lined by simple squamous epithelium. b. Subendothelial connective tissue. It is prominent. B. Tunica media is the thickest coat consists of a. Elastic fibres. b. Internal elastic lamina. It is fenestrated and is formed by elastic fibres. It is indistinguishable from the media. C. Tunica adventitia, a thin-walled outer coat. 3. Development (Fig. 17.29) A. Chronological age: The vascular system appears in the middle of 3rd week. B. Germ layer: Mesoderm. C. Source: The descending aorta is developed from the fusion of two primitive dorsal aortae. The fusion extends from the 4th thoracic to 4th lumbar segments. The median partition disappears and it becomes 1 tube which forms descending thoracic aorta and abdominal aorta. The descending aorta is derived from the a. Left dorsal aorta below the attachment of 4th arch artery, and b. Fused median vessels

Abdomen

3 Fig. 17.29: Development of abdominal aorta

4. Applied anatomy ¾ In thin individuals, the abdominal aorta can be palpated and auscultated. ¾ Pre-renal coarctation (stenosis of the abdominal aorta) leads to reduction of blood to the kidneys. It is more likely to be fatal. ¾ Any tumour arising from pancreas or stomach may transmit the pulsations of aorta. This can be mistaken for an aneurysm of abdominal aorta. ¾ The dilatation of artery is called aneurysm. • Features ƒ It usually results from a congenital or acquired weakness of the arterial wall. ƒ It is common in abdominal aorta. • Sites of aneurysm: Where the branches arise.

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• Clinical manifestations ƒ It appears as a Pulsatile, Palpable, Painless abdominal swelling, left of midline. ƒ The large aneurysm may erode into the adjacent vertebra. ƒ Acute rupture of aneurysm is associated with severe pain in the abdomen or back. ƒ In case of rupture, the blood enters 3rd part of duodenum. ƒ The patient vomits blood and also passes black stool or frank blood through the rectum. • Diagnosis by ƒ Aortography, ƒ Ultrasound, and ƒ CT scan. • Treatment by ƒ Synthetic graft. ƒ Without surgery, 80% cases are likely to die within a year.

¾ Leriche syndrome: It is chronic atherosclerosis of the distal segment of abdominal aorta. • Clinical manifestations ƒ Claudication and pallor ƒ On examination, one does not get the femoral pulsations. ƒ Lack of blood flow into the internal iliac arteries can lead to impotence. • Treatment by suitable surgical techniques. ¾ An operation for removal of the thickened lining of an artery is called endarterectomy. Removal of a thrombus is called thrombectomy. In some cases, segments of the aorta may be replaced or bypassed using synthetic grafts. Box 17.17 Note: Please do watch animation video of introduction of abdominal aorta (AA1) of 9.56 minutes and technique to find vertebral level of branches of abdominal aorta (AA29) of 4.00 minutes duration on CBSiCentral App.

3 Abdomen

¾ Atheromatous deposits: Abdominal aorta is one of the sites of atheromatous deposits. • They make the walls rough and reduce the lumen. • Atheroma at the bifurcation of the aorta leads to the ischaemia of lower limbs. • The patient feels pain while walking. It is called claudication. It may end in gangrene of leg.

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Cartoon of abdominal aorta—Tip Box 17.18

Abdomen

3

Cartoon of abdominal aorta is a study aid to help you understand the branches of abdominal aorta. • Let us depict a cartoon of a standing person having eyebrow, nose, ears, mouth, nipple, 4 hands, umbilicus, legs and a tail. • The person would not look pretty. • However, You will most certainly remember not only this unusual image but also all the branches of the aorta. • So, here’s what we need to do: • Take an A4 size paper. • Divide the paper vertically into two equal halves. • Divide the paper horizontally into three equal parts. • Draw a face in the upper one-third of the paper equidistant from midline. • Draw middle part of the body in the middle one-third of paper. • Draw legs in lower one-third of the paper. • Draw eybrows, each resembling a dome of diaphragm. • Draw a nose in midline resembling the shape of the stomach. • Sketch the mouth, resembling a midgut loop. • Draw small ears. • Trace the upper hands with closed fists resting below the respective ears. • Draw the nipples. • Map out the umbilicus resembling hindgut loop. • Draw 4 fingers of the lower hands placing horizontally on the back. They are between the lumbar vertebrae. • Sketch a tail. • Docs, • Now associate the body parts with various branches of abdominal aorta. • The eyebrows represent inferior phrenic arteries. • The nose defines coeliac trunk. • The mouth represents superior mesenteric artery. • The ears exhibit suprarenal arteries. • The upper hands stand for renal arteries. • The nipples express gonadal arteries. • The “gonadal artery” is the common word used for male

and female

• The male

gonad is testis and the artery for testis is testicular artery.

• The female

gonad is ovary and the artery for ovary is ovarian artery.

gonads.

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193

Contd.

• The umbilicus assumes inferior mesenteric artery. • The 4 fingers on the back represent lumbar arteries. • The legs represent common iliac arteries. • And finally, the tail represents median sacral artery. • Now we are ready with a cartoon of abdominal aorta (Fig. 17.30)

The information in the bracket following label indicates the level of origin of respective artery. 1. Coeliac trunk (between T12 and L1); (2) Suprarenal (between T12 and L1); (3) Renal artery (between L1 and L2); (4) Lumbar arteries arise at the level of the body of respective vertebra; (5) Median sacral at lower border of 4th lumbar vertebra

Box 17.19 Note: Please do watch the animation video of cartoon of abdominal aorta (AA28) of 4.00 minutes duration on CBSiCentral App. SAQ-7

What is the vertebral level of suprarenal, renal, lumbar and median sacral arteries

Table 17.4: Vertebral level of suprarenal, renal, lumbar and median sacral arteries Artery

Part of abdominal aorta between vertebrae

• • • •

• 12th thoracic and 1st lumbar • 1st and 2nd lumbar • 2nd and 3rd lumbar • At the end of 4th lumbar

Suprarenal Renal Lumbar Median sacral

3 Abdomen

Fig. 17.30: Branches of abdominal aorta

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Exam-Oriented Anatomy

Technique to find out the vertebral level of suprarenal, renal, lumbar and median sacral arteries—Tip Box 17.20 Correlate the cartoon of abdominal aorta from front and back to understand the branches of abdominal aorta (Fig. 17.30). For this, We need to recollect the organs for which the arteries are correlating. The ears represent suprarenal arteries. The position of ears is laterally and between eyebrows and mouth. Eyebrows represent inferior phrenic arteries which arise from the abdominal aorta at 12th thoracic vertebra. Mouth represents superior mesenteric artery which arises from the abdominal aorta at 1st lumbar vertebra. Suprarenal arteries arise from that part of abdominal aorta which lie between the 12th thoracic vertebra and 1st lumbar vertebra.

Abdomen

3

The upper limbs represent renal arteries. Upper limbs are positioned between mouth and nipple. Nipples represent gonadal arteries that arise from the abdominal aorta at 2nd lumbar vertebra. Mouth represents 1st lumbar vertebra and nipples represent 2nd lumbar vertebra. Hence, renal arteries arise from that part of abdominal aorta which lies between 1st and 2nd lumbar vertebrae. The dorsal surfaces of 4 fingers are present at 1st, 2nd, 3rd and 4th lumbar vertebrae. The median sacral artery arises from dorsal surface of abdominal aorta. It is at the end part of the abdominal aorta, i.e. at 4th lumbar vertebra. Now try to answer this question: What are the unpaired and ventral branches of abdominal aorta? For this, we need to perform a small trick. We need to slide our fingers on the median plane touching the nose, mouth and umbilicus. The nose represents coeliac trunk. The mouth represents superior mesenteric artery. And finally, the umbilicus represents inferior mesenteric artery.

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Box 17.21 Note: Please do watch the animation video of technique to find level of suprarenal, renal, lumbar and median sacral arteries (AA30) of 4.09 minutes duration on CBSiCentral App. To find the vertebral level of the branches of abdominal aorta—Tip Box 17.22 It is very simple, enjoyable and interesting to find the vertebral level of origin of the branches of the abdominal aorta. Once you grasp the concepts clear and straight. We need to observe three basic rules. 1. We have to begin from the terminal branches of abdominal aorta. 2. We need to follow the “rule of alternate”, “paired-unpaired” and so on. 3. The counting of vertebrae should be from lower vertebra to higher vertebra. To find out the reference point for the terminal branches of abdominal aorta, we need to appreciate the beauty of events occurring at the 4th vertebra of each series.

3 Abdomen

At the 4th cervical vertebra, the common carotid artery bifurcates into internal and external carotid artery. You can easily remember this by remembering “C” for “C” in which the letter “C” refers to Cervical vertebra and Common carotid artery. At the 4th thoracic vertebra, trachea bifurcates. So, to make it easier, just remember “T” for “T” in which the letter “T” refers to Thoracic vertebra as well as Trachea. At the 4th lumbar vertebra, the abdominal aorta bifurcates into right and left common iliac artery. Now take the 4th lumbar vertebra as a reference point and start visualizing the branches of abdominal aorta. Count the vertebrae from the 4th lumbar vertebra. The vertebra of an even number is for paired branches of the abdominal aorta. The vertebra of an odd number is for unpaired branches of the abdominal aorta. The 4th lumbar vertebra: Vertebra with the even number has paired branches, namely common iliac arteries. Contd.

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Contd.

The 3rd lumbar vertebra: Vertebra with odd number has unpaired branch, namely inferior mesenteric artery. The 2nd lumbar vertebra: An even number, has paired branches, namely gonadal arteries. The 1st lumbar vertebra: An odd number, has unpaired branch, namely superior mesenteric artery. The 12th thoracic vertebra: An even number, has paired branches, namely inferior phrenic arteries Box 17.23 Note: Please do watch animation video of technique to find vertebral level of branches of abdominal aorta (AA29) of 4.00 minutes duration on CBSiCentral App. SN-43

Median sacral artery

Introduction: Median sacral artery is the continuation of abdominal aorta. Like the aorta, it clings to the vertebral column (Fig. 17.31).

Abdomen

3

Fig. 17.31: Median sacral artery

1. Comparative anatomy: In lower mammals, it is the anterior caudal artery and supplies the tail. It is very prominent in reptiles like crocodile, turtle, snake, alligator and lizard. It is vestigial in tailless human species. In humans, it supplies muscular part of rectum and other structures. 2. Origin: It is a small, median, unpaired, parietal branch arising from the posterior part of abdominal aorta. It arises just above the bifurcation, i.e. a little above the 4th lumbar vertebra.

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3. Peculiarity: The median sacral artery is part of the posterior abdominal wall. That is to say, no organ, vessel, or nerve intervenes between median sacral artery and the posterior abdominal wall. 4. Course and relations (Fig. 17.32) A. It descends in the midline over the lower two lumbar vertebrae, the sacrum and the coccyx. B. In its course, it is overlapped by the left common iliac vein, superior hypogastric plexus, and rectum, pairs of small arteries that run over the sacrum. C. It provides the spinal branches that enter the pelvic sacral foramina and supply the contents of the sacral canal. D. It may give a small lumbar artery called arteria lumbalis ima. The word ‘ima’ means the lowest. The branches of arteria lumbalis ima are visceral branches and supply the a. Rectum, b. Back of anorectal junction, c. Anococcygeal ligament, and d. Anal canal. It anastomoses with the superior and middle rectal arteries.

Abdomen

3

Fig. 17.32: Relations of median sacral artery

5. Termination: It ends in coccygeal body present in front of coccyx. It contains numerous arteriovenous anastomoses. A. Anterior to the 5th lumbar vertebra, the median sacral artery anastomoses with a lumbar branch of the iliolumbar artery. B. Anterior to the sacrum, it anastomoses with the lateral sacral arteries and sends branches into the anterior sacral foramina. 6. Applied anatomy : It may cause bleeding during the operation of rectum or anal canal, hence should be handled with care.

198

SAQ-8

Exam-Oriented Anatomy

What are the unpaired and ventral branches of abdominal aorta?

Unpaired and ventral branches of abdominal aorta 1. Coeliac trunk 2. Superior mesenteric artery 3. Inferior mesenteric artery Ventral branches of abdominal aorta trick—Tip Box 17.24 What are the unpaired and ventral branches of abdominal aorta? For this, we need to perform a small trick. We need to slide our finger in the median plane touching the nose, mouth and umbilicus. The nose represents coeliac trunk. The mouth represents superior mesenteric artery. And finally, the umbilicus represents inferior mesenteric artery. Box 17.25

Abdomen

3

Note: Please do watch the animation video of technique to find level of suprarenal, renal, lumbar and median sacral arteries (AA30) of 4.09 minutes duration on CBSiCentral App.

18 Extrahepatic Biliary Apparatus

LAQ-13 Describe extrahepatic biliary apparatus under following heads 1. Gross anatomy, 2. Histology of gallbladder, and 3. Applied anatomy.

Introduction: It includes all the structures which are present outside the liver and related to biliary apparatus. 1. Gross anatomy A. Components: It consists of a. Right and left hepatic ducts b. Common hepatic duct c. Gallbladder I. Cystic duct II. Bile duct d. Pancreatic duct e. Hepatopancreatic ampulla f. Major duodenal papilla B. Details of each part a. Cystic duct I. Length: 3 to 4 cm. II. Features i. Mucous membrane of the cystic duct forms a series of 5 to 12 crescentic folds. ii. They are arranged spirally to form the spiral valve of Heister. This is not a true valve. b. Bile duct: It is formed by the union and cystic and common hepatic duct. I. Length is 8 cm. 199

200

Exam-Oriented Anatomy

II. Diameter is 6 mm. III. Course: It runs downward and backward in the free margin of lesser omentum i. It comes in contact with pancreatic duct in the middle of 2nd part of duodenum. ii. The course of the duct in duodenum is oblique. iii. Within the wall, the bile duct and pancreatic duct unite and form hepatopancreatic ampulla. The mucous glands in the bile ducts secrete mucus at much greater pressure than that at which the liver cells can secrete bile. c. Gallbladder I. Features i. Situation: It is situated on the inferior surface of right lobe of liver. ii. Shape: Pear

iii. Dimensions • Length: 7 to 10 cm. • Breadth is 3 cm at the widest part. • Capacity is 30 to 50 ml. II. Parts (Fig. 18.1) i. Fundus: The part of the gallbladder below the inferior border of liver is fundus. ii. Body: It lies in the fossa of the gallbladder of the liver.

Abdomen

3

shaped.

Fig. 18.1: Parts of extrahepatic biliary apparatus

201

Extrahepatic Biliary Apparatus

iii. The infundibulum is the part of the organ between the body and neck. iv. Hartmann’s pouch: It is dilated part of gallbladder present in the posteromedial wall of the neck. v. The gallbladder lies vertically in the angle between the 12th rib and 1st lumbar vertebra. III. Relations (Fig. 18.2) Table 18.1: Relations of the parts of gallbladder Parts

Inferior

Right

• Fundus • Anterior abdominal wall

• Transverse colon

• Rectus • 9th costal abdominis cartilage

• Body • Liver of gallbladder

• Transverse colon and second part of duodenum

• Neck

Superior

• Liver with • 1st part of cystic vessels duodenum

—

—

Left

—

Peritoneum • Entirely surrounded by peritoneum • Superior surface is devoid of peritoneum • Inferior surface is covered by peritoneum

—

Abdomen

3

Fig. 18.2: Relations of gallbladder

i. Relations of the bile duct Table 18.2: Relations of the bile duct Part

Anterior

Posterior

Left

• Duodenal

• Liver

• Inferior vena cava

• Hepatic artery

• Retroduodenal

• 1st part of duodenum • Inferior vena cava

• Gastroduodenal artery

• Infraduodenal

• Head of pancreas

• Gastroduodenal artery

• Inferior vena cava

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Exam-Oriented Anatomy

C. Blood supply: It is divided into a. Arterial supply : The blood supply to the extrahepatic bile ducts is generous. The chief artery is posterior superior pancreaticoduodenal artery. It is assisted by the hepatic and cystic arteries. It is divided into I. Arterial supply of biliary apparatus except lower part of bile duct. i. Cystic artery, branch of hepatic artery, ii. An accessory cystic artery, branch of common hepatic artery, and iii. Artery supplying right hepatic duct. II. Arterial supply of lower part of bile duct: Several branches from superior pancreaticoduodenal artery. b. Venous drainage I. Features i. There is a venous plexus on the wall of the supraduodenal portion of the common duct. It is important guideline to identify the common duct while operating on biliary system. This venous plexus is only visible when the overlying peritoneum has been removed. It does not extend to the cystic duct. ii. The veins of the gallbladder drain into the vein of quadrate lobe of the liver. They open directly or via the pericholedochal plexus. They ultimately enter the hepatic veins. They do not communicate with the portal vessels. II. Venous drainage of biliary apparatus is as follows

Abdomen

3

i. Superior surface of gallbladder drains into hepatic vein, which drains into inferior vena cava. ii. Inferior surface of gallbladder drains into veins of hepatic duct, which drains into inferior vena cava. iii. Lower part of bile duct drains into portal vein. D. Lymphatic drainage a. The lymphatics run in two groups. It is divided into I. Lymphatics of the biliary apparatus except lower part of bile duct drains into cystic lymph nodes. II. Lymphatics of the lower part of bile duct drain into i. Hepatic, and ii. Upper pancreaticosplenic lymph nodes. All these lymphatics ultimately drain into preaortic group of lymph nodes, present in the free margin of lesser omentum. E. Nerve supply : It is divided into a. Part of the biliary apparatus except lower part of bile duct is by cystic plexus, which is formed by I. Right and left vagus, II. Phrenic nerve, and III. Branch from coeliac plexus.

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203

b. Lower part of bile duct has plexus over superior pancreaticoduodenal artery. I. Parasympathetic is i. Motor to • Musculature of gallbladder and • Bile duct, and ii. Inhibitory to the sphincters. II. Sympathetic nerve is vasomotor and inhibitory to sphincter. III. Pain is referred to i. Stomach by vagi, ii. Right scapular region through sympathetic, and iii. Right shoulder through right phrenic nerve. 2. Histology of gallbladder (Fig. 18.3)

3 Abdomen

A. Mucous membrane of the gallbladder is lined by tall columnar epithelium with a striated border. B. Mucosa is highly folded. C. It is characterized by a. No goblet cells, b. No muscularis mucosa, and c. No glands. D. Muscle coat is poorly developed. E. Serosa is lined by simple squamous epithelium.

Fig. 18.3: Histology of gallbladder

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Exam-Oriented Anatomy

3. Applied anatomy ¾ Functions of gallbladder can be investigated by • Ultrasonography, and • Cholecystography ¾ Inflammation of gallbladder is called cholecystitis. This can be diagnosed by the • History of pain in the right hypochondrium. It is associated with tenderness during inspiration at the tip of 9th costal cartilage. This is called Murphy’s sign. ¾ Presence of gallstones in the gallbladder is called cholelithiasis. • The operation for removal of gallbladder is called cholecystectomy. ¾ A subcostal incision gives efficient access to the gallbladder. ¾ Cystogastrocolic band: A fold may stretch from the gallbladder across the duodenum to the greater omentum or transverse colon. It may produce symptoms of partial obstruction. ¾ Infundibulum of the gallbladder is the 1st part usually to contract in case of adhesions of the gut. ¾ Small ducts may connect gallbladder with liver. Usually, these become obliterated. They may persist. For this reason, drainage is mandatory after cholecystectomy (cholecystohepatic duct). ¾ Cancer of the gallbladder is uncommon and have very grave prognosis.

Abdomen

3

19 Spleen, Pancreas and Liver

OLA-19 Enumerate the functions of spleen. Give two causes of its enlargement.

1. Functions A. Phagocytosis: The spleen is an important component of the reticuloendothelial system. B. Haemopoiesis: The spleen is an important haemopoietic organ during fetal life. C. Lymphopoiesis in spleen continues throughout life. D. Storage of RBC E. Immune response: It increases production of lymphocyte in chronic infection. 2. Causes of enlargement A. Liver disease: Cirrhosis, hepatitis B. Acute or chronic infection: HIV, malaria, and tuberculosis C. Blood malignancy: Lymphoma, leukaemia. SN-44

Blood circulation in spleen

1. The spleen is supplied by the splenic artery. It passes through the hilum of the spleen where it divides into 5 or more branches. Within the spleen, these branches divide repeatedly and form the straight vessels called penicilli. The penicilli divide into ellipsoids and arterial capillaries. The course of the blood is controversial (Fig. 19.1). A. Closed theory of splenic circulation: The capillaries are continuous with the venous sinusoids that lie in the red pulp. The sinusoids join together to form veins. B. Open theory of splenic circulation: The capillaries end by opening into the red pulp. In the red pulp, blood enters the sinusoids through their walls. C. Compromise theory, where the circulation is open in distended spleen and closed in contracted spleen. 2. Purpose A. The splenic circulation is adapted for the mechanism of separation and storage of the red blood cells. On the basis of its blood supply, the spleen is said to have 205

206

Exam-Oriented Anatomy

1 Fig. 19.1: Splenic circulation

superior and inferior vascular segments. The two segments are separated by an avascular plane. Each segment may be subdivided into 1 to 2 disc-like middle segments and a cap-like pole segment. LAQ-14 Describe spleen under following heads 1. Gross anatomy,

Abdomen

2. Histology, 3. Development, and 4. Applied anatomy.

1. Gross anatomy A. Location (Fig. 19.2) a. It occupies I. Mainly in the left hypochondrium. II. Partly in the epigastrium. shaped. b. Shape: Wedge c. Dimension: Rule

of odd 1, 3, 5, 7, 9, 11

1” thick. 3” width. 5” length. 7 ounce (1 ounce = 30 g) 7 × 30 = 210 g weight. 9th to 11th ribs are related to the spleen. d. Axis: Oblique, downward, forward and laterally

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207

1

Abdomen

Fig. 19.2: Location of the spleen

B. External features a. 2 ends. I. Anterior end is expanded and reaches mid-axillary line. II. Posterior end is rounded and rests on the upper pole of left kidney. b. 2 surfaces I. Diaphragmatic surface is convex and smooth. II. Visceral surface is concave and irregular. It is occupied by many impressions. i. Gastric impression for the fundus of the stomach. It is the largest. ii. Renal impression for the left kidney. It lies between inferior and intermediate borders. iii. Colic impression for the splenic flexure, and iv. Tail of pancreas. c. 3 borders I. Superior border is characteristically notched near the anterior end. Absence of notch makes one difficult to identify borders, poles and surfaces. II. Inferior border is rounded. III. Intermediate border is also rounded. d. Hilum: It lies on the inferomedial part of gastric impression along the long axis of the spleen. C. Relations (Fig. 19.3) a. Peritoneal relations: Spleen is surrounded by peritoneum and is suspended by following ligaments I. Gastrosplenic ligament, II. Lienorenal ligament, and III. Phrenicocolic ligament. IV. Visceral relations b. Diaphragmatic surface is related to inferior surface of diaphragm. c. Visceral surface is related to i. Fundus of the stomach, ii. Anterior surface of the left kidney, iii. Splenic flexure of the colon, and iv. Tail of the pancreas.

208

Exam-Oriented Anatomy

1

Fig. 19.3: Relations of spleen

D. Blood supply a. Arterial supply

Abdomen

I. Splenic artery is the largest tortuous artery. II. It breaks into 5 to 7 branches. III. It passes through the lienorenal ligament to supply vascular segment of the spleen. b. Venous drainage I. It is drained by splenic vein. II. It is formed at the hilum of the spleen. III. It joins the superior mesenteric vein behind the neck of pancreas and forms the portal vein. E. Nerve supply a. They are derived from coeliac plexus. b. They are mainly sympathetic in nature and are vasomotor in function. c. They also supply smooth muscle present in the capsule. F. Lymphatic drainage a. The splenic tissue has no lymphatics. b. A few lymphatics arise from the connective tissue of the capsule and trabeculae. They drain into the pancreaticosplenic group of lymph nodes, situated along the splenic artery. 2. Histology : The section of the spleen shows (Fig. 19.4) A. Serous coat, which is lined by simple squamous epithelium.

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209

1

Abdomen

B. Fibroelastic coat consists of a. Fibrous coat: It sends trabeculae projecting into the substance of the spleen and branches to form a network. b. Elastic fibres: They are present in the capsule and trabeculae. These fibres bring contraction and relaxation of the spleen. C. Splenic pulp: It is of two types depending upon the type of blood cells. a. Red pulp I. It is scattered throughout the organ. II. It is supported by reticular network. III. It is composed of i. Element of blood, ii. Debris of RBC, iii. Macrophages, and iv. Reticuloendothelial cells. b. White pulp I. These are collection of lymphoid tissue, which are precursors of lymphocytes in the blood. II. The very striking point is an eccentric arteriole, a branch of trabecular artery surrounded by lymphocytes. III. Germinal centre may be seen.

Fig. 19.4: Histology of spleen

210

1

Exam-Oriented Anatomy

3. Development A. Chronological age: It develops in the 5th week of intrauterine life. B. Germ layer: Mesoderm. C. Site: Dorsal mesogastrium near the posterior wall (Fig. 19.5). D. Sources: Spleen is derived from the dorsal mesogastrium, not from the gut tube endoderm. a. Mesenchymal cells, b. Cells of the coelomic epithelium. E. Anomalies a. Abnormal formation: Accessory spleen.

Abdomen

Fig. 19.5: Common locations of accessory spleens

b. Abnormal site I. In the derivatives of the dorsal mesogastrium i. Gastrosplenic ligament, ii. Lienorenal ligaments, iii. Greater omentum. II. In the broad ligament III. In the spermatic cord. c. Spleen develops as splenic lobules, which combine together and form adult spleen. However, the superior border fails to fuse; hence it demonstrates notch on superior border. 4. Applied anatomy ¾ Palpation of the spleen: Normally spleen is not palpable. It is palpable when it is enlarged to about 3 times its normal size. The slightly enlarged spleen can be palpated in the left lateral position. ¾ Splenomegaly: Enlargement of spleen is called splenomegaly. It projects towards the right iliac fossa in the direction of the axis of the 10th rib. ¾ Splenectomy: The surgical removal of the spleen is called splenectomy. ¾ Splenic laceration: The spleen can be lacerated by a fractured rib. The laceration of this vascular organ is a fatal condition. Immediate splenectomy is sometimes indicated.

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211

¾ During splenectomy, tail of the pancreas should be sought first, before putting ligatures to the pedicles of the spleen. SN-45

Relations of liver

1

Abdomen

1. They are divided as peritoneal and visceral. A. Peritoneal relation: Most of the liver is covered by peritoneum except bare areas. There are five bare areas (Fig. 19.6). a. The bare area, b. Groove for inferior vena cava, c. Porta hepatis, d. Fossa for gallbladder, and lar area on the superior surface between two layers of falciform ligaments. e.

Fig. 19.6: Parasagittal secrtion through the liver to show its basic peritoneal relations

B. Visceral relation a. Anterior surface: It is related to I. Xiphoid process, II. Anterior abdominal wall, and III. The diaphragm. lar. It is related to b. Posterior surface: It is I. Vertebral column, II. The diaphragm, III. Right suprarenal gland, IV. Inferior vena cava, and V. Oesophagus.

212

1

Exam-Oriented Anatomy

c. Superior surface: It is quadrilateral and is related to I. Heart, and II. The dome of the diaphragm. d. Inferior surface I. Lesser omentum, II. Impression for gallbladder, III. Right suprarenal gland, IV. Right colic flexure. V. In porta hepatis, the relations are (from posterior to anterior) as follows: Portal vein, Hepatic artery, and Hepatic duct.

VAD

Abdomen

D, DP and DPL. VI. Right lateral surface is related to i. Lower one-third of the diaphragm. ii. Middle one-third pleura and the diaphragm. iii. Upper one-third lung, pleura and the diaphragm.

Fig. 19.7: Peritoneal reflection on the inferior and posterior surfaces of liver

OLA-20 Portal lobule

1. It is based on the direction of flow of bile. 2. It is lar in shape. 3. Note: In portal lobule, parenchyma surrounds the portal triad. 4. It has three central veins at the angle of and portal tract in the centre of 5. The bile from the hepatocytes is collected into bile duct.

.

Spleen, Pancreas and Liver

213

Fig. 19.8: Portal lobule

1

OLA-21 Acinus of liver

Abdomen

1. It is a functional unit of liver. 2. It is diamond shaped. 3. There are A. Two central veins at two opposite ends. B. Two portal triads at other two opposite ends. 4. The acinus is divided into three zones according to the area of distribution of blood supply. A. Zone I: Closed to the blood vessels and well oxygenated. B. Zone II: Slightly away to the blood vessels and less oxygenated. C. Zone III: Away from the blood vessels and poorly oxygenated.

Fig. 19.9: Acinus of liver

SN-46

Bare areas of liver

1. Areas of liver which are not covered by peritoneum are called bare areas. 2. There are five bare areas of liver. A. The bare areas of liver a. It is the largest area. b. It is present on the posterior surface of the right lobe.

214

1

Exam-Oriented Anatomy

c. It is lar and presents following boundaries. lar ligament. d. Apex: Right e. Base: Groove for inferior vena cava. B. Upper and lower limits are formed by superior and inferior layers of coronary ligaments. a. Groove of inferior vena cava b. Groove for porta hepatis c. Fossa for gallbladder d. Groove for ligamentum venosum

Fig. 19.10: The bare areas of liver

Abdomen

SN-47

Lobes of liver

Liver is divided into two lobes: Anatomical and physiological lobes. 1. Anatomical lobes: Liver is divided into anatomical right and left lobes by the attachment of the (Fig. 19.11) • Falciform ligament anteriorly and superiorly; • Fissure for the ligamentum teres inferiorly; • Fissure for the ligamentum venosum posteriorly. A. The right lobe is much larger than the left lobe, and forms 5/6th of the liver. It contributes to all the five surfaces of the liver and presents the caudate and quadrate lobes. a. Caudate lobe is situated on the posterior surface. The boundaries are I. Right side by the groove for the inferior vena cava, on the II. Left side by the fissure for the ligamentum venosum, and III. Inferior side by the porta hepatis. b. Quadrate lobe is situated on the inferior surface and is rectangular in shape. The boundaries are I. Anteriorly by the inferior border, II. Posteriorly by the porta hepatis, III. On the right by the fossa for the gallbladder, and IV. Left by the fissure for the ligamentum teres. B. The left lobe is 1/6th of the liver.

215

Spleen, Pancreas and Liver

1 Fig. 19.11: Liver from below and behind showing anatomical and physiological lobes of liver

2. A vertical line passing through Inferior vena cava and Gallbladder divides Physiological right and left lobes of liver.

IGP

LAQ-15 Describe liver under following heads 1. Gross anatomy, 2. Histology, 4. Applied anatomy.

Introduction: It is the largest mixed gland in the body. 1. Gross anatomy A. Location (Fig. 19.12) a. It is situated in the right upper quadrant of the abdominal cavity. It occupies I. Whole of the right hypochondrium. II. Greater part of epigastrium. III. Left hypochondrium. shaped. b. Shape: Wedge c. Weight: About 1500 g. B. External features: a. 5 surfaces I. Superior II. Inferior, III. Anterior, IV. Posterior, and V. Right lateral.

5 structures. Each structure has 5 items.

Abdomen

3. Development, and

216

Exam-Oriented Anatomy

1

Abdomen

Fig. 19.12: Location of liver

b. 5 borders: They are ill defined except inferior border which is well defined. c. 5 fissures: It is H shaped. Each limb of H indicates structure. I. Fissure for ligamentum teres, II. Fissure for ligamentum venosum, III. Groove for inferior vena cava, IV. Fossa for gallbladder, and V. Porta hepatis. d. 5 lobes I. Anatomical right and left lobes: The liver is divided by a line extending from falciform ligament to the ligamentum teres, which divides into anatomical right and left lobes. II. A vertical line passing through Inferior vena cava and Gallbladder divides Physiological right and left lobes of liver. IGP III. Caudate lobe. IV. Quadrate lobe. V. Riedel’s lobe: Sometimes a tongue-like projection arises from the lower border of liver called as Riedel’s lobe. It extends below the right costal margin. e. 5 peritoneal ligaments I. Falciform ligament. II. Coronary ligament. III. Right

lar ligament.

IV. Left lar ligament. V. Lesser omentum. C. Relations (Fig. 19.13): Refer SN-45 on relations of liver.

Spleen, Pancreas and Liver

217

1 Fig. 19.13: Relations on inferior and posterior surfaces of liver

D. Blood supply I. The oxygenated blood or arterial blood is received by hepatic artery which divides into right and left branches in the porta hepatis. The division is Y shaped in contrast to the T shaped division of portal vein. II. Venous blood is carried to the liver by portal vein which is divided in the porta hepatis into right and left branches which in turn give segmental branches like the arteries. This portal vein carries the products of digestion which are absorbed from the alimentary canal which gets metabolized in the liver. There is no communication between right and left halves of the liver. Even the arteries are end arteries within each half of the liver. Hence, the right lobe shows toxic changes in ingested liver poison. The left lobe shows cirrhotic changes. b. Venous drainage : It is different from the arterial supply, there is mixing of the venous blood of right and left halves of the liver. There are three main hepatic veins that drain into the inferior vena cava. The veins have no extrahepatic course. E. Nerve supply a. Sympathetic fibres arise from the coeliac ganglion. They run with the vessels in the free edge of lesser omentum and enter the porta hepatis. b. Parasympathetic fibres arise from vagus nerve. The above nerves form hepatic plexus in porta hepatis. F. Lymphatic drainage a. Lymphatics of the liver drain into 3 or 4 hepatic nodes in the porta hepatis. They drain downwards along the hepatic artery to the retropyloric nodes and to the coeliac nodes.

Abdomen

a. Arterial supply : The liver receives blood from two sources.

218

Exam-Oriented Anatomy

b. The lymphatics from the bare area drain into extraperitoneal lymphatics which perforate the diaphragm. They drain to the nodes in the posterior mediastinum. 2. Histology (Fig. 19.14)

Abdomen

1

A. The liver is made up of liver cells (hepatocytes) arranged in the form of hexagonal areas called hepatic lobules. B. The lobules are separated by the connective tissue. Each lobule has a central vein and shows numerous sinusoids between the cords of hepatocytes (Fig. 19.15). C. Portal triad: Between the lobules, there are areas filled by connective tissue which contain a. A branch of portal vein, b. A branch of hepatic artery, and c. Interlobular bile duct. D. There are phagocytic cells called Kuffer cells in the walls of sinusoids.

Fig. 19.14: Histology of liver

3. Development A. Chronological age: It develops in the 4th week of intrauterine life. B. Germ layer: Hepatocytes develop from endoderm and remaining structure develops from mesoderm. C. Site: It develops in the ventral mesogastrium and septum transversum. D. Source a. It arises as hepatic bud at the junction of foregut and midgut. b. It develops from an endodermal bud which arises from the ventral aspect of the gut (at the junction of foregut and midgut).

Spleen, Pancreas and Liver

219

1

c. It grows into the ventral mesogastrium and passes through it into the septum transversum. d. The endodermal cells of the hepatic bud give rise to parenchyma of the liver and to bile capillaries. e. The mesoderm of the septum transversum forms the capsule and fibrous tissue of the liver. F. Anomalies (Fig. 19.16): They are rare a. Rudimentary left lobe b. Abnormal lobulation c. Reidel’s lobe d. Absence of quadrate lobe associated with absence of gallbladder e. Accessory lobe in falciform ligament

Fig. 19.16A to E: Anomalies of liver

Abdomen

Fig. 19.15: Hepatic lobule

220

Exam-Oriented Anatomy

4. Applied anatomy

1

¾ The ligation of right and left hepatic artery does not usually lead to infarction of the liver. This is because about 75% of total hepatic blood flow is derived from portal vein. The remaining 25% comes from hepatic artery. ¾ The toxic substances are absorbed from midgut. The vein of midgut is superior mesenteric vein. It opens into right lobe of liver. Hence, right lobe of liver is susceptible for toxic changes. ¾ The choline and methionine are water-soluble compounds. They prevent deposition of fat in liver. They are absorbed throught the midgut. Very little is absorbed through the hindgut. Therefore, left lobe of the liver is not protected in alcoholics. Hence, left lobe of liver is susceptible for cirrhosis. ¾ Amoebic liver abscess is more common in right lobe of liver. ¾ Inflammation of the liver is referred to as hepatitis. ¾ Under certain conditions, liver tissue undergoes fibrosis and shrinks. This is called cirrhosis of the liver. LAQ-16 Describe head of pancreas under following heads 1. Gross anatomy, 2. Histology, 3. Development, and

Abdomen

4. Applied anatomy

Introduction: It is the mixed gland situated in the upper part of left abdomen. 1. Gross anatomy A. Situation: It is situated in the C shaped curvature formed by 1st, 2nd, and 3rd parts of duodenum. B. External features:

1, 2, 3

a. 1 process: Uncinate process. b. 2 surfaces I. Anterior, and II. Posterior. c. 3 borders I. Superior, II. Inferior, and III. Right lateral. C. Relations (Fig. 19.17) a. Peritoneal I. Upper part of the anterior surface is non-peritoneal and related with transverse colon. II. Lower part is covered with peritoneum and is related with coils of jejunum. III. Posterior surface is non-peritoneal.

Spleen, Pancreas and Liver

221

1

Abdomen

b. Visceral I. Uncinate process i. Anteriorly: Superior mesenteric vessels. ii. Posteriorly: Abdominal aorta. II. Surfaces i. Anterior surface • Near the middle: Transverse colon separated by areolar tissue. • Above transverse colon: Overlapped by 1st part of duodenum. • Below transverse colon: Coils of jejunum. ii. Posterior surface • Inferior vena cava. • Bile duct: Runs downwards and to the right, embedded in the substance of pancreas. • Right crus of diaphragm. • Terminal part of renal veins. • Right middle suprarenal artery. • Right sympathetic trunk. • Bodies of L1, L2 vertebrae with intervertebral discs.

Fig. 19.17: Relations of the head of the pancreas as seen in a sagittal section

III. Borders (Fig. 19.18) i. Superior border: • 1st part of duodenum, and • Superior pancreaticoduodenal vessels.

222

Exam-Oriented Anatomy

ii. Inferior border • 3rd part of duodenum, and • Inferior pancreaticoduodenal vessels. iii. Right lateral border • 2nd part of duodenum, • Terminal part of bile duct,

1

• Anastomosis between superior and inferior pancreaticoduodenal vessels, and

Abdomen

• Pancreaticoduodenal lymph nodes.

Fig. 19.18: Relations of borders of head of pancreas with the 1st, 2nd and 3rd, 4th parts of duodenum and supeior mesenteric vessels

Fist and pancreas—Tip Box 19.1 The relations between duodenum and pancreas are best illustrated by Stephan Goldberg through the simile of a fist holding two straws. The hand fist represents the body of pancreas and fingers signify uncinate process. The left straw of the 2 indicates superior mesenteric artery and the right straw signifies superior mesenteric vein. The lower portion of the straw rests on 3rd part of duodenum. The direction of the fist is towards 2nd part of duodenum. D. Blood supply a. Arterial supply I. Superior pancreaticoduodenal artery, is one of the terminal branches of the gastroduodenal artery. II. Inferior pancreaticoduodenal artery, is branch of inferior mesenteric artery (Fig. 19.19).

Spleen, Pancreas and Liver

223

1 Fig. 19.19: Arterial supply of head of pancreas

b. Venous drainage

Abdomen

i. Superior pancreaticoduodenal vein drains directly into portal vein ii. Inferior pancreaticoduodenal vein drains into superior mesenteric vein. It joins with splenic vein and forms portal vein (Fig. 19.20).

Fig. 19.20: Venous drainage of head of pancreas

E. Nerve supply a. Sympathetic nerve: It is derived from coeliac and superior mesenteric plexus. It is vasomotor in function. b. Parasympathetic nerve: It is derived from vagus nerve. It controls pancreatic secretion. F. Lymphatic drainage a. The lymphatics of the upper part of the head drain into coeliac group of lymph nodes. b. The lower part of the head and the uncinate process drains into the superior mesenteric group of pre-aortic lymph nodes (Fig. 19.21).

224

Exam-Oriented Anatomy

1

Fig. 19.21: Lymphatic drainage of head of pancreas

Abdomen

2. Histology : It is lobulated gland, composed of endocrine and exocrine parts (Fig. 19.22). A. The exocrine part shows a. Plenty of serous acini. b. Very few ducts. c. The basal part of the cell of the alveolus is deeply stained and is basophilic. d. The area near the lumen of the cell is stained less heavily and is acidophilic. e. The nuclei are large. B. The endocrine part shows: a. The islets of Langerhans are scattered in the deeply stained pancreatic tissue. b. They vary in size, and diameter. c. They are composed of tightly packed mixture of acidophilic and basophilic small round cells. d. The details of various cells are described in Table 19.1. Table 19.1: Various cells of pancreas Type of cell

% in islets of Langerhans

Secretion

Functions

• Alpha • Beta • Delta

• 20 • 72 • 7

• Glucagon • Insulin • Somatostatin

• Pancreatic polypeptide

• 1

• Pancreatic polypeptide

• Increases blood pressure • Decreases blood glucose • Inhibits secretion of alpha and beta cells • Inhibits exocrine secretion of the pancreas

Spleen, Pancreas and Liver

225

1

3. Development A. Chronological age: It develops in the 4th to 8th week of intrauterine life. B. Germ layer: Endoderm and mesoderm. C. Site: It develops as ventral and dorsal pancreatic bud, at the junction of foregut and midgut. D. Sources a. The ventral pancreatic bud forms I. The main pancreatic duct. II. The uncinate process. III. Lower part of the head of pancreas. b. The dorsal pancreatic bud forms I. Accessory pancreatic duct, and II. The remaining part of head of pancreas not formed by ventral bud. E. Anomalies a. Annular pancreas: Encircles the 2nd part of duodenum (may cause duodenal obstruction). The right part of the ventral bud migrates along the normal route but the left part migrates in an opposite direction. In this manner, the duodenum becomes completely surrounded by pancreatic tissue, and an annular pancreas is formed. b. Accessory pancreatic tissue: It is formed in the walls of the stomach, small intestine, gallbladder or spleen. This is a common finding. c. Inversion of the pancreatic duct: The accessory pancreatic duct is larger than main duct.

Abdomen

Fig. 19.22: Histology of pancreas

226

Exam-Oriented Anatomy

4. Applied anatomy

Abdomen

1

¾ The carcinoma of pancreas is uncommon. However, it commonly occurs in head of pancreas (80%). It obstructs the common bile duct or hepatopancreatic ampulla. It presents as the painless obstructive jaundice. This needs to be compared with painful jaundice of common duct stone. Cancer usually tends to project in one of the three directions. • Between stomach and liver. • Between stomach and transverse colon. • Below transverse colon. ¾ The prognosis is usually poor because of early involvement of portal vein and other structures. ¾ The acute pancreatitis is secondary to complication of mumps. Pain of pancreatic origin is referred to T6–T10 dermatomes. However, involvement of the local parietal peritoneum causes a severe intense pain in the middle of the back.

20 Kidney and Ureter

OLA-22 Name the nerves related to the posterior surface of kidney

There are three nerves related to posterior surface of kidney 1. Iliohypogastric, 2. Ilioinguinal, and 3. Subcostal.

Fig. 20.1: Nerve related to posterior surface of right kidney

OLA-23 Give the relations of posterior surface of left kidney

Posterior surface: Costodiaphragmatic recess of the pleura is the most important relation on the posterior surface of left kidney. Table 20.1: Other structures related on posterior surface of left kidney No. of structures

1

2

3 Nerves

4 Muscles

Left kidney

Lumbar artery

Ribs

• Subcostal • Ilioinguinal • Iliohypogastric

• Psoas major • Transversus abdominis • Quadratus lumborum • The diaphragm

SN-48

Vascular segments of kidney

The renal artery gives five segmental branches, four from its anterior division and one from its posterior division (Fig. 20.2). 227

228

Exam-Oriented Anatomy

Fig. 20.2: The vascular segments of kidney represented by the fingers of right hand

Abdomen

3

1. The segments on anterior aspect are A. Apical, B. Upper, C. Middle, and D. Lower on anterior aspect. 2. On posterior aspect, the segments are A. Posterior B. Apical, and C. Lower segments. SN-49

Psoas major

1. Proximal attachments A. From anterior surface and lower border of all lumbar vertebrae by 5 slips. Each slip arises from a. Lateral surface of bodies of two adjacent vertebrae, and b. Intervertebral disc from T12 to L1 vertebrae. 2. Distal attachments: Tip and medial part of anterior surface of lesser trochanter of femur. 3. Nerve supply : Branches of roots of spinal nerve L2, L3 and L4. 4. Action A. It is a strong flexor of hip joint. It raises the trunk from recumbent to sitting position. B. Maintains the stability of hip joint. C. When acting alone, it brings lateral rotation of the same side. 5. Applied anatomy : Accumulation of pus or blood in the psoas sheath may compress the femoral nerve (Fig. 20.3).

Kidney and Ureter

229

Fig. 20.3: Right side shows normal psoas sheath. Left psoas sheath is distended with pus. It tracks under the inguinal ligament and is seen in the groin

OLA-24 Renal angle

1. Definition: It is the angle between A. Lower margin of 12th rib, and B. Outer border of erector spinae. 2. Posterior relation: Lower part of respective kidney.

¾ Pain arising from kidney is dull aching. ¾ The pain of ureteric calculus begins at renal angle and radiates to the tip of urethra. ¾ The perinephric abscess causes swelling and tenderness at the renal angle. ¾ The kidney is approached by lumbar route. The incision should begin below the renal angle. OLA-25 Floating kidney

1. Following structures support the kidney. A. Fatty capsule B. Fascial capsules C. Renal vessels a. In absence of fatty capsule, weight of the kidney is borne by renal pedicle. It results into falling down the kidney and called floating kidney. 2. The hypermobility of kidney is called floating kidney. The kidney is moved in vertical plane not in horizontal plane. 3. Extreme degree of mobility makes the kidney pedunculated. The pedicle consists of double layer of peritoneum enclosing the renal vessels and nerves and ureters. 4. In operating the floating kidney, one should avoid opening the kidney in peritoneal cavity. One should free the peritoneum before dissecting inward and forward.

Abdomen

3. Applied anatomy

230

Exam-Oriented Anatomy

OLA-26 Pelvic kidney

1. Kidney present in the pelvic region is called pelvic kidney (Fig. 20.4). 2. It is due to failure to ascend in the abdomen. 3. The commonest cause: It is due to fold of peritoneum projecting from lateral pelvic wall. It prevents the ascent of kidney. 4. Complications: Pelvic kidney has A. Abnormal position of ureter, and B. Anomalous blood supply. C. It results into hydronephrosis.

Abdomen

3 Fig. 20.4: Pelvic kidney

SAQ-9

Renal fascia Table 20.2: Renal fascia (Figs 20.5 and 20.6)

Particulars

Anterior

Posterior

• Medially

• Merges with connective tissue around aorta and inferior vena cava

• Fascia covering quadratus lumborum and psoas major • Vertebrae • Intervertebral disc

• Inferiorly

• Extraperitoneal connective tissue

• Fascia iliacus

• Laterally

• Merges with fascia transversalis

• Superiorly

• Fuses and splits to enclose suprarenal gland and continues as diaphragmatic fascia

Kidney and Ureter

231

Abdomen

Fig. 20.5: Horizontal disposition of renal fascia

Fig. 20.6: Vertical disposition of renal fascia

LAQ-17 Describe kidney under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: Kidneys are the paired excretory organs present behind the peritoneum in lumbar region.

232

Exam-Oriented Anatomy

1. Gross anatomy A. Shape: Bean shape. a. Location: Kidneys are present in the epigastric, hypochondriac, lumbar and umbilical regions. b. Extent: They extend from upper border of vertebra T12 to the centre of vertebra L3. Left kidney is slightly higher level than the right kidney. c. Dimension:

1, 2, 3, 4, 5

Thickness: 1” Width: 2” Coverings: 3 Length: 4” Weight: 5 ounces, i.e. 150 g. B. External features: Coverings: There are three coverings (Fig. 20.7). a. Fibrous capsule (true capsule) I. Features i. The fibrous capsule is a thin membrane. ii. It closely invests the kidney. It lines the renal sinus. II. Applied: Normally it can easily be stripped off from the kidney, but in certain diseases, it becomes adherent and cannot be stripped.

Abdomen

3

Fig. 20.7: Coverings of kidney and fate of renal fascia

b. Fatty layer I. Perirenal (perinephric) fat. II. It is formed by adipose tissue. III. It is present outside the fibrous capsule. IV. It is thickest at the borders. c. Fascial layer (false capsule) I. Renal fascia has anterior and posterior layers. II. Anterior layer is called fascia of Toldt.

233

Kidney and Ureter

III. Posterior layer is called fascia of Zukerkandl. IV. Following is the fate of these layers.

Abdomen

Refer Table 20.2: Renal fascia C. Relations of right kidney (Fig. 20.8) a. Peritoneal relations I. Anterior surface is partially covered with peritoneum. II. Posterior surface is entirely non-peritoneal. b. Visceral relations I. Anterior surface is related to i. Right adrenal gland, ii. Liver, iii. Hepatic flexure, iv. 2nd part of duodenum, and v. Jejunum.

Fig. 20.8: Anterior relations of right kidney

Posterior surface: Costodiaphragmatic recess of the pleura is the most important relation on the posterior surface of left kidney. Table 20.3: Other structures related on posterior surface of right and left kidneys No. of structures 1 Right kidney

Left kidney

2

Subcostal Ribs artery

Rib

Subcostal and lumbar arteries

3. Nerves

4. Muscles

• Subcostal • Ilioinguinal • Iliohypogastric

• Psoas major • Quadratus lumborum • Transversus abdominis • The diaphragm

234

Exam-Oriented Anatomy

II. Medial border i. Inferior vena cava, and ii. Ureter. III. Lateral border i. Liver, and ii. Ascending colon. D. Relations of left kidney (Fig. 20.9) a. Peritoneal relations I. Anterior surface is partially covered with peritoneum. II. Posterior surface is entirely non-peritoneal. b. Visceral relations I. Anterior surface i. Adrenal gland, ii. Splenic flexure, iii. Pancreas, iv. Stomach, and v. Jejunum.

Abdomen

3

Fig. 20.9: Anterior relations of left kidney

II. Medial border i. Duodenojejunal flexure, ii. Inferior mesenteric vein, iii. Adrenal gland, and iv. Ureter. III. Lateral border i. Descending colon, ii. Spleen.

Kidney and Ureter

235

E. Blood supply a. Arterial supply : The wide bored renal arteries supply the arterial blood to the kidney at a flow of 1 litre per minute (Fig. 20.10).

Abdomen

I. Renal artery: It is a branch of abdominal aorta which arises at the level of intervertebral disc between L1 and L2. It enters the hilum and divides into i. Anterior trunk which subdivides into four segmental arteries • Apical, • Upper, • Anterior upper, and • Lower. ii. Posterior trunk continues as posterior segmental artery. Segmental artery divides into lobar branches. • Interlobar arteries, • Arcuate arteries, and • Interlobular arteries. There is no collateral circulation between the segmental arteries.

Fig. 20.10: Arterial supply of kidney

II. Sometimes an accessory renal artery arises from the abdominal aorta. It supplies upper or lower pole of the kidney. b. Venous drainage : Veins form the renal segments and communicate with one another unlike the arteries (Fig. 20.11). c. Features of veins I. Small 5 to 6 renal veins unite at the hilum to form a single renal vein. II. Renal veins drain into inferior vena cava. III. Left renal vein is longer than the right renal vein. IV. Left renal vein receives left gonadal and left suprarenal veins.

236

Exam-Oriented Anatomy

Fig. 20.11: Veins of kidneys

F. Nerve supply : By renal plexus. This is formed by

Abdomen

3

a. The sympathetic fibres take origin from last three thoracic and 1st lumbar segments of spinal cord (T10, L1). The sympathetic fibres are vasomotor in function. b. The pain arising due to calculus present in the ureter or renal pelvic passes to the coeliac plexus > splanchnic nerve > sympathetic trunk > spinal cord. The pain is thus referred to the back and the lumbar region and radiate to the anterior abdominal wall and down to the external genitalia. c. Parasympathetic nerves are derived from vagus nerve. The functions are not clearly understood. G.. Lymphatic drainage : The lymphatics of the kidney drain into para-aortic lymph nodes that are present at the level of origin of the renal arteries. 2. Histology : It consists of inner medulla and outer cortex (Fig. 20.12). A. Inner medulla: It presents about 8 to 18 renal pyramids which are striated, pale conical masses. The base of the pyramid is directed to the cortex. The apex projects into the wall of the renal sinus as renal papillae. It contains duct of Bellini, that projects into the minor calyces. Each minor calyx receives 2 or 3 renal papillae. B. Outer cortex: It consists of two portions a. An outer part towards the capsule, and b. Inner part near the medulla. It is called juxtamedullary cortex. The cortex lying between two adjacent pyramids is called renal columns. Cortex over the base of the pyramids is called cortical arch. The cortex consists of I. Light-coloured areas are called the medullary rays, which are formed by the traversing collecting tubules. II. Dark-coloured areas are called convoluted part.

Kidney and Ureter

237

3. Development A. Chronological age: It develops in the 5th week and starts functioning at 9th week of intrauterine life. B. Germ layer: Intermediate mesoderm. C. Site: In the pelvis. D. Source a. Secretory part (nephron and renal corpuscle) develops from metanephric blastema. b. Collecting part (minor calyx, major calyx, pelvis of kidney and ureter) develops from ureteric bud which arises from mesonephric duct. E. Anomalies (Fig. 20.13) a. Depending upon incidence I. Horseshoe kidney: Inferior poles are usually fused (1/500). II. Unilateral agenesis of kidney is relatively common (1/1000). III. Bilateral agenesis (1/3000). IV. Congenital polycystic i. There is a failure of fusion of the collecting and the secreting part. ii. It may be • Autosomal dominant polycystic kidney disease (1/500 to1/1000) or • Autosomal recessive polycystic kidney disease (1/5000).

Abdomen

Fig. 20.12: Histology of kidney

238

Exam-Oriented Anatomy

b. Depending upon the position, shape and rotation. I. Anomalies of position. i. Failure to ascend: The kidney lies in the sacral region. ii. Incomplete ascend: Kidney lies in the region of lower lumbar vertebrae. iii. Over ascend: Kidney lies in the thoracic cavity. II. Anomalies of the shape i. Horseshoe ii. Pancake

kidney: Lower or upper poles may be fused. kidney: The two kidneys form one mass.

iii. Lobulated kidney normally lobulated and this lobulation may persist. III. Abnormal rotation i. Reverse rotation, and ii. Non-rotation of kidney.

Fig. 20.13: Anomalies of the kidney

Abdomen

3

4. Applied anatomy ¾ The angle between lower border of 12th rib and outer border of erector spinae is known as the ‘renal angle’. The tenderness of the kidney is elicited over this angle. ¾ The danger of opening the pleural sac must be kept in mind while exposing the kidney from back. The hypermobile kidney can be moved vertically but not horizontally. Kidney lies in the abundant fat present in the renal fascia. In chronic debilitating patient, the kidney becomes hypermobile and produces symptoms of renal colic. LAQ-18 Describe ureter under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: The ureters are a pair of narrow, thick-walled muscular tubes. They carry urine from kidneys to urinary bladder. 1. Gross anatomy A. Measurements a. Length: 25 cm (10”) of which I. 5” lies in the abdomen, and

239

Kidney and Ureter

Fig. 20.14: The narrowest constrictions of ureter

II. 5” lies in the pelvis. b. Diameter: 3 mm B. Constrictions: Ureter is slightly constricted at 5 places. a. At the pelviureteric junction. b. At the brim of the lesser pelvis. c. Point of crossing of ureter by I. Ductus deferens in male .

d. During its passage through the urinary bladder wall, and e. At its opening in lateral angle of trigone of bladder. C. Course (Fig. 20.15) a. It begins in the renal sinus as a funnel

shaped dilation, called the renal

pelvis. It gradually narrows till the lower end of the kidney and becomes ureter proper. b. The ureter passes downwards and lies medial to the tips of transverse processes of the lumbar vertebrae. c. It crosses the pelvic brim at the sacroiliac joint. d. It passes to the ischial spine and enters the urinary bladder obliquely to open into the trigone of the bladder. D. Relations of ureter a. In abdominal part: This is described as in the I. Renal pelvis: The structures are arranged from anterior to posterior. They are as follows: VAU Renal Vein Renal Artery Ureter most posteriorly.

Abdomen

II. Broad ligament of uterus in female

240

Exam-Oriented Anatomy

Fig. 20.15: Course of ureter in relation to bony landmarks

Abdomen

3

b. Anteriorly and on the right side (Fig. 20.16) I. Peritoneum, II. 3rd part of duodenum, III. Gonadal vessels, IV. Right colic vessels, V. Root of mesentery, and VI. Ileocolic vessels.

Fig. 20.16: Anterior relations of abdominal part of right ureter

Kidney and Ureter

241

c. Anteriorly and on the left side (Fig. 20.17) I. Peritoneum, II. Left colic vessels, III. Gonadal vessels, and IV. Sigmoid colon.

Fig. 20.17: Anterior relations of abdominal part of left ureter

I. Psoas major, II. Tips of the transverse processes, and III. Genitofemoral nerve. e. Medially I. On the right side: Inferior vena cava. II. On the left side i. Left gonadal vein, and ii. Inferior mesenteric vein. f. Relations of ureter in the pelvis I. In its downward course i. Posteriorly • Internal iliac artery, • Anterior trunk of internal iliac artery, • Internal iliac vein, • Lumbosacral trunk, and • Sacroiliac joint.

Abdomen

d. Posteriorly (Fig. 20.18)

242

Exam-Oriented Anatomy

Fig. 20.18: Posterior relations of right abdominal part of right ureter

ii. Laterally: It crosses the following structures ( downwards) Obturator Nerve, Obliterated umbilical Artery, Obturator Artery, Obturator Vein

Abdomen

3

NAAV from above

A word about ovarian fossa Box 20.1 Note: In female

, ureter forms the posterior boundary of ovarian fossa.

II. In its forward course (Fig. 20.19) i. Male • The ductus deferens: It crosses ureter from above and medially. • Seminal vesicle. ii. Female • The broad ligament of uterus. • Uterine artery: It crosses above and in front of the ureter from lateral to medial side. It then passes upwards to enter between the two layers of the broad ligament. • Ureter lies 2 cm lateral to supravaginal part of the cervix. • It lies posterior to vagina (Fig. 20.20).

Kidney and Ureter

243

Abdomen

Fig. 20.19: Relations of right ureter in pelvic part in male

Fig. 20.20: Relations of the pelvic part of ureter in female

III. Intravesical part: It is oblique and acts as a valve. It prevents regurgitation of urine. E. Blood supply a. Arterial supply : It is supplied by the different arteries in three different parts (Fig. 20.21).

244

Exam-Oriented Anatomy

I. Upper part: Receives branches from the i. Renal artery, a branch of abdominal aorta, ii. Gonadal artery, a branch of abdominal aorta, and iii. Colic arteries, branches of superior and inferior mesenteric arteries. II. Middle part i. Branches from the abdominal aorta, ii. Gonadal arteries, and iii. Iliac arteries, terminal branches of abdominal aorta III. Pelvic part i. Vesical arteries, ⎫ ii. Middle rectal, ⎬ branches of internal iliac artery iii. Uterine artery, ⎭ The arteries of the ureter lie close to peritoneum. They divide into ascending and descending branches. They form a plexus on the surface of the ureter and supply it.

Abdomen

3

Fig. 20.21: Arterial supply of right ureter

b. Venous drainage : Veins correspond to the arteries and drain into inferior vena cava. F. Nerve supply : a. The ureter is supplied by sympathetic (T10–L1) and parasympathetic (S2-S4) nerves. They reach the ureter through the renal, aortic and hypogastric plexuses. b. All the nerves appear to be sensory in function. Parasympathetic nerves are motor in function.

Kidney and Ureter

245

2. Histology : It is lined by (Fig. 20.22)

Abdomen

A. Fibrous coat: It is composed mainly of elastic fibres. It is continuous with the capsule of the kidney and adventitia of the urinary bladder. B. Muscle coat a. In upper part of the ureter, I. Outer coat is circular, and II. Inner coat is longitudinal. b. In the lower part of the ureter, I. Outer coat is longitudinal, II. Intermediate is circular, and III. Innermost is longitudinal. C. No submucous coat D. Mucous membrane a. It is lined by transitional epithelium. No distinct basal lamina. The cells of the epithelium rest on a fibrous tissue containing many elastic fibres. The plasma membrane of the surface epithelium is unusual. It encloses special glycoproteins. It is believed that these glycoproteins make the membrane impervious. They prevent the entry of toxic substances present in urine. Thus, they protect adjacent tissue. b. Lamina propria: It is thrown into 6 longitudinal folds when ureter is empty. c. No muscularis mucosa.

Fig. 20.22: Histology of ureter

3. Development A. Chronological age: It develops in the 5th week to 9th week of the intrauterine life. B. Germ layer: Mesoderm.

246

Exam-Oriented Anatomy

C. Source: It is developed from ureteric bud which arises from caudal end of mesonephric duct. The upper part of the ureteric bud forms major and minor calyces of the renal pelvis and lower part forms ureter. D. Site: Para-axial mesoderm E. Anomalies (Fig. 20.23) a. Ureter may be partially or completely duplicated. It is usually associated with duplication of kidney.

Fig. 20.23: Anomalies of ureter

Abdomen

3

b. Abnormal sites of opening of the ureter (Fig. 20.24). The ureter may open in the I. Prostatic urethra, II. Ductus deferens, III. Seminal vesicles, or IV. Rectum.

Fig. 20.24: Abnormal sites of opening of the ureter

Kidney and Ureter

247

c. Upper end of the ureter may be blind. d. Ureter may be dilated (hydro-ureter) because of the obstruction of the urine flow. 4. Applied anatomy

¾ The ureteric stone lodged in the lower part of ureter in female can be felt by per vaginal examination. This is because of close relationship of the ureter to the lateral fornix of vagina. ¾ The abdominal part of ureter receives blood supply from the medial side, therefore, the surgery of ureter of abdominal part is done by approaching from lateral side. ¾ The pelvic part of the ureter receives its blood supply from lateral side, hence the pelvic part of ureter is approached from the medial side.

Abdomen

¾ During hysterectomy or surgical removal of the uterus, the ureter may be injured at the following points. • During ligation of the ovarian vessels in the infundibulopelvic ligament. • At the site of crossing of the uterine artery by the side of the cervix. The left ureter is more likely to be damaged (water under the bridge) due to the close relation with the cervix. ¾ Renal colic: It is the severe pain arising from ureter due to the ureteric stone(s). It causes spasm of the ureter. It starts in the loin and radiates down to the groin, scrotum (or the labia majora), and the inner side of thigh. Because of the common innervation of the ureter and the skin of the above organ, the pain is referred to the above said regions. ¾ The ureteric stone is liable to become impacted at one of the constricted sites.

21 Suprarenal Gland and Chromaffin System

OLA-27 State the two developmental components of adrenal gland?

1. Adrenal cortex develops from mesoderm. 2. Adrenal medulla develops from neural crest cells. OLA-28 What is the structure of adrenal medulla and what are its secretions?

1. Structure of adrenal medulla A. Chromaffin cells a. They are the most abundant cells in the adrenal medulla. b. They are ovoid

shaped secretory cells.

c. They are arranged in clumps or cords. d. They surround the capillaries. e. The cytoplasm of these cells has secretory granules containing catecholamines (adrenaline and noradrenaline). f. The secretory granules stain with stains containing chromium salts (chromaffin reaction). Hence, these cells are called chromaffin cells. g. Chromaffin cells are innervated by preganglionic sympathetic fibres. They correspond functionally to postganglionic sympathetic neurons as both are derived from neural crest cells. B. Ganglion cells a. They are singly or in small groups. b. They are larger in size than chromaffin cells. 2. Secretions: They produce catecholamines (adrenaline and noradrenaline). OLA-29 What is chromaffin reaction?

(Chroma—colour, fil—loving) 1. The cells of adrenal medulla have affinity to colour. Hence, these cells are called chromaffin cells. 248

Suprarenal Gland and Chromaffin System

249

2. The cytoplasm of these cells has secretory granules containing catecholamines (adrenaline and noradrenaline). The secretory granules are stained with chromium salts. This is called chromaffin reaction. The cells are called chromaffin cells. OLA-30 Name the hormones secreted by suprarenal gland.

1. Zona glomerulosa: Mineralocorticoids—aldosterone 2. Zona fasciculate: Hydrocorticoids—hydrocortisone 3. Zona reticularis: Sex hormone—androgen and oestrogen LAQ-19 Describe suprarenal gland under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction A. Shape lar or irregular tetrahedron.

b. Left suprarenal gland is semilunar. B. Dimensions a. Right suprarenal gland is 4 × 4 × 1 cm b. Left suprarenal gland is 5 × 3 × 1 cm C. Weight: 5 g D. Situation a. Right suprarenal gland is situated at upper pole of the right kidney. It covers the anterior surface of right kidney. b. Left suprarenal gland is situated on the upper part of medial border of the left kidney. 1. Gross anatomy A. External features a. Right suprarenal gland has (Fig. 21.1) I. Apex, II. Base, III. Two surfaces i. Anterior and ii. Posterior, and IV. Two borders i. Medial, and ii. Lateral.

3 Abdomen

a. Right suprarenal gland is

250

Exam-Oriented Anatomy

Fig. 21.1: External features of right suprarenal gland

b. Left suprarenal gland has (Fig. 21.2) I. Two ends i. Upper and ii. Lower, II. Two borders i. Medial and ii. Lateral, and III. Two surfaces i. Anterior and ii. Posterior.

Abdomen

3

Fig. 21.2: External features of left suprarenal gland (anterior surface)

c. Hilum of the suprarenal gland I. Right hilum i. Situation: Anterior surface of upper pole of the right kidney ii. Structures leaving • Right suprarenal vein, and • Lymph vessels. II. Left hilum i. Situation: Anterior surface and near the lower pole of the left suprarenal gland.

251

Suprarenal Gland and Chromaffin System

ii. Structures leaving • Left suprarenal vein, and • Lymph vessels Hat ke Box 21.1 Note: Suprarenal arteries do not enter through the hilum of the suprarenal gland. B. Relations (Figs 21.3 and 21.4) a. Right suprarenal gland I. Anterior surface: It has medial and lateral parts i. Medial part: Inferior vena cava (no peritoneum). ii. Lateral part: It is related to liver and is not covered by peritoneum. • The bare area of the liver (no peritoneum). • Inferior surface of the liver (peritoneal).

L for L

3 Abdomen

II. Posterior surface: Divided into lateral and medial parts by crest. i. Lateral part: Anterior surface of the right kidney. ii. Medial part: Right crus of the diaphragm. III. Medial border i. Right inferior phrenic artery, and ii. Right coeliac ganglion.

Fig. 21.3: Relations of anterior surface and medial border of right and left suprarenal glands

b. Left suprarenal gland I. Anterior surface i. Upper part is covered with the peritoneum and related to the posterior surface of stomach. ii. Lower part is non-peritoneal overlapped by the body of pancreas and crossed by tortuous splenic artery.

252

Exam-Oriented Anatomy

II. Posterior surface i. Left kidney, and ii. Left crus of diaphragm. III. Medial border i. Left coeliac ganglion, ii. Left inferior phrenic artery, and iii. Left gastric artery. IV. Lateral border: Left kidney.

Fig. 21.4: Relations of anterior and posterior surfaces of right and left suprarenal glands

Abdomen

3

C. Blood supply a. Arterial supply : It receives blood from following arteries. All arteries enter through peripheral part of gland, i.e. cortex not through the hilum (Fig. 21.5). I. Superior suprarenal artery, a branch of inferior phrenic artery. II. Middle suprarenal artery, a branch of abdominal aorta. III. Inferior suprarenal artery, a branch of renal artery.

Fig. 21.5: Arterial supply of suprarenal gland

b. Venous drainage I. The veins of the suprarenal gland drain in following veins (Fig. 21.6).

Suprarenal Gland and Chromaffin System

253

i. Right suprarenal vein drains inferior vena cava. ii. Left suprarenal vein drains into left renal vein. II. Peculiarities of the veins draining suprarenal gland. i. There is only one thick vein equal to the diameter of lead pencil. The reason to have only one vein is to have the uniform distribution of the hormone to all parts of gland. ii. The vein draining the suprarenal gland leaves through the hilum. iii. Left suprarenal vein is longer as compared to right suprarenal vein.

Fig. 21.6: Venous drainage of suprarenal glands

a. Cortex: Nerve supply of cortex is not known. b. Medulla is supplied by I. Sympathetic (thoracic splanchnic nerve). The pre-ganglionic fibres, directly go to the cells of medulla. II. Phrenic, and III. Vagus nerves Know what is not known—Tip Box 21.2 Note: The exact functions of phrenic and vagus nerves are not known. E. Lymphatic drainage : The lymphatics of the suprarenal glands may accompany any vessel reaching adrenal gland. The lymphatics drain into paraaortic nodes. a. The right para-aortic nodes are situated near the right crus of the diaphragm. b. The left para-aortic nodes are situated near the origin of the left renal artery. 2. Histology : Divided into cortex and medulla. A. Cortex is divided into three zones (Table 21.1)

3 Abdomen

D. Nerve supply

254

Exam-Oriented Anatomy

Table 21.1: Zones of cortex of the suprarenal gland

Abdomen

3

Cortex

Zona glomerulosa

Zona fasciculata

Zona reticularis

• Arrangement of cells in the form of

• Curved columns

• Straight columns

• Branching column

• Hormones secreted

• Mineralocorticoids, e.g. aldosteron

• Glucocorticoids • For example, hydrocortisone

• Sex hormones, e.g. – Androgen – Oestrogen

• Functions

• Promote reabsorption • Participate in car• Reproductive of sodium ions by distal bohydrate, fat and function. convoluted tubules of protein metabolism kidney

B. Adrenal medulla: Cells of medulla exhibit chromaffin reaction, i.e. when treated with potassium dichromate solution, the cytoplasmic granules are oxidized. The medulla turns brown. It shows a. Cords with pheochromocytes (pheo—dusky or brown, chroma—colours, cytes— cell). They are of two types. I. Adrenaline secreting. II. Noradrenaline secreting. b. A few sympathetic ganglion cells show prominent vesicular nucleoli. c. Sinusoidal capillaries present between cell groups. 3. Development (Fig. 21.7) A. Chronological age: Adrenal cortex develops in the 6th week of intrauterine life. B. Germ layer: Inside out a. Cortex develops from mesoderm. b. Medulla develops from ectoderm. C. Site: Between dorsal mesentery and developing gonad. D. Sources: In fetus, the suprarenal is 20 times larger than the adult because of large fetal cortex which regresses after birth. a. Cortex develops from coelomic epithelium. b. Medulla develops from neural crest (neuroectoderm). E. Anomalies a. Abnormal sites I. Deep to the capsule of kidney. II. It may be fused to liver or kidney. b. Congenital adrenal hyperplasia: An abnormal increase in the cells of suprarenal cortex. : It leads to adrenogenital syndrome. It is marked by early I. In male development of secondary sexual characters.

Suprarenal Gland and Chromaffin System

255

Fig. 21.7: Development of suprarenal gland

II. Female

4. Applied anatomy ¾ Addison’s disease: It is caused by atrophy of the suprarenal cortex. It is mainly due to tuberculosis infection. It presents as • Muscular weakness, • Low blood pressure, • Cutaneous pigmentation, and • Change in electrolyte balance. ¾ Pheochromocytoma (pheo—grey, chroma—colour, cyt—cell, oma—tumour): It is a tumour of adrenal medulla, produces paroxysmal hypertension due to secretion of large amount of catecholamine. It produces • Palpitation, • Excessive sweating, • Pallor, • Hypertension, and • Headache of long duration. • Adrenal medulla can be sacrificed and the secretions are replaced by the medicines.

3 Abdomen

i. It causes enlargement of clitoris. Child may be mistaken for pseudohermaphroditism. ii. It produces excessive androgen during the fetal period. It results in masculinization of female.

22 Diaphragm

OLA-31 Structures passing through the aortic opening of the diaphragm.

Descending Thoracic Aorta on left side. Thoracic duct in the middle. Azygos vein on right side.

DTA

OLA-32 Referred pain

It is the area of the skin where pain is felt of the disease of the organ which is away (Fig. 22.1). Table 22.1: Referred pain S. no.

Organ affected

Area of the skin of referred pain

Nerve involved

1

• Appendix

• Umbilicus

• T10 segment of spinal cord

2

• Pelvic appendix

• Medial side of thigh

• Obturator nerve

3

• Ovary and testis

4

• Gallbladder and common bile duct

• Epigastrium • Vagus • Right shoulder • Thoracic segments of • Inferior angle of right scapula spinal cord

5

• Spleen

• Left shoulder (Kehr’s sign) in ruptured spleen • Epigastrium

• Coeliac plexus and right vagus nerve

6

• Diaphragm

• Shoulder tip

• C3, C4 and C5

7

• Peritoneal organs

• Perineum

• S2, S3 and S4

256

257

Diaphragm

Fig. 22.1: Sites of the referred pain

LAQ-20 Describe the diaphragm under following heads 1. Gross anatomy, 2. Openings in the diaphragm, 3. Development, and 4. Applied anatomy.

A. Proximal attachments of diaphragm:

CVS

Costal fibres arise from inner surface of lower 6 costal cartilages and adjacent parts of the ribs. Vertebral fibres arise from upper two lumbar vertebrae by two crura. Sternal fibres arise from posterior surface of the xiphoid process. B. Distal attachments: The muscles insert into trilobed central tendon. C. Relations a. Superiorly I. Pleurae, and II. Pericardium. b. Inferiorly I. Peritoneum, II. Liver, III. Fundus of stomach, IV. Spleen, V. Kidneys, and VI. Suprarenals.

Abdomen

Introduction: It is the musculotendinous partition which separates thoracic cavity from abdominal cavity. It is described as a muscle under origin, insertion, nerve supply and action. 1. Gross anatomy

258

Exam-Oriented Anatomy

D. Actions: The actions of the diaphragm are a. Inspiration: Diaphragm is the principal muscle of the inspiration. b. It acts in all expulsive act, e.g. sneezing, coughing, laughing, crying, vomiting, micturition, defaecation and parturition. c. It acts as a partition between thoracic and abdominal cavity. E. Blood supply a. Arterial supply

IMP

Inferior phrenic artery, 1st branch of the abdominal aorta. Musculophrenic, a terminal branch of the internal thoracic artery. Lower 5 or 6 Posterior intercostal, branches of thoracic aorta. b. Venous drainage I. Inferior phrenic vein drains into inferior vena cava. II. Musculophrenic vein drains into internal thoracic vein. III. Posterior intercostal vein drains into azygos vein. F. Nerve supply : Sensory and motor (Fig. 22.2). a. Sensory: It is divided into

Abdomen

3

I. The sensations of the central part are carried by phrenic nerve (C3, C4 and C5). II. The sensations from the peripheral part are carried by lower intercostal nerves (T6 to T11). b. Motor: Phrenic nerves (C3, C4 and C5)

Fig. 22.2: Nerve supply of diaphragm

2. Opening in the diaphragm (Figs 22.3 and 22.4) A. The major opening in the diaphragm

259

Diaphragm

Opening

Level

Situation

Structures passing

Effect of diaphragmatic contraction

• Carval

• 8th thoracic vertebra

• On the right side of central tendon of diaphragm

• Inferior vena cava • Right phrenic nerve • Lymphatics

• Dilatation of vena caval opening

• Oeso• 10th phageal thoracic vertebra

• The central part of the diaphragm

• Oesophagus • 10th cranial nerve (vagus nerve) and • Oesophageal branch of left gastric artery and accompanying veins

• Constriction of oesophagus

• Relation from left to right descending thoracic aorta, thoracic duct • Azygos vein

• No change

• Aortic

• Lower • Just to the left border of of the midline, 12th thoracic between the vertebra median arcuate ligaments

Fig. 22.3: Situation of openings of diaphragm in sagittal section

Fig. 22.4: Openings in the diaphragm

Abdomen

Table 22.2: Major openings in the diaphragm

260

Exam-Oriented Anatomy

Link memory—Tip Box 22.1 Openings in the diaphragm

Words linked

No. of letters of the words linked

Vertebrae level

Caval

Inferior

8

8th thoracic

Oesophageal

Oesophagus

10

10th thoracic

Aortic

Aortic hiatus

12

12th thoracic

Linking of position of letters in words with position of structures in the opening Keyword

Position of word in the keyword

Position of structure in the aortic opening

Descending

Right

Right

Thoracic

Centre

Centre

Aorta

Left

Left

• Note: All the unpaired red coloured structures, i.e. arteries are on the left side. • All the unpaired blue coloured structures, i.e. veins are on right side. B. The minor openings in the diaphragm are as follows

Abdomen

3

a. The superior epigastric vessels (and some lymphatics) pass between the xiphoid and costal (7th costal cartilage) origin of the diaphragm. This gap is known as Larry’s space or foramen of Morgagni. b. The musculophrenic vessels pierce the diaphragm at the 8th or 9th costal cartilage. c. Several small veins pass through minute apertures in the central tendon. 3. Development (Fig. 22.5) A. Germ layer: It develops from the mesoderm. B. Site: Lateral plate mesoderm. C. Sources a. Septum transversum forms the principal components of the definitive diaphragm. It forms I. Central tendon, II. Anteromedian part, III. Vena caval opening, and IV. Oesophageal opening. b. Pleuroperitoneal membranes: It also forms a major contribution to the development of diaphragm. It gives rise to circumferential part in the ventrolateral region.

Diaphragm

261

Abdomen

c. Dorsal mesentery of the oesophagus forms I. The posterior part of diaphragm between the oesophageal and the aortic openings. II. Crura of the diaphragm d. Left and right body walls. They form tissue on the periphery of the diaphragm. D. Anomalies a. Diaphragmatic hernias: It is one of the common anomalies of the diaphragm. The incidence is 1/2000 newborns. The diaphragmatic hernia may be of following types depending upon the situation. I. Posterolateral, II. Posterior, III. Retrosternal, and IV. Central. b. Accessory diaphragm. c. Congenital eventration (elevation of the dome of diaphragm) of the diaphragm.

Fig. 22.5: Structures forming the development of diaphragm

4. Applied anatomy ¾ Hiatus hernia is relatively common (1%) accounting for 98% of the all diaphragmatic hernia (Fig. 22.6). It is HARD to diagnose. Its manifestations are denoted by each letter of the word HARD” Hiccough Anaemia Regurgitation Dysphagia—difficulty in swallowing.

262

Exam-Oriented Anatomy

Fig. 22.6: Hiatal hernia

¾ The lesion of the phrenic nerve results into the paralysis of the dome of the diaphragm and the affected dome is pushed upwards. ¾ Irritation of the diaphragm may cause referred pain in the shoulder (Fig. 22.7). The phrenic nerve, nerve of diaphragm and supraclavicular nerve supplying the skin of shoulder have same root value.

Abdomen

3

Fig. 22.7: Superficial areas of referred pain of diaphragm

OLA-33 Diaphragmatic hernia

It is protrusion of abdominal contents through the thoracoabdominal diaphragm. It is divided into: Congenital and acquired. 1. Congenital A. Retrosternal: It is through foramen of Morgagni of space of Larry. B. Posterolateral: Commonest type. It is through foramen of Bockdalech. C. Posterior hernia: It is due to failure of development of posterior part of the diaphragm. D. Central: It is rare. E. Hiatal hernia 2. Acquired A. Traumatic B. Hiatal

23 Posterior Abdominal Wall

LAQ-21 Describe renal artery under following heads 1. Origin 2. Course and relations 3. Branches, and 4. Applied anatomy.

Introduction: The renal arteries are the largest arteries of the abdominal aorta supplying kidneys, suprarenal glands and the ureters. They are one of the most important lateral branches. The renal arteries take about 20% of the cardiac output, which is approximately 1.2 litres/minute. They supply organs that represent 1/100th of the total body weight. 1. Origin: They are direct branches of abdominal aorta; hence, they are high pressure arteries. They arise at right angle between L1 and L2 vertebrae. They lie below the origin of superior mesenteric artery and above the origin of gonadal arteries (Fig. 23.1).

Fig. 23.1: Origin of renal artery

2. Course and relations (Figs 23.2 and 23.3): Relations at the hilum of kidney are VAU , i.e. renal Vein, renal Artery and pelvis of Ureter from the front backward. A. The left renal artery is little shorter and little lower than the right. It passes behind the a. Left renal vein, 263

264

Exam-Oriented Anatomy

b. Body of the pancreas, and c. Splenic vein. B. It may be crossed anteriorly by the inferior mesenteric vein. C. It crosses the a. Left crus of diaphragm, b. Left psoas major muscle and runs behind the left renal vein. D. The renal vessels are covered by splenic vessels and the tail of pancreas. The right renal artery is longer, and little lower, than the left renal artery. It is bedded by the right crus of diaphragm and right psoas major muscle. It is blanketed by the inferior vena cava and short renal vein. E. The blankets, i.e. inferior vena cava and short renal vein are covered by the head of pancreas, bile duct and 2nd part of duodenum.

Abdomen

3 Fig. 23.2: Relations of right and left renal arteries Note: Right renal artery is longer than the left renal artery

Fig. 23.3: Relations of accessory renal artery on right side

3. Branches (Fig. 23.4) A. Within the renal sinus, the renal arteries divide further into primary branches. They give rise to an anterior and a posterior division.

Posterior Abdominal Wall

265

Fig. 23.4: Branches of renal artery supplying the segments of kidney

Fig. 23.5: Branches of renal artery to ureter and suprarenal gland

3 Abdomen

B. The anterior division gives branches that supply the apical, the upper, middle and lower segments. The posterior division supplies posterior segment. Each of them supplies a specific region of renal tissue, there being no anastomoses between arteries to adjoining regions. These primary branches are called segmental arteries. C. The kidney can be divided into five segments on the basis of their distribution. Segmental arteries are the end arteries and supply renal vascular segments. The anterior division passes in front of the renal pelvis. D. They are distributed to different segments or areas of the kidney. E. Lobar arteries arise from each segmental artery. F. Before entering the renal substance, each lobar artery gives off 2 or 3 interlobar arteries. G. The interlobar arteries run toward the cortex on each side of the renal pyramid. H. At the junction of the cortex and the medulla, the interlobar arteries give off the arcuate arteries, which arch over the bases of the pyramids. I. The arcuate arteries give off several interlobular arteries that ascend in the cortex. The afferent glomerular arterioles arise as branches of the interlobular arteries. J. Other branches of renal artery: Each renal artery gives off (Fig. 23.5) a. Suprarenal branch to the suprarenal gland, and

266

Exam-Oriented Anatomy

b. Ureteric branch to the upper end of ureter. c. 1 or 2 accessory renal arteries arise frequently from the aorta, above or below the main artery. 4. Applied anatomy ¾ The aberrant renal artery is usually due to failure to regress one of the arteies as the kidney ascends. The aberrant artery entering the lower pole may cause compression of pelviureteric junction producing hydronephrosis. Sometimes, the aberrant artery is the sole supply of one vascular segment of the kidney. ¾ Ligature of a segmental or of an aberrant artery will cause ischaemia and death of the corresponding segment of the kidney. ¾ Sometimes an extra or ectopic renal artery may compress the superior end of the ureter, causing obstruction of urinary flow. • As renal arteries are end arteries, the surgeon will 1st compress the anomalous artery before tying it. This is to assess whether such ligation will excessively impair circulation to the kidney. If so, an artificial arterial bypass graft may be attempted. • Renal artery stenosis causes ischaemia of the kidney which releases renin and cause hypertension.

Abdomen

3

¾ For transplantation, the renal artery is anastomosed to the internal or external iliac artery and the renal vein to the external iliac vein. ¾ The amount of blood circulating through the renal cortex is about 4 or 5 times more than that of the medulla. But the blood flow may be reversed in crushing injuries due to the vasoconstriction of the interlobular arteries at the junction of the outer two-thirds and inner one-third of the cortex. SN-50

Middle suprarenal artery

Introduction: It is a small artery of suprarenal gland. 1. Origin: The paired suprarenal arteries arise from abdominal aorta, between paired inferior phrenic and paired renal arteries at the level of the superior mesenteric artery (Fig. 23.6). 2. Course and relations (Fig. 23.6) A. They run laterally across the crura of diaphragm to enter the suprarenal glands. Here they anastomose with the suprarenal branches of the phrenic and renal arteries. B. The right middle suprarenal artery passes behind the inferior vena cava, near the right coeliac ganglion. Here it lies between the right crus of diaphragm and the inferior vena cava. C. Right middle suprarenal artery is frequently multiple. D. The left middle suprarenal artery passes close to the left coeliac ganglion, splenic artery and the superior border of the pancreas. E. It lies behind the posterior wall of lesser sac.

Posterior Abdominal Wall

267

Fig. 23.6: Origin, course and relations of middle suprarenal artery

3. Applied anatomy ¾ Bilateral adrenalectomy was sometimes performed in certain inoperable mammary or prostatic cancer patients. ¾ The right suprarenal gland is more difficult to explore because of its close proximity to the liver and its retro-vena caval position. It is difficult to ligate right middle suprarenal artery as it courses behind the vena cava.

SN-51

Testicular artery

Introduction: Testicular arteries, as the name suggests, supply the testes. They are one of the most important of the lateral branches. 1. Origin: They are long and slender arteries, arising from the abdominal aorta just below the renal arteries and well above the inferior mesenteric artery. 2. Courses and relations (Fig. 23.7A and B) A. They have a long intra-abdominal course. B. They course retroperitoneally. C. They descend obliquely downwards and laterally. D. They run lateral to the inferior epigastric vessels, traverse the deep inguinal canal and passes as one of the structures of spermatic cord. E. Testicular arteries do not enter the pelvis. F. Within the cord, testicular arteries lie anterior to the ductus deferens. They reach the posterosuperior aspect of the testes and divide into a. Medial, and b. Lateral branch on the respective surfaces.

3 Abdomen

Box 23.1 Note: Please do watch animation video of middle suprarenal artery (AA10) of 3.12 minutes duration on CBSiCentral App.

268

Exam-Oriented Anatomy

Fig. 23.7A: Anterior relations of testicular artery

Abdomen

3

Fig. 23.7B: Posterior relations of testicular artery

269

Posterior Abdominal Wall

G. They pass through the tunica albuginea and ramify in the tunica vasculosa. Terminal branches enter the testis over the surface. Some pass into the mediastinum testis and loop back before reaching their distribution. H. In the abdomen, the testicular artery supplies a. Perirenal fat, b. Ureter, and c. Iliac lymph nodes. I. In inguinal canal, they supply cremaster. J. In epididymis, they anastomose with the artery to the vas, a branch of inferior vesical artery. Table 23.1: Relations of testicular artery

Relations

Right

Left 3rd part of duodenum

Anterior

Left colic vessels Inferior mesenteric vein Descending colon

Root of mesentery Terminal part of ileum

Posterior

Psoas major Ureter Genitofemoral nerve Inferior vena cava

¾ Torsion of the testis is a rotation of the testis and the spermatic cord within the scrotum. • Bell-clapper deformity is a predisposing factor in testicular torsion. ƒ In this condition, the tunica vaginalis joins high on the spermatic cord. ƒ It leaves the testis free to rotate.

¾ Torsion commonly occurs in active young men and children and is accompanied by severe pain. If not treated quickly, the testicular artery may be occluded. It is followed by necrosis of the testis. ¾ Occlusion of the testicular artery within the abdomen usually does not affect blood supply to the organ. ¾ Interruption of the artery in the inguinal or scrotal region causes infarction of testis because of involvement of both testicular arteries.

3 Abdomen

3. Applied anatomy

270

Exam-Oriented Anatomy

¾ Compression of testicular vessels leads to ischaemic necrosis of the testis. In about 80% of cases, failure to diagnose and intervene immediately can result in the loss of testis. ¾ During the later decades of life, some of the scrotal vessels are seen to supply the testes; as a result, the spermatic cord may usually be divided without causing necrosis of testis. ¾ In the region of the epididymis, there is an anastomosis between the testicular artery and the artery to the vas. The artery to the vas is too small to sustain the testis, if the testicular artery is divided. ¾ Treatment of varicocele is ligation of the veins of pampiniform plexus above the inguinal ligament at the neck of scrotum. ¾ If testicular artery is tied close to the testis, it will be completely devoid of the arterial supply. There is communication between testicular artery and artery to vas and cremaster. If the tie is away from the testis, then it will receive blood from artery of vas and cremaster. SN-52

Abdomen

3

Ovarian artery

Introduction: Ovarian arteries, as the name suggests, supply the ovaries. They are one of the most important of the lateral branches. 1. Origin: They are long and slender arteries, arising from the abdominal aorta just below the renal arteries and well above the inferior mesenteric artery. 2. Courses and relations (Fig. 23.8A and B) A. They have a long intra-abdominal course. B. They course retroperitoneally. C. They descend obliquely downwards and laterally. D. The structures lying posterior to ovarian artery on both sides are a. Psoas major muscle, b. Ureter, and c. Genitofemoral nerve of the respective sides. E. In addition to these structures, inferior vena cava is the most important posterior structure of the right ovarian artery. However, anterior relations of right and left testicular arteries are different. F. The anterior structures of right ovarian artery are a. 3rd part of duodenum, b. Branches of the inferior mesenteric artery, c. Root of mesentery, and d. Terminal ileum. G. The anterior structures of left ovarian artery are a. Left colic artery, b. Inferior mesenteric vein, and c. Lower part of the descending colon.

Posterior Abdominal Wall

271

Fig. 23.8A: Anterior relations of ovarian artery

Abdomen

3

Fig. 23.8B: Posterior relations of ovarian artery

3. Course of ovarian artery in the pelvis. A. The ovarian artery crosses the external iliac vessels at pelvic brim. B. The artery turns medially in the suspensory ligament of ovary. C. It splits into a branch to the a. Mesovarium that supplies the ovary, and b. Broad ligament of uterus that supplies the tube. D. On each side, a branch passes lateral to the uterus to anastomose with the uterine artery.

272

Exam-Oriented Anatomy

E. Other branches of the ovarian artery accompany the round ligaments. F. They pass through the inguinal canal to the skin of the labium majus and the inguinal region. 4. Applied Anatomy ¾ Ovarian pain is referred to the skin of the umbilicus. The pain fibres of ovary and skin of umbilicus have the same segmental nerve supply. ¾ The ureter and the ovarian vessels lie in close proximity to one another in ovarian fossa. During salpingectomy or saplingo-oophorectomy, there are chances of ligating the ureter during ligation of ovarian artery. SN-53

Lumbar arteries

Introduction: The lumbar arteries are intersegmental arteries that supply the body wall and are in series with the posterior intercostal and subcostal arteries. Occasionally, the 5th pair of lumbar arteries arise from the median sacral artery or is represented by the lumbar branches of the iliolumbar arteries. 1. Origin: They are four paired, slender branches arising from posterolateral part of abdominal aorta. They lie opposite the central part of the bodies of upper 4 lumbar vertebrae (Fig. 23.9).

Abdomen

3 Fig. 23.9: Origin of lumbar arteries

2. Course and relations A. The course of the lumbar arteries is variable. They hug and stay close to the bodies of lumbar vertebrae. They lie between lumbar vertebrae. B. They pass beneath the lumbar sympathetic trunks and the fibrous arches of the psoas. These structures protect lumbar arteries. C. On the right side, the inferior vena cava overlies the lumbar arteries. D. The following arteries hide behind the respective crus of diaphragm. a. Upper two lumbar arteries on right side, and b. Upper 1st on left side E. They continue into the muscles of the posterior abdominal wall. They lie posterior to lumbar plexus.

Posterior Abdominal Wall

273

F. On reaching the quadratus lumborum, upper three lumbar arteries pass behind the muscle. G. At the lateral border of quadratus lumborum, they pierce the aponeurosis of transversus abdominis, and run forward between transversus abdominis and internal oblique. H. The 4th lumbar artery lies in front of the quadratus lumborum. I. It passes across to the neurovascular plane along the upper margin of the iliolumbar ligament.

Fig. 23.10: Course, relations and branches of lumbar artery

3 Abdomen

3. Branches: Each lumbar artery has a dorsal branch. It passes backward between the adjacent transverse vertebral processes. This branch also has a spinal branch. It enters the vertebral canal. 4. Distribution and termination A. Each lumbar artery supplies the a. Dorsal muscles of the back, b. Joints, and c. Skin of the back. B. The spinal branch of the 1st lumbar artery supplies the terminal part of the spinal cord proper. C. The 2nd, 3rd, 4th lumbar arteries supply the a. Cauda equina, b. Meninges, and c. Vertebral canal. 5. Anastomosis A. The lumbar arteries end by anastomosing with a. Lower intercostal, b. Subcostal, c. Iliolumbar, d. Deep circumflex iliac arteries, and e. Inferior epigastric artery. B. Spinal branches anastomose with the arteries above, below and across the midline.

274

Exam-Oriented Anatomy

6. Applied anatomy ¾ Occlusion of all or most of lumbar arteries is by aneurysm of the abdominal aorta. It may cause ischaemia of the cauda equina, producing the so-called ‘cauda equina syndrome’. ¾ 1st, 2nd and 3rd lumbar arteries pass behind the quadratus and might be encountered in approaching a kidney from behind. SN–54

Abdomen

3

Common iliac arteries

Introduction: They are arteries of lower parts of anterior abdominal wall, pelvis and lower limb. They are asymmetrical. 1. Origin: They are the two terminal branches arising from the abdominal aorta opposite the centre of the body of the 4th lumbar vertebra. They are a finger’s breadth to the left of the middle line. Left common iliac artery is short. It is 4 cm long. However, right common iliac artery is 5 cm long. 2. Course and relations A. Each common iliac artery at once diverges from the other and runs laterally downward. B. The relations can be grouped as (Fig. 23.11) a. Anterior, b. Posterior, c. Lateral, and d. Medial. a. Anterior relations of the common iliac artery are covered anteriorly by peritoneum that separates them from the coils of small intestine. I. Please note that ureters are the important anterior relations on the respective side of common iliac artery. They cross at the bifurcation of common iliac artery. II. The other structures on anterior surface of both common iliac arteries are i. One-half of the aortic sympathetic plexus, ii. Coils of intestine, iii. Hypogastric nerves, and iv. Lumbar splanchnic nerves. III. It may be noted here that superior mesenteric vessels which continue as superior rectal vessels, and the apex of sigmoid mesocolon are structures related only to the left common iliac artery. b. Posterior relations: Each artery rests upon the lower 1/2 of the body of the 4th and the whole of the 5th lumbar vertebra, as well as the disc above and below the latter, and the ganglionated sympathetic trunk. The right common iliac artery has three posterior veins: They are left and right common iliac veins and the inferior vena cava. However, the left common iliac artery has

Posterior Abdominal Wall

275

only left common iliac vein as posterior relation. Lying deeply behind each artery in the lumbosacral are the obturator nerve, lumbosacral trunk, and between them lies the iliolumbar artery. c. Lateral relations are from above downwards. I. Inferior vena cava, II. Right common iliac vein, III. Psoas major, and IV. Genitofemoral nerve. d. Medial relations are from below upwards, I. Right common iliac vein, II. Left common iliac vein, and III. Hypogastric sympathetic plexus.

Abdomen

3

Fig. 23.11: Relations of common iliac artery

3. Branches: Each common iliac artery terminates by dividing into the larger external and smaller internal iliac arteries. The division occurs at the level of L5 and S1 and in front of sacroiliac joint. It also gives small branches to the A. Peritoneum, B. Psoas major, C. Ureter, D. Adjacent nerves, and E. Surrounding areolar tissue.

276

Exam-Oriented Anatomy

4. Applied anatomy ¾ Among all the structures, a surgeon needs to remember that ureters cross the common iliac artery from the front. This piece of information helps the surgeon identify the ureter during the operation. ¾ Pressure of right common iliac artery may bring partial obstruction to venous flow of left common iliac vein. It results in varicosity of left leg. We know that varicosity usually is a bilateral condition. Hence, varicosity of left leg points the diagnosis of varicosity due to pressure of right common iliac artery. ¾ In case of ligation of common iliac artery, blood supply to the lower limb of the respective side is maintained by anastomosis between superior and inferior epigastric artery. OLA-34 External iliac artery

Abdomen

3

1. It is one of the two terminal branches of common iliac artery, given at sacroiliac joint. It continues as a femoral artery at mid-inguinal point deep into inguinal ligament. 2. Peculiarities. A. Descending colon ends and sigmoid colon begins in front of the left external iliac artery at the level of pelvic brim. B. The inferior epigastric artery, branch of external iliac artery, is usually a significantly larger artery; it provides dominant blood supply to rectus abdominis. C. It forms an important pathway for collateral circulation between vessels above and vessels below the diaphragm. 3. Termination: External iliac artery continues as femoral artery distal to inguinal ligament. SN-55

Relations of external iliac artery

1. Anterior relations (Figs 23.12 and 23.13) A. The artery is covered by the parietal peritoneum and extraperitoneal areolar tissue. B. The right external iliac artery at its commencement is crossed by the terminal part of the ileum, and sometimes by the vermiform appendix. C. The left external iliac artery at its commencement is crossed by the pelvic colon. D. The left limb of mesocolon of inverted V is attached along the upper half of the left external iliac artery. E. Each external iliac artery may be crossed by the ureter, if it does not cross bifurcation of the common iliac artery. F. Both arteries are crossed superiorly by the ovarian vessels in females testicular vessels in males

and

.

G. The ‘vas deferens’ in males and round ligament of uterus in females arch over external iliac artery from lateral to medial aspects. H. Above the inguinal ligament, external iliac artery is crossed by genital branch of

Posterior Abdominal Wall

277

Fig. 23.12: Relations of external iliac artery in male

Abdomen

3

Fig. 23.13: Relations of external iliac artery in female

278

Exam-Oriented Anatomy

the genitofemoral nerve. I. It is to be noted here that genitofemoral nerve and the femoral branch of genitofemoral nerve run along the lateral side of the external iliac artery. Near the inguinal ligament, each vessel is crossed by deep circumflex iliac vein. J. The external iliac lymph nodes lie along the artery. 2. Posterior relations A. The artery rests upon the iliac fascia at the pelvic brim, except for a little way above the inguinal ligament, where it lies upon the psoas muscle. B. The right external iliac artery, at the commencement, has its external iliac vein behind it at a short distance. SN-56

Abdomen

3

Branches of external iliac arteries

It gives two branches 1. Inferior epigastric artery, and 2. Deep circumflex iliac arteries. Both are intimately related to the anterior abdominal wall. 1. Inferior epigastric artery A. Origin: It is one of the two collateral branches of external iliac artery. B. Course and relations a. It lies medial to the deep inguinal ring and ascends medially upwards. b. Here it is hooked laterally by the ductus deferens in males and round ligament of uterus in females

.

c. It crosses arcuate line, which is curved and sharp like a sickle and can injure itself. d. It pierces the transversalis fascia and enters rectus sheath. e. It anastomoses with the superior epigastric artery. C. Branches: They are grouped inside and outside the rectus sheath (Fig. 23.14). a. The branches inside the sheath are I. Muscular supplying rectus abdominis, and II. Cutaneous supplying skin over the muscle. b. The branches outside the sheath are I. Cremasteric branch, and II. Pubic branch. I. Cremasteric branch enters through the deep inguinal ring and supplies and round ligament of the coverings of the spermatic cord in males uterus in females

.

II. Pubic branch anastomoses with the pubic branch of the obturator artery. When the pubic branch of inferior epigastric artery is large, it is called abnormal obturator artery.

Posterior Abdominal Wall

279

Fig. 23.14: Branches of external iliac artery

3. Applied anatomy ¾ The abnormal obturator artery is often called “artery of death” by surgeons. During the operation for strangulated femoral hernia, it may be injured while cutting the lacunar ligament. ¾ Inferior epigastric artery is a guide to identify the deep inguinal ring. ¾ Inguinal hernia, medial to inferior epigastric artery, is direct inguinal hernia and lateral to it is indirect inguinal hernia. ¾ The external iliac artery is intimately related to deep inguinal ring and may be damaged in the extensive medial dissection of the deep inguinal ring particularly during hernial repair. This is very much true when the operation is performed in preperitoneal plane. ¾ Disease of the right external iliac artery results in adhesion with the corresponding vein. ¾ The walls of the vessels may get fused, making the dissection hazardous. ¾ Rupture of the inferior epigastric artery occurs during a forceful bout of cough, a strong muscular contraction and a blow on the anterior abdominal wall in

3 Abdomen

2. Deep circumflex iliac artery A. Origin: It is a lateral branch of the two terminal branches of the external iliac artery. B. Course and relations: It runs above the inguinal ligament, almost in the opposite direction. a. It runs laterally and upwards along the back of inguinal ligament towards the anterior superior iliac spine. b. It pierces the fascia transversalis, and continues along the iliac crest, up to its middle where it pierces the transversus abdominis. c. It enters the interval between the transversus and the internal oblique muscles. d. It supplies the muscles of lower abdomen. e. At the anterior superior iliac spine, it anastomoses with the superior gluteal, the lateral circumflex femoral and superficial circumflex iliac arteries. f. Just behind the anterior superior iliac spine, it gives off an ascending branch which runs upwards in the neurovascular plane.

280

Exam-Oriented Anatomy

pregnant women. It forms a tense painful swelling at the lateral border of the rectus abdominis muscle (rectus sheath haematoma). ¾ It is important to remember that bleeding from the inferior epigastric artery can be disastrous as large quantity of blood gets collected in the closed space. ¾ The incision at McBurney’s point for appendicitis is likely to damage the ascending branch of the deep circumflex iliac artery. SN-57

Superior vesical artery

Introduction: Superior vesical artery is the first large branch of the anterior trunk of internal iliac artery. 1. Origin: It arises as the 1st large branch of the anterior trunk of internal iliac artery. It is at the level of the upper border of the pubis. 2. Development: It is the persistent, proximal, patent part of the fetal umbilical artery. 3. Course and relations A. It lies on the lateral wall of the pelvis just below the pelvic brim. B. It runs anteroinferiorly medial to the posterior surface of the pubis. C. The artery is crossed by the ductus deferens.

Abdomen

3

Fig. 23.15: Origin, course, relations and branches of superior vesical artery

4. Distribution A. It supplies to the upper portion of the bladder. B. It anastomoses with the vesical branch of the a. Obturator, b. Prostatic, and the c. Inferior vesical of the same side, and d. Superior vesical of the opposite side.

Posterior Abdominal Wall

281

5. Branches A. Urachal to the medial umbilical ligament, and B. Ureteric to the lower end of the ureter. It also supplies to the seminal vesicles. 6. Fate: The distal part of superior vesical artery becomes obliterated to form medial umbilical ligament (Fig. 23.16).

Fig. 23.16: Medial umbilical fold containing medial umbilical ligament

Name that betrays—Tip Box 23.2 Medial umbilical ligament does not function as ligaments.

SN-58

Lateral sacral artery

1. Origin: Lateral sacral arteries are the branches of posterior division of internal iliac artery (Fig. 23.17). They are usually two in number: A. Superior, and B. Inferior.

Fig. 23.17: Origin of lateral sacral artery

3 Abdomen

7. Applied anatomy : Damage to the medial umbilical ligament below the level of the apex of the bladder should be avoided. It may cause gangrene of the bladder.

282

Exam-Oriented Anatomy

2. Course and relations (Fig. 23.18) A. They course downwards and medially to the front of the lateral mass of the sacrum. B. They pass in front of the pyriformis and sacral nerves. C. Both arteries lie upon the sacrum lateral to the anterior sacral foramina. D. The superior is confined to the region of the 1st two foramina. E. The inferior descends lateral to the sympathetic trunk as low as the coccyx.

Abdomen

3

Fig. 23.18: Course, branches and relations of lateral sacral artery

3. Anastomosis: They anastomose with the median sacral artery. 4. Distribution: They are distributed to the pyriformis and sacral nerves. 5. Branches (Fig.23.18) A. They give spinal branches. They enter the anterior sacral foramina and reach the sacral canal to supply its contents. B. Before entering the sacral canal, each spinal branch gives off a posterior branch. C. It emerges through the posterior sacral foramen. D. It anastomoses with branches of the superior and inferior gluteal and internal pudendal arteries. E. The lateral sacral arteries anastomose with each other and with the median sacral artery. OLA-35 Tributaries of inferior vena cava

Tributaries of inferior vena cava. Refer Fig. 23.20 1. Common iliac vein 2. 3rd and 4th lumbar veins 3. Right A. Gonadal vein B. Renal vein C. Suprarenal vein

Posterior Abdominal Wall

283

4. Hepatic veins are three large and many small veins directly open into inferior vena cava. LAQ-22 Describe inferior vena cava under following heads 1. Gross anatomy, 2. Development, and 3. Applied anatomy.

Introduction: It is the systemic vein draining the venous blood from the structures present below the diaphragm.

3 Abdomen

1. Gross anatomy A. Formation: It is formed by the union of a. Right common iliac vein. b. Left common iliac vein. B. Level of formation: It is formed on the right side of body of 5th lumbar vertebra. C. Termination: It opens into the lower and posterior part of right atrium and guarded by valves. D. Dimensions a. Breadth: 1" b. Length: 9" E. Relations (Fig. 23.19) a. Anterior: From above downward, it is related to I. Posterior surface of liver II. Epiploic foramen III. 1st part of duodenum IV. Portal vein V. Head of pancreas VI. 3rd part of duodenum VII. Right gonadal artery VIII. Parietal peritoneum IX. Root of mesentery X. Right common iliac arteries. b. Posterior I. Lower part i. Bodies of lumbar vertebrae ii. Anterior longitudinal ligament iii. Right • Psoas major muscle • Sympathetic trunk iv. 3rd and 4th lumbar arteries

284

Exam-Oriented Anatomy

II. Upper part i. Right • Crus of the diaphragm • Coeliac ganglion • Renal artery ii. Part of suprarenal gland iii. Middle suprarenal artery iv. Inferior phrenic artery c. Right side I. Right ureter, II. 2nd part of duodenum, III. Medial border of right kidney, IV. Hepatorenal pouch of Morison, and V. The bare area of the liver. d. Left side I. Abdominal aorta, II. Right crus of the diaphragm, III. Cisterna chyli, IV. Thoracic duct, V. Omental bursa and VI. Caudate lobe of liver.

Abdomen

3

Fig. 23.19: Relations of inferior vena cava

Posterior Abdominal Wall

285

F. Tributaries: The tributaries of vena cava are not identical with the branches of the abdominal aorta. Particularly, there is no corresponding to the three ventral branches to the gut. Following are the tributaries of the inferior vena cava (Fig. 23.20). a. Pair of veins I. Common iliac II. Renal III. Phrenic IV. Lumbar veins. 3rd and 4th pair of lumbar veins drain directly into the inferior vena cava. b. Unpaired veins I. Right gonadal vein. II. Right suprarenal vein and hepatic veins. Odd to remember—Tip Box 23.3 Note: 1st and 2nd lumbar veins drain into ascending lumbar vein.

Abdomen

3

Fig. 23.20: Tributaries of inferior vena cava

286

Exam-Oriented Anatomy

2. Development (Fig. 23.21) A. Chronological age: It develops in the 8th week of intrauterine life. B. Germ layer: Mesoderm. C. Sources: It is a composite vessel. It is developed from the following sources from below upwards. “a” From the persistent caudal part of right posterior cardinal vein (between its junction with the supracardinal and anastomosis between the two posterior cardinals). “b” From the lower part of right supracardinal vein (between its junction with the posterior cardinal and supracardinal subcardinal anastomosis). This part receives 3rd and 4th pairs of lumbar veins. “c” From the anastomosis between right supracardinal and right subcardinal veins: This part receives right gonadal vein. “d” From the upper part of right subcardinal vein: This part receives right suprarenal and both renal veins. “e” From a new vessel: It develops behind the liver and communicates right subcardinal vein with common hepatic vein also called hepatocardiac channel. “f” From the common hepatic vein: It is developed from suprahepatic part of right vitelline vein. The post-renal segment of the vena cava lies on a more posterior plane than the pre-renal segment.

Abdomen

3

Fig. 23.21: Development of inferior vena cava

D. Anomalies a. Double inferior venae cavae below the renal veins. b. Retrocaval ureter.

Posterior Abdominal Wall

287

3. Applied anatomy ¾ In obstruction of inferior vena cava, a collateral circulation may be established. The tributaries of superior and inferior venae cavae are communicated by a number of superficial and deep sets of veins. ¾ Thrombosis in the inferior vena cava causes oedema of legs and back. OLA-36 Cisterna chyli

Introduction: It is dilated lymphatic sac. 1. Length: 5 cm 2. Site: In front of bodies of L1 and L2. 3. Tributaries A. Intestinal lymph trunk B. Right and left lumbar trunks. SN-59

Cisterna chyli

1. Gross anatomy A. It is an elongated lymphatic sac. B. Length: 5 to 7 cm. C. Situation: In front of 1st and 2nd lumbar vertebrae, immediately to the right of the abdominal aorta.

Abdomen

3

Fig. 23.22: Formation and tributaries of cisterna chyli

2. Relations A. Right a. Right crus of diaphragm b. Lumbar azygos vein B. Left a. Left crus of diaphragm b. Abdominal aorta c. Coeliac trunk d. Superior mesenteric artery

288

Exam-Oriented Anatomy

C. Posterior a. Anterior longitudinal ligament b. Bodies of L1 and L2 c. Intervertebral disc between L1 and L2 3. Tributaries: Right and left intestinal lymph trunks.

Abdomen

3

Fig. 23.23: Afferent lymphatics of cisterna chyli

4. Termination: Its upper end continues as thoracic duct. 5. Draining areas: Intestinal trunk brings lymph from A. The stomach to intestine B. Pancreas C. Spleen D. Anteroinferior part of the liver E. All structures below diaphragm (lower half of the body). 6. Applied anatomy ¾ Thoracic duct when obstructed due to filarial infestation or growth will give rise to chylothorax, chyluria, etc. ¾ Thoracic duct when damaged during operation in the neck the lymph usually follows another channel, but if it fails, then chylous fistula may result.

24 Perineum

OLA-37 Enumerate the structures piercing the perineal membrane in male

1. Urethra in the midline. 2. Ducts of bulbourethral gland. 3. Arteries A. Artery to the bulb, B. Urethral artery, a branch of artery of penis C. Deep artery of penis (a branch of perineal artery), and D. Dorsal artery of penis. E. Posterior scrotal artery, a branch of perineal artery (a branch of internal pudendal artery). 4. Nerves A. Nerve to the bulb, a branch of nerve to bulbospongiosus (a branch of perineal nerve). B. Posterior scrotal nerve. C. Branches of perineal nerve to the superficial perineal muscle. SN-60

Perineal body (central perineal tendon)

Introduction: It is a pyramidal fibromuscular mass situated in the midline of perineum. 1. Location A. Male : It is located close to the bulb of penis. B. Female

: It is present between anal canal and pudendal cleft.

Fig. 24.1: The ball represents perineal body and fingers of the hands represent levator ani muscle 289

290

Exam-Oriented Anatomy

2. Formation: It is formed by 10 muscles—4 paired and 2 unpaired. BSNL A. Paired Bulbospongiosus. Superficial transverse perinei. Deep transverse perinei. Levator ani. B. Unpaired a. Perineal body is also called “obstetrical perineum” b. It is a musculofascial structure. c. Fascia I. Two layers of superficial perineal fascia i. Superficial fatty layer ii. Deep membranous layer II. Two layers of urogenital diaphragm i. Superior layer of urogenital diaphragm ii. Inferior layer of urogenital diaphragm d. Muscles: They are arranged in three layers (Fig. 24.2). I. Deep layer: Paired levator ani II. Intermediate layer Table 24.1: Paired and unpaired muscles of perineal body of three layers.

Abdomen

3

Layers

Paired

• Deep layer

• Levator ani

• Intermediate layer • Deep transverse perinei

• Superficial

Unpaired — • Deep part of external anal sphincter • Superficial part of external anal sphincter

• Bulbospongiosus • Superficial transverse perinei

Fig. 24.2: Muscles forming the perineal body

Perineum

291

3. Development: It develops from the tip of the urorectal septum. 4. Applied anatomy ¾ In female

, it acts as a very important support for the pelvic organs.

¾ Injury to the perineal body may weaken the pelvic floor and leads to prolapse of the vagina and uterus. ¾ Episiotomy (incision of vulva) is given to facilitate the labour. It prevents the rupture of the perineal body. ¾ The torn perineal body during parturition, if not properly repaired, leads to wider hiatus urogenitalis. OLA-38 Attachments and nerve supply of external anal sphincter

1. External anal sphincter is divided into three parts. A. Subcutaneous part: It is situated deep to the skin and is separated by perianal fascia. B. Intermediate or superficial part: It extends from perineal body to the tip of coccyx. C. Deep part: It encircles the upper part of the anal canal. 2. Nerve supply : It is supplied by pudendal nerve (somatic nerve). External anal sphincter

1. Formation: It is formed by the skeletal muscles. A. Control: It is under voluntary control. B. Extent: It surrounds the whole anal canal. C. Function: It keeps the anus and anal canal closed.

Fig. 24.3: External anal sphincter

2. History A. Old view: It has three anatomical (structural) and physiological (functional) components a. Subcutaneous, b. Intermediate, and c. Deep. B. Recent view: It is a single anatomical and physiological unit

3 Abdomen

SN-61

292

Exam-Oriented Anatomy

3. Gender variations Table 24.2: Features of external anal sphincter of male and female (Figs 24.4 and 24.5) Features

Male

Female

• Fate of transverse perinei and bulbospongiosus

• End in centre of perineum

• Fuse with external anal sphincter in lower part of perineum

• Surgical plane between urogenital triangle and anal canal

• Present

• Absent

• Puborectalis

• Uniform thickness and length in anterior and posterior part

• Anterior portion is narrow and shorter

• Puborectalis and external anal sphincter

• It is part of external anal sphincter

• It is separate from external anal sphincter

Abdomen

3 Fig. 24.4: Relations of puborectalis and external anal sphincter

Cat of nine tails—Tip Box 24.1 Perineal body is formed by 9 muscles 1. Four paired A. Bulbospongiosus B. Superficial transverse perinei C. Levator ani D. Deep transverse perinei 2. Unpaired—1 A. External anal sphincter

Abdomen

Fig. 24.5: Anatomy of external anal sphincter

Perineum 293

3

294

Exam-Oriented Anatomy

Table 24.3: External anal sphincter in male and female Particulars

Male

Female

Puborectalis

Continuous with external anal sphincter

Isolated

Anterior and posterior parts

Equal

Not equal

4. Parts: It is divided into three parts A. Subcutaneous part a. It is below the level of internal anal sphincter. b. It is separated from anal epithelium by submucosa. c. It is formed by flat bands. d. It is 15 mm in breadth. e. It surrounds the lower part of the anal canal. f. It is situated deep to the skin and is separated by perianal fascia. B. Intermediate or superficial part a. It extends from perineal body to the tip of coccyx. b. It is separated from subcutaneous part by perianal fascia. c. It is separated from internal anal sphincter by conjoint fibres of levator ani and longitudinal muscle of the rectum and anal canal. C. Deep part: It encircles the upper part of the anal canal.

Abdomen

3

5. Nerve supply : It is supplied by pudendal nerve (somatic nerve S2, S3, S4). OLA-39 Boundaries of ischiorectal fossa

Boundaries 1. Apex: It is formed by the junction of the obturator and anal fascia (inferior fascia of the pelvic diaphragm). 2. Base: It is formed by the skin. 3. Anterior: Posterior border of the perineal membrane. 4. Posterior A. Lower border of the gluteus maximus. B. Sacrotuberous ligament. 5. Lateral wall A. Obturator internus. B. Obturator fascia. C. Medial surface of ischial tuberosity. 6. Medial wall A. In the lower part: External anal sphincter. B. In the upper part: Levator ani. Refer Fig. 28.8

Perineum

295

OLA-40 Contents of ischiorectal fossa

1. Pudendal canal with its content. A. Pudendal nerve (ventral division of ventral ramus of S2, S3 and S4). B. Internal pudendal vessels (anterior division of internal iliac artery). 2. Posterior scrotal nerve and vessels. 3. Perforating cutaneous branch of S2, S3. 4. Inferior rectal nerve and vessels (S2, S3, S4). 5. Pad of fat. 6. Perineal branch of S4 nerve. It supplies anterior part of external anal sphincter. LAQ-23 Describe ischiorectal fossa under following heads 1. Gross anatomy, 2. Boundaries, 3. Contents, 4. Recesses, 5. Spaces, 6. Canals, and 7. Applied anatomy.

in the lateral part of anal

shaped space present

.

1. Gross anatomy (Fig. 24.6) A. Location: It is present 1 on either side of anal canal and below the pelvic diaphragm. B. Dimension: Length × width × depth 2” × 1” × 2” 2. Boundaries A. Apex: It is formed by the junction of the obturator and anal fascia (inferior fascia of the pelvic diaphragm). B. Base: It is formed by the skin. C. Anterior: Posterior border of the perineal membrane. D. Posterior a. Lower border of the gluteus maximus b. Sacrotuberous ligament. E. Lateral wall a. Obturator internus. b. Obturator fascia. c. Medial surface of ischial tuberosity. F. Medial wall a. In the lower part: External anal sphincter b. In the upper part: Levator ani.

3 Abdomen

Introduction: It is also called ischioanal fossa. It is the wedge

296

Exam-Oriented Anatomy

3. Contents A. Pudendal canal with its content. a. Pudendal nerve (ventral division of ventral rami of S2, S3 and S4). b. Internal pudendal vessels (anterior division of internal iliac artery). B. Posterior scrotal nerve and vessels. C. Perforating cutaneous branch of S2, S3. D. Inferior rectal nerve and vessels. E. Pad of fat. F. Perineal branch of S4 nerve. It supplies anterior part of external anal sphincter.

Abdomen

3

Fig. 24.6: Ischiorectal fossae

4. Recesses: These are narrow extensions of ischiorectal fossae (Fig. 24.7). A. Anterior recess: It extends from the urogenital diaphragm. It reaches up to the posterior surface of the body of pubis. B. Posterior recess: It is smaller than anterior. It is present deep to the sacrotuberous ligament. C. Horseshoe recess: It connects two ischiorectal fossae behind the anal canal.

Fig. 24.7: Recesses of ischiorectal fossae

Perineum

297

5. Spaces A. Perianal space a. Perianal fascia is a septum which separates the perianal space from the ischiorectal space. b. It extends from the white line of Hilton medially to the pudendal canal laterally. c. The fat is arranged tightly in the small loculi. d. The infections of this space are, therefore, very painful. It is due to the tension caused by swelling. B. Ischiorectal space a. It is deep to the perianal space. b. The fat is arranged loosely due to incomplete septa. c. The infections of this space are less painful since there is no tension in the swelling. d. Lunate fascia arches over ischiorectal fat and divides it into I. Suprategmental space. II. Tegmental space 6. Canals (fascial canal, Alcock’s canal): It is the connective tissue sheath in the lower lateral wall of the ischiorectal fossa. 7. Applied anatomy

SN-62

Pudendal canal (fascial canal, Alcock’s canal)

Introduction: It is the connective tissue sheath in the lower lateral wall of the ischiorectal fossa. 1. Location: 2.5 cm above the ischial tuberosity. 2. Formation (Fig. 24.8) A. Laterally: Obturator fascia. B. Above: Lunate fascia. C. Below: Falciform process of sacrotuberous ligament. D. Medially: Perianal fascia. E. Extent: From lesser sciatic foramen to deep perineal pouch.

3 Abdomen

¾ It allows distension of anal canal during passage of faeces. It also allows dilatation of the vagina during parturition. ¾ The loss of the fat results into prolapse of rectum. ¾ The perineal and ischiorectal spaces are common sites for abscesses. Through the horseshoe recess, unilateral abscess may become bilateral. ¾ Presence of hiatus of Schwalbe: It is a gap at the apex of the fossa. It is due to defective origin of levator ani from obturator fascia. It is occasionally present. Very rarely pelvic organ may herniate through it into the ischiorectal fossa. ¾ Psoas abscess may enter the iliac fossa. It may travel the ischiorectal fossa along the pudendal vessels. ¾ An abscess in the ischiorectal space may burst in the anal canal and produces fistula in ano.

298

Exam-Oriented Anatomy

Fig. 24.8: Arrangements of pudendal canal

3. Contents A. Pudendal nerve (S2–S4 ventral division of ventral rami), and B. Internal pudendal vessels. C. The arrangement of the structures within the canal are as follows from above downwards a. Dorsal nerve of penis or clitoris. b. Internal pudendal vein. c. Internal pudendal artery. d. Perineal nerve.

Abdomen

3

4. Applied anatomy : Pudendal nerve is blocked to anaesthetize the perineum. This is called pudendal block. It is given by following methods. ¾ Transvaginal procedure: A long needle is passed, through the vaginal wall and guided by a finger to the ischial spine. It can be palpated per vaginal. ¾ Perineal procedure: The ischial tuberosity is palpated subcutaneously through the buttock. The needle is inserted into the pudendal canal along the medial side of the tuberosity. The canal lies about 1” (2.5 cm) deep to ischial tuberosity. LAQ-24 Describe internal pudendal artery under 1. Origin, 2. Termination, 3. Gender variation, 4. Extent, 5. Course 6. Relations, 7. Branches and distribution, and 8. Applied anatomy.

1. Origin: It is one of the smaller terminal branches of the anterior division of the internal iliac artery. It arises in the pelvis just below the origin of the obturator artery. 2. Termination: It continues as artery of penis/clitoris distal to the perineal branch of internal pudendal artery. 3. Gender variation: It is larger in males than in females .

299

4. Extent: It extends from the origin to the initial part of deep perineal pouch. 5. Course: It is divided in three parts by sacrospinous ligament (Fig. 24.9). A. First part is proximal to sacrospinous ligament. It is also called pelvic part. B. Second part is deep to sacrospinous ligament. It is present in gluteal region. C. Third part is distal to sacrospinous ligament. It is also called part of internal pudendal artery in pudendal canal. 6. Relations A. First part (intrapelvic part) a. The artery runs downwards in the pelvis. b. It runs in front of the I. Piriformis, II. Sacral plexus, and III. Inferior gluteal artery. c. It leaves the pelvis by piercing the parietal pelvic fascia. d. It passes through the greater sciatic foramen, below the piriformis. e. It thus enters the gluteal region. B. Second part (part present in gluteal region) a. The artery crosses the tip of the ischial spine. b. It is under cover of the gluteus maximus. c. Here it lies between the I. Pudendal nerve medially, and II. Nerve to the obturator internus laterally. d. It leaves the gluteal region by passing through the lesser sciatic foramen. e. It enters the pudendal canal. C. Third part (part of internal pudendal artery in pudendal canal) a. The artery runs downwards and forwards in the lateral wall of the ischioanal fossa. b. It is about 4 cm above the lower margin of the ischial tuberosity. c. It is related to the I. Dorsal nerve above, and II. Perineal nerve below. In deep perineal space, it is called artey of penis/clitoris. a. The artery of the penis or clitoris is continuation of internal pudendal artery. b. It runs forwards close to the side of pubic arch. c. It lies medial to the dorsal nerve of penis or of clitoris. d. The artery ends a little behind the arcuate pubic ligament. e. It divides into the deep and dorsal arteries of penis, clitoris. 7. Branches and distribution (Fig. 24.9): Branches are grouped for the purpose of convenience. They are branches given in relation to

3 Abdomen

Perineum

300

Exam-Oriented Anatomy

A. Pudendal canal, B. Deep perineal pouch, and C. Terminal branches. To be precise, the branches arising in pudendal canal are branches of internal pudendal artery. The arteries arising distal to pudendal canal are branches of artery of penis/clitoris. MCQ—Tip Box 24.2 Please note that, all the branches of internal pudendal artery except inferior rectal artery pierce perineal membrane.

Abdomen

3 Fig. 24.9: Course and branches of internal pudendal artery

A. Branches are given at two ends of pudendal canal. They are a. Inferior rectal artery at posterior end. b. Perineal artery at anterior end of pudendal canal. a. Inferior rectal artery accompanies the nerve of the same name. It supplies the I. Perianal skin, II. Sphincters of the anus, and the III. Anal canal below the pectinate line. Here it anastomoses with the branches of the superior rectal artery. b. Perineal branch pierces the urogenital diaphragm. I. Distribution: It supplies the i. Bulbospongiosus and ii. Ischiocavernous muscles. II. Course: It runs forwards into the superficial perineal space, superficial to perineal membrane. It divides into i. Posterior scrotal or labial branches, and

Perineum

301

ii. Transverse perineal branch. • Posterior scrotal artery or labial branch supply tissues between the anus and the bulb. • Transverse perineal branch runs medially along the superficial transverse perinei muscle. B. Branches given from internal pudendal artery in the deep perineal pouch are branches of arteries of penis/clitoris. a. The artery to bulb of penis, and b. Urethral artery. a. The artery of the bulb passes medially through the deep transverse perineal muscle. It reaches the bulb of the penis after piercing the perineal membrane. It supplies the I. Posterior part of corpus spongiosum, II. Bulbourethral gland, and III. Proximal half of the corpus spongiosum. b. The urethral artery arises just below the perineal membrane. It passes through the fascia of the urogenital diaphragm. It enters the corpus spongiosum and reaches the glans penis. It is distributed to the urethra and the erectile tissue around it. C. Terminal branches are two b. Dorsal arteries of the penis. a. Deep arteries are also called cavernosal arteries. I. Features i. They are larger of the two terminal branches of internal pudendal/ artery of penis/clitoris. ii. They are given behind the pubic angle. iii. They pierce perineal membrane. II. They are the principal arteries for filling the lacunae of erectile tissue during erection of the penis. III. Each deep artery of the penis runs lengthwise in corpus cavernous and gives off numerous branches. IV. These arteries give rise to minute arteries that directly open into the cavernous spaces. V. In the flaccid state of the penis, these vessels project in the lacunae as looped or spiral vessels and hence termed “helicine arteries.” b. Dorsal artery of the penis or of the clitoris I. Features i. It is the smaller of the two terminal branches of internal pudendal/ artery of penis/clitoris.

3 Abdomen

a. Deep arteries of the penis, and

302

Exam-Oriented Anatomy

ii. It is given behind the pubic angle. iii. It traverses sphincter urethrae and then pierces perineal membrane. II. It passes upward between the crura of penis or clitoris. III. It runs on the dorsal surface of the penis or the clitoris beneath the deep fascia of penis called Buck’s fascia. The dorsal artery runs on the dorsal aspect of the penis. IV. It runs lateral to the deep dorsal vein, and medial to the dorsal nerve of penis. V. It supplies circumflex branches to the corpora cavernosa and corpus spongiosum. VI. Therefore, corpora cavernosa receives blood both from the deep and the dorsal arteries of the penis. VII. The circumflex branches end by anastomosing in the coronal sulcus. VIII. They supply the glans penis and its overlying skin. Names get change after particular events, landmarks Box 24.3 Note: The artery of penis is the continuation of pudendal artery distal to the perineal branch. The pudendal artery is called artery of penis in deep perineal space.

Abdomen

3

8. Applied anatomy ¾ During dissections of the anal canal, the inferior rectal vessels are encountered in the ischioanal fossa. They must be secured before division. They tend to retract laterally to the canal, where they can cause troublesome bleeding. ¾ The common cause of painful swelling in the perineum is perineal abscess. It is due to the infection carried by a small branch of internal pudendal artery. ¾ There may be infection during episiotomy. This may interrupt the blood flowing through the internal pudendal artery. This results in painful perineal swelling. “Know the vessels n nerve ur ashamed off”—Tip Box 24.4 Introduction: The internal pudendal artery: The word pudendal means ashamed off. It supplies all the structures that we are ashamed off. It is also the chief artery of urogenital . The structures supplied by internal pudendal artery include major portion of the skin and all of the deeper structures, including the erectile tissue of the penis/clitoris. However, the testis, epididymis, and the scrotal layers surrounding these have their own blood supply.

303

Perineum

A tale of internal pudendal artery—Tip Box 24.5 Simile of internal pudendal artery A house has 3 rooms. They are room R1, R2 and R3. • The R1 has 2 windows W1 and W2. • There is a water tank near the roof and a canal. • The canal is fixed to the lower part of outer wall of R1. • The water tube is called A. • The area outside the house near the window represents gluteal region. • The water passes from the roof of R1 to R3.

W1

R1

R2

R3

W2

B5 B6

B1

B2

C

B3

B4

Simile of internal pudendal artery Representation

W1

Greater sciatic foramen

W2

Lesser sciatic foramen

3 Abdomen

Aberration

Area outside the wall having windows—gluteal region R1

Pelvis

R2

Deep perineal pouch

R3

Superficial perineal pouch

P1

Urogenital diaphragm

P2

Perineal membrane

P3

Colles’ fascia.

Branches of internal pudendal artery Aberration Site B1 Posterior part of pudendal canal B2 B3 B4 B5 B6

Deep perineal pouch

Terminal

Type

Branch Inferior rectal artery

Collateral

Perinatal branch Artery to bulb of penis Urethral artery Dorsal artery of penis Deep artery

304

Exam-Oriented Anatomy

Box 24.6 Note: Please do watch animation video of Simile of internal pudendal artery (AA31) of 4.40 minutes duration on CBSiCental App. OLA-41 Structures piercing perineal membrane in female

Following are the structures piercing perineal membrane in female . Refer Fig. 24.13 1. Urethra, 2. Vagina, 3. Arteries A. Artery to the bulb of the vestibule, B. Deep artery of clitoris, C. Dorsal artery of clitoris and D. Posterior labial arteries. 4. Nerves A. Nerve to bulb of vestibule, B. Posterior labial nerve, and C. Muscular branches of perineal nerve supplying superficial perineal muscles. OLA-42 Perineal membrane

Abdomen

3

It is an unyielding sheath of fibrous tissue which separates superficial and deep perineal pouch. It forms the inferior boundary of deep perineal pouch and superior boundary of superficial perineal pouch.

Fig. 24.10: Perineal membrane

SN-63

Urogenital diaphragm

Introduction: It is a musculofascial partition across the pubic arch and separates the pelvic cavity from the anterior part of the pelvic outlet.

Perineum

305

1. Formation (Fig. 24.11) A. Sphincter urethrae: It encircles the membranous urethra and consists of superficial and deep fibres. B. Deep transversus perinei

Fig. 24.11: Urogenital diaphragm

B. Female

: Vagina and urethra.

4. Relations A. Below: Contents of superficial perineal pouch. B. Above a. Apex of prostate (in male

) or neck of the urinary bladder (in female

).

b. Anterior fibres of both levator ani muscles. c. Anterior recesses of ischiorectal fossae. C. In front: A lar gap between arcuate pubic ligament and transverse perineal ligament. It transmits the deep dorsal vein of penis or clitoris. D. Behind: Ischiorectal fossae and their contents. 5. Actions A. It supports the prostate or the bladder. B. In female , it constricts the vagina. C. It fixes the perineal body. D. Sphincter urethrae exerts voluntary control of micturition and expels the last drops of semen and urine.

3 Abdomen

2. Nerve supply : Both muscles are supplied by muscular branches of the perineal nerve, branch of pudendal nerve. 3. Structure piercing in A. Male : Urethra.

306

Exam-Oriented Anatomy

6. Rupture of the urethra is common beneath the pubis by fall on the sharp object. This causes extravasation of the urine. ¾ Rupture of urethra, superficial to the perineal membrane results in extravasation of the urine in the superficial perineal pouch. It accumulates in the scrotum> penis>anterior abdominal wall, >deep to fascia of Scarpa and extends up to axilla. ¾ Rupture of the urethra, deep to the perineal membrane produces extravasation of the urine in the extraperitoneal space of the pelvis. It accumulates in the anterior abdominal wall. SN-64

Perineal membrane (inferior fascia of urogenital diaphragm)

Introduction: It is an unyielding sheath of fibrous tissue. It separates superficial and deep perineal pouches. It forms the inferior boundary of deep perineal pouch and superior boundary of superficial perineal pouch.

Abdomen

3

1. Gross A. Dimensions: Anteroposterior dimension 3.5 cm. B. Disposition: Horizontal in erect posture. C. Attachments a. Anteriorly and on either side: Ischiopubic rami. b. Posteriorly and on either side: Anterior part of ischial tuberosity. c. Anterior border forms the transverse perineal ligament. d. Posterior border fuses to perineal body and superiorly to superior layer of urogenital diaphragm. e. It fuses inferiorly with Colles’ fascia. 2. Structures piercing A. In male a. Urethra in the midline, b. Ducts of bulbourethral gland, c. Arteries I. Artery to the bulb, II. Posterior scrotal artery, a branch of perineal artery (a branch of internal pudendal artery). III. Urethral artery, a branch of artery of penis IV. Deep artery of penis and (a branch of perineal artery). V. Dorsal artery of penis. d. Nerves I. Nerve to the bulb, a branch of nerve to bulbospongiosus (a branch of perineal nerve). II. Posterior scrotal nerve. III. Branches of perineal nerve to the superficial perineal muscle.

Perineum

307

Note: 1. The shape and size of perineal membrane in male is represented by the space present between index and middle fingers (Fig. 24.12). 2. The shape and size of perineal membrane in female is represented by the space present between index finger and thumb (Fig. 24.13).

B. In female a. Urethra, b. Vagina, c. Arteries I. Artery to the bulb of the vestibule, II. Deep artery of clitoris, III. Dorsal artery of clitoris, and IV. Posterior labial arteries. d. Nerves I. Nerve to bulb of vestibule, II. Posterior labial nerve, and III. Muscular branches of perineal nerve supplying superficial perineal muscles. 3. Applied anatomy : Urethra passing through the perineal membrane is called membranous urethra. It is the shortest and least dilatable part of urethra and does not contain any glands.

3 Abdomen

Fig. 24.12: Openings in the perineal membrane in male shown by index and middle finger of right hand. Index and middle fingers represent ischiopubic rami of left and right side, respectively

308

Abdomen

3

Exam-Oriented Anatomy

Fig. 24.13: Openings in the perineal membrane in female shown by thumb and index finger of right hand. Thumb and index finger represent ischiopubic rami of left and right side, respectively

LAQ-25 Describe superficial perineal pouch under following heads 1. Boundaries, 2. Contents, and 3. Applied anatomy.

Introduction: It is the space between the Colles’ fascia and the perineal membrane (inferior layer of urogenital diaphragm). 1. Boundaries: There are two ways of describing the boundaries of perineal pouch. In anatomical position, the terms superior or roof and inferior or floor are used. While dissecting, the terms superficial and deep are used (Fig. 24.14A). A. Superficially or floor by Colles’ fascia. B. Deep or roof by the perineal membrane. C. On each side by the ischiopubic rami. D. Posteriorly, the space is closed by fusion of the perineal membrane with Colles’ fascia. E. Anteriorly, it is opened. It is continuous with the spaces of the scrotum, the penis and the anterior abdominal wall.

Perineum

309

Abdomen

3 Fig. 24.14A: Boundaries and contents of superficial perineal pouch in male Table 24.4: The superficial perineal space—male Features

Male

Definition

This is the superficial space of the urogenital region situated superficial to the perineal membrane

Boundaries • Superficial • Deep • On each side • Posteriorly • Anteriorly

• • • • •

Contents

• Root of penis, made up of two

Colles’ fascia Perineal membrane Ischiopubic rami Closed by the fusion of perineal membrane with Colles’ fascia. Open and continuous with the spaces of the scrotum, penis and the anterior abdominal wall

Contd.

310

Exam-Oriented Anatomy

Table 24.4: The superficial perineal space—male (Contd.) Features

Male • Corpora cavernosa and one corpus spongiosum traversed by the urethra.

Abdomen

3

Muscles on each side

• Ischiocavernous covering the corpora cavernosa of penis. • Bulbospongiosus covering corpus spongiosum; both are united by a median raphe. • Superficial transversus perinei

Nerves

• Sets of branches from perineal nerve, namely – Posterior scrotal nerve – Branch to bulb and muscular branches – Long perineal nerve from posterior cutaneous nerve of thigh

Vessels

• Branches of perineal artery, namely, – Posterior scrotal and transverse perineal • Four branches from the artery of penis, namely, – Artery to the bulb of penis, – Urethral artery, – Deep, and – Dorsal arteries of penis.

Glands and ducts

• Only the ducts of bulbourethral glands Table 24.5: The superficial perineal space—female

Features

Female

Definition

This is the superficial space of the urogenital region situated superficial to the perineal membrane

Boundaries • Superficial • Deep • On each side • Posteriorly • Anteriorly

• • • • •

Colles’ fascia Perineal membrane Ischiopubic rami Closed by the fusion of perineal membrane with Colles’ fascia. Open and continuous with the spaces of the clitoris and the anterior abdominal wall

Contents

• Body of clitoris, made up only of two corpora cavernosa separated by an incomplete septum. • The corpus spongiosum is absent. • Urethral orifice lies 2 cm behind the clitoris. • Vaginal orifice lies just behind urethral orifice. • There are two bulbs of vestibule, one on each side of these two orifices. These unite and get attached to the glans clitoridis.

Muscles on each side

• • • •

Ischiocavernosus covering the corpora cavernosa of clitoris Bulbospongiosus covering bulb of vestibule. These remain separated to give passage to urethra and vagina Superficial transversus perinei Contd.

Perineum

311

Table 24.5: The superficial perineal space—female (Contd.) Features

Female

Nerves

• Sets of branches from perineal nerve, namely – Posterior labial nerve, – Branch to bulb of vestibule and muscular branches • Long perineal nerve from posterior cutaneous nerve of thigh

Vessels

• Branches of perineal artery, namely – Posterior labial, and – Transverse perineal • Four branches from the artery of clitoris, namely – Artery to bulb of vestibule, – Urethral artery, – Deep and – Dorsal arteries of clitoris

Glands and ducts

• Greater vestibular glands and them ducts

Abdomen

3

Fig. 24.14B: Boundaries and contents of superficial perineal pouch in female

312

Exam-Oriented Anatomy

2. Applied anatomy ¾ Injury to the bulb of penis causes rupture of superficial perineal pouch. It results from • Straddle injury (forceful blow to the perineum when sitting, standing or walking with legs apart.) • Creating false passage while passing transurethral catheter. • Rupture of blood vessel in superficial perineal pouch.

Fig. 24.15: Rupture of spongy urethra results in extravasation of urine into the superficial perineal pouch. This results from straddle injury, such as falling on a metal beam

Abdomen

3

¾ There is extravasation of urine in rupture of superficial perineal pouch. The direction of extravasated urine is decided by the attachment of perineal fascia. ¾ The direction of accumulation of urine is as follows • Loose connective tissue in scrotum > • Around penis > • Anterior abdominal wall deep to the membranous layer and superficial to rectus sheath > • May extend to axilla. ¾ The urine cannot pass • Into thighs because membranous layer blends with fascia lata. • Anal because superficial and deep layers of perineal fascia are continuous with each other. LAQ-26 Describe deep perineal pouch under following heads 1. Boundaries, 2. Contents, and 3. Applied anatomy.

Introduction: It is the space between superior and inferior fascia of urogenital diaphragm. 1. Boundaries A. Inferior or superficial layer is by perineal membrane (inferior layer of urogenital diaphragm).

Perineum

313

B. Superior or deep by the superior layer of urogenital diaphragm. C. On each side by the ischiopubic rami. D. Posteriorly, the space is closed by the union of the perineal membrane with the superior fascia of the urogenital diaphragm (fusion of superior and inferior layer of urogenital diaphragm). E. Anteriorly, it is closed by the union of perineal membrane with the superior fascia of urogenital diaphragm at the transverse perineal ligament. 2. Contents A. In male (Fig. 24.16A)

Abdomen

3

Fig. 24.16A: Boundaries and contents of deep perineal pouch in male

314

Exam-Oriented Anatomy

a. Structures I. Membranous urethra, and II. Bulbourethral gland. b. Muscles I. Sphincter urethrae. II. Deep transversus perinei. c. Nerves I. Dorsal nerve of the penis (pudendal nerve) II. Muscular branches from the perineal nerve. d. Vessels: Artery of penis, a branch of internal pudendal artery. B. In female

(Fig. 24.16B)

Abdomen

3

Fig. 24.16B: Boundaries and contents of deep perineal pouch in female

Perineum

315

a. Structures I. Urethra, and II. Vagina , b. Muscles I. Sphincter urethrae. II. Deep transversus perinei. c. Nerves I. Dorsal nerve of clitoris. II. Muscular branches from the perineal nerve. d. Vessels: Artery of penis, a branch of internal pudendal artery. 3. Applied anatomy ¾ Fracture of pelvic girdle is one of the causes of rupture of urethra in deep perineal pouch. The urine and blood accumulate in following sequence. • Deep perineal pouch • Around prostate • Around bladder ¾ Superficial to peritoneum and deep to rectus sheath.

Abdomen

3

Fig. 24.17: Structures in the deep perineal pouch

25 Urinary Bladder and Urethra

SN-65

Automatic bladder (neurogenic bladder, reflex bladder)

1. Definition: The bladder having no control over emptying of the urine is called automatic bladder. The capacity of bladder is reduced. The walls of urinary bladder are hypertrophied with some residual urine. It is also called spastic neurogenic bladder. 2. Causes: Lesion of the sacral portion of spinal cord causes automatic bladder. The lesion may be in the A. Cauda equine B. Conus medullaris C. Sacral roots or D. Pelvic nerve 3. Clinical manifestations: It is manifested by A. Loss of normal bladder sensations, B. Reflex activity, C. Inability to initiate urine, and D. Incontinence. OLA-43 What is the capacity of gallbladder and urinary bladder?

1. Gallbladder—30 to 50 ml 2. Urinary bladder: The capacity of bladder varies depending upon age and status of bladder. The figures are approximate. A. At birth 2 ounces (60 ml). B. The capacity when one feels sensations of filling the bladder—4 ounces (120 ml) C. The capacity when there is a desire to micturate—8 ounces (240 ml) D. The capacity of bladder when it becomes painful—16 ounces (480 ml) E. The maximum capacity of bladder (anatomical capacity)—32 ounces (960 ml) OLA-44 Nerve supply of urinary bladder

1. Nerve supply : PMT—Parasympathetic nerve 316

MT —Empties

Urinary Bladder and Urethra

317

Sympathetic has filling effect. A. Parasympathetic fibres, is main motor nerve of the bladder. It reaches via pelvic splanchnic nerve (nervi erigentes S2, S3, S4). It empties the bladder. Emptying of the bladder is done by a. Contraction of the detrusor muscle, and b. Relaxation of the internal urethral sphincter. B. Sympathetic fibres are derived from L1 and L2 segments of the spinal cord. For most of the bladder, the sympathetic fibres are vasomotor and have filling effect. Filling is done by a. Inhibition to the detrusor, and b. Relaxation of the sphincter vesicae. C. Somatic pudendal nerve: It supplies the external urethral sphincter (sphincter urethrae) which is voluntary. D. Sensory nerves: These are carried mainly by parasympathetic nerves and partly by sympathetic nerves. a. Pain sensation is carried by the lateral spinothalamic tract. b. Distension of bladder is carried by the posterior column.

Abdomen

3

Fig. 25.1: Nerve supply of the urinary bladder

LAQ-27 Describe urinary bladder under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

318

Exam-Oriented Anatomy

Introduction: It is muscular reservoir of urine present in the anterior part of pelvic cavity. 1. Gross anatomy A. Location: It is present behind the pubic symphysis, in the anterior part of pelvic cavity. a. Capacity:

2, 4, 8, 16, 32

• At birth, it is 2 ounces (60 ml). • When the capacity of the bladder reaches 4 ounces (120 ml), one gets sense of filling the bladder. • When the bladder is filled beyond 8 ounces (240 ml), one gets desire to micturate. • When the capacity of the bladder reaches 16 ounces (480 ml), it becomes painful. • The anatomical capacity of bladder is 32 ounces (960 ml). B. External features (Fig. 25.2) a. Shape I. In empty, it is tetrahedral

.

II. In distended, it is ovoid

Abdomen

3

b. Apex I. In empty, it is directed forward. II. In distension, it is directed towards the umbilicus. c. Base is directed backwards. d. Neck is the lowest and most fixed part of the bladder. e. Surfaces

Fig. 25.2: External features of bladder

C. In empty a. Superior, and b. Inferolateral surfaces.

Urinary Bladder and Urethra

319

D. In distended bladder a. Anterior, and b. Posterior. E. Borders: Four a. Left lateral, b. Right lateral, c. Posterior, and d. Anteroinferior. F. Relations (Figs 25.3 to 25.5 and Table 25.1)

Fig. 25.3: Relations of urinary bladder in male

Fig. 25.4: Relations of urinary bladder in female

Abdomen

3

320

Exam-Oriented Anatomy

Fig. 25.5: Relations of posterior surface of the bladder Table 25.1: Relations of urinary bladder

Abdomen

3

Particulars

Female

Male

• Apex

• Connected to umbilicus by median umbilical ligament

• Base

• Cervix of uterus • Vagina

• Separated from rectum in upper part by rectovesical pouch—coils of intestine • In lower part by seminal vesicle: “Vas deferens”

• Neck—lower

• Pelvic fascia which surrounds upper part of urethra

• Base of prostate

• Superior surface • Greater part is covered by periis covered by toneum and is related to vesicoperitoneum uterine pouch and contains – Sigmoid colon – Terminal part of ileum

• Completely covered by peritoneum and is in contact with – Sigmoid colon – Terminal part of ileum

• Inferolateral surfaces are evoid of peritoneum

• • • • •

• It is related to pubis • Pubovesical ligament • Retropubic fat • Levator ani • Obturator internus

Pubis Puboprostatic ligament Retropubic fat Levator ani Obturator internus

G. Blood supply a. Arterial supply I. Major blood supply to the bladder is by i. Superior vesical artery, a branch of anterior division of internal iliac artery. ii. Inferior vesical artery, a branch of anterior division of internal iliac artery. II. Minor blood supply to the lower part of the bladder is from i. Obturator artery, a branch of anterior division of internal iliac artery. ii. Inferior gluteal artery, a branch of anterior division of internal iliac artery. iii. Uterine artery, a branch of anterior division of internal iliac artery. iv. Vaginal artery, a branch of anterior division of internal iliac artery.

Urinary Bladder and Urethra

321

b. Venous drainage : Veins of the bladder do not follow the arteries. They vary in male

and female

.

: Veins form a vesicoprostatic plexus. It is present between bladder I. In male and prostate, which drains backwards to the internal iliac vein. II. In female : Veins form a plexus in the base of the broad ligament. It drains backward to the internal iliac vein. H. Nerve supply : It is mainly by

I. Lymphatic drainage : The lymphatics of the bladder follow the course of the arteries and drain into internal and external iliac nodes. A few vessels may pass to the internal iliac nodes or to the lateral aortic nodes. Lymphatics drain alongside the vesical blood vessels to the iliac; and then para-aortic nodes. 2. Histology : The wall of the bladder presents following coats from outside inward. A. Serous coat: It is lined by simple squamous epithelium. It is present only on the superior surface of urinary bladder. In other places, it is formed by adventitial coat. B. Muscular coat: It possesses three ill-defined layers of smooth muscle. a. Outer longitudinal, b. Middle circular, and c. Inner longitudinal. C. Mucosa: It consists of a. Transitional epithelium, which consists of I. Deep layer. It is formed by columnar cells. II. Middle layer. It is formed by polyhedral cells.

3 Abdomen

a. Parasympathetic fibres, which provide main motor innervation of the bladder. It reaches via pelvic splanchnic nerve (nervi erigentes S2, S3, S4). The emptying of the bladder is done by parasympathetic fibres. I. Contraction of the detrusor muscle, II. Relaxation of the internal urethral sphincter. b. Sympathetic fibres are derived from L1 and L2 segments of the spinal cord. For most of the bladder, the sympathetic fibres are vasomotor and have filling action. This is achieved by I. Inhibition to the detrusor, and II. Motor to the sphincter vesicae. c. Somatic pudendal nerve (S2, S3, S4). It supplies the external urethral sphincter (sphincter urethrae) which is voluntary. d. Sensory nerves: These are carried mainly by parasympathetic nerves and partly by sympathetic nerves. i. Pain sensation is carried by the lateral spinothalamic tract. ii. Distension of bladder is carried by the posterior column.

322

Exam-Oriented Anatomy

III. Superficial layer. It is formed by umbrella

shaped cells in empty

bladder. In distended bladder, the cells are squamous type. D. Lamina propria: Muscularis mucosa is absent.

Abdomen

3

Fig. 25.6: Histology of urinary bladder

3. Development A. Chronological age: It develops in the 4th to 7th weeks of intrauterine life. B. Germ layer a. The epithelium of the bladder develops from endoderm and mesoderm. b. The muscles develop from the mesoderm. C. Site: Cloaca. D. Source a. Epithelium of the urinary bladder I. Except trigone develops from cranial part of vesicourethral canal (endoderm). II. Epithelium of trigone develops from absorbed part of mesonephric duct (mesoderm). b. The muscles and the connective tissue develop from intra-embryonic splanchnopleuric mesoderm. E. Anomalies • Absence of the urinary bladder. ABCDEF • Bladder may be divided into upper and lower compartments by septum (hour glass bladder)

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323

• There may be Communication with the rectum—vesicorectal fistula. • Diverticulum of the urinary bladder. It is usually at the junction of trigone and rest of the bladder. • Ectopic vesicae: The lower part of the anterior abdominal wall is absent, the bladder is exposed on the surface of the body. • Fistula: Allantois may remain patent entirely and urine passes through umbilicus. 4. Applied anatomy ¾ Lesion of the parasympathetic nerve causes • Loss of control of the micturition, • Retention of urine due to over activity of sympathetic nerve. ¾ Lesion of the sympathetic nerve fibres causes paralysis of the sphincter vesicae. It results into dribbling of urine. ¾ Lesion of both pyramidal tracts (upper motor neuron lesion) results into loss of voluntary control of micturition. ¾ Bilateral anterolateral cordotomy results into abolition of pain sensation. There is absence of awareness of bladder filling. There is no sensation of desire to micturate. This is present in advance stage of cancer of the bladder. ¾ In posterior column lesion (tabes—wasting dorsalis—dorsal column), the bladder is atonic and large quantity of urine is collected without any reflex contraction. Female

urethra

1. Dimensions A. 4 cm long. B. 6 mm in diameter 2. Extent A. From internal urethral orifice of bladder B. To external urethral orifice.

Fig. 25.7: Female urethra

3 Abdomen

SN-66

324

Exam-Oriented Anatomy

3. Course: It A. Begins at the internal urethral orifice. It is approximately opposite of the middle of the pubic symphysis. B. Runs anteroinferiorly behind the symphysis pubis. C. Is embedded in anterior wall of vagina. D. Crosses the perineal membrane and ends at external urethral orifice. E. Ends as an anteroposterior slit. F. Lies anterior to the opening of vagina, about 2.5 cm behind glans clitoris. 4. Interior A. Lined by simple mucous secreting glands. B. Anterior and posterior walls of canal possesses a ridge. It is called urethral crest. C. Features in urethra a. Pit-like recess b. Mucous urethral glands, c. Paraurethral duct. d. Paraurethral glands lie the submucous tissue. They open in lateral wall margin of external urethral orifice. 5. Blood supply

Abdomen

3

A. Arterial supply : a. Superior vesical artery, branch of anterior division of internal iliac artery. b. Vaginal artery branch of anterior division of internal iliac artery. B. Venous drainage : Vesical plexus around urethra > Vesical venous plexus > internal pudendal vein > internal iliac vein 6. Lymphatic drainage : External and internal iliac lymph nodes. 7. Nerve supply A. Sympathetic: Postganglionic sympathetic fibres arise from plexus around vaginal arteries. B. Parasympathetic a. Preganglionic fibres arise from S2, S3, and S4 segments of spinal cord. b. Synapse in the vesical plexus. c. Postganglionic fibres reach smooth muscles of urethra. C. Somatic fibres from S2, S3, and S4 segments of spinal cord. D. Sensory fibres through pelvic splanchnic nerve. 8. Applied anatomy : The catheterization of urethra is much easier in the females than in the males

.

Urinary Bladder and Urethra

LAQ-28 Describe male

325

urethra under following heads

1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: It is a common tubular passage for the elimination of urine and semen. It extends from internal urethral orifice to the external urethral orifice at the tip of the penis. 1. Gross anatomy A. Dimensions a. Length: 18 to 20 cm b. Curvatures: There are two curvatures. B. Divisions a. Prostatic part of the urethra. I. Situation: It is present in the prostate gland.

Abdomen

3

Fig. 25.8: Course of male urethra

II. Peculiarity : It is the widest and most dilated part of the male urethra. It is the narrowest at the junction with the membranous urethra. III. Internal features: Posterior wall of the prostatic urethra shows following features. i. The urethral crest, a median longitudinal ridge of mucous membrane. ii. The colliculus seminalis, an elevation on the middle of the urethral crest. iii. The prostatic utricle, a blind sac about 6 mm long, which lies within the prostate. • There is an orifice on the elevation through which prostatic utricle opens into the urethra.

326

Exam-Oriented Anatomy

• On each side of this orifice, there are openings of the ejaculatory ducts. There are two vertical grooves situated one on each side of urethral crest. They are called prostatic sinuses. • Each sinus presents the openings of 20 to 30 prostatic glands. b. Membranous part of urethra I. Introduction: It passes through the deep perineal space and pierces the perineal membrane. i. It is about 2.5 cm below and behind the pubic symphysis. ii. It is the 2nd narrowest and least dilatable part of the male urethra (Fig. 25.9). iii. It is surrounded by sphincter urethrae (external urethral sphincter). iv. The bulbourethral glands are placed one on each side of the membranous urethra and their ducts open into the spongy part of urethra.

Abdomen

3 Fig. 25.9: Male urethra

II. Internal features: There are many urethral glands. They open into the membranous part of urethra. c. Spongy or penile part of the urethra I. Introduction: It is so-called because it lies in the corpus spongiosum of penis. II. Situation: It lies in the corpus spongiosum. It courses through i. Superficial perineal pouch, ii. Body of penis, and iii. Glans penis. III. Extent i. Begins from the membranous urethra (from perineal membrane).

Urinary Bladder and Urethra

327

• Ends: It opens to the exterior by an orifice called the external urethral orifice. It is a vertical slit of 6 mm long. It is the narrowest part of the urethra. • It is guarded by two lips called labia. IV. Dimension i. Length: 15 cm. ii. Diameter: 6 mm in the body of penis. V. Course: It first ascends upwards and forwards in the superficial pouch up to the symphysis pubis. It descends down in the flaccid condition of the penis. VI. Dilatations i. Intrabulbar fossa: It lies in the bulb of the penis. It bulges into the floor and on each side. Hence, looks like a trapezium in cross-section. ii. Fossa terminalis: It is also called fossa navicularis. It lies within the glans penis. C. Blood supply a. Arterial supply : There is no single artery to the urethra. The arteries arise from many sources. They are

b. Venous drainage : It is divided into I. Anterior urethra is drained by dorsal vein of penis > internal pudendal vein > prostatic venous plexus > internal iliac vein. II. Posterior urethra is drained into prostatic and vesical venous plexus > internal iliac vein. D. Nerve supply : Most of the urethra is supplied by nerves of the autonomous nervous system. a. They are terminal part by somatic nerves. I. Sympathetic fibres are derived from the superior hypogastric plexus; the preganglionic fibres arise from L1 and L2 segments. II Parasympathetic fibres are derived from pelvic splanchnic nerves, carrying pre-ganglionic fibres from S2, S3 and S4 segments. III. Somatic fibres are derived from the urethral branches of the pudendal nerves.

3 Abdomen

I. Inferior vesical, branch of anterior trunk of internal iliac artery. II. Middle rectal, branch of anterior trunk of internal iliac artery. It supplies pelvic part of urethra. III. Internal pudendal, smaller terminal branch of anterior trunk of internal iliac artery. IV. Urethral branch, a branch of artery of penis (branch of internal pudendal artery.

328

Exam-Oriented Anatomy

E. Lymphatic drainage : a. The lymphatics from prostatic and membranous parts drain into internal and external iliac lymph nodes. b. The lymphatics from spongy part drains into deep inguinal and sometimes into external iliac lymph nodes. 2. Histology : It presents three coats from outside inward. A. Muscular coat a. The prostatic urethra shows mainly longitudinal muscle. b. Rest of the urethra demonstrates inner longitudinal and outer circular layers of the smooth muscle B. Submucous coat consists of erectile vascular tissue. C. Mucous membrane presents regional variation. a. Above the colliculus: It is lined by transitional epithelium. b. Between the colliculus and the terminal fossa: It is lined by stratified columnar epithelium. c. Distal to terminal fossa: It is lined by stratified squamous non-keratinized epithelium. 3. Development A. Chronological age: It develops at the end of 3rd month of intrauterine life.

Abdomen

3

B. Germ layer a. Endoderm, b. Ectoderm, and c. Mesoderm. C. Sources a. Prostatic part. It is discussed as above and below the opening of ejaculatory duct. b. Above the opening of ejaculatory duct: The walls are developed from various sources. c. Anterior and lateral wall develops from caudal part of vesicourethral canal. It is of endoderm in origin. d. Posterior wall develops from absorbed part of mesonephric duct. It is mesoderm in origin. D. Below, the opening of ejaculatory duct develops from pelvic part of definitive urogenital sinus. It develops endoderm in origin. a. Membranous part develops from pelvic part of definitive urogenital sinus. It is endodermal in origin. b. Penile part develops from phallic part of definitive urogenital sinus, which is endodermal in origin c. Terminal part develops from ectoderm.

Urinary Bladder and Urethra

329

E. Anomalies a. Hypospadias: The urethra opens anywhere on the undersurface of the penis. b. Epispadias: The urethra opens on dorsal surface of penis close to anterior abdominal wall. c. Ectopia vesicae: There is deficient infraumbilical part of anterior abdominal wall. 4. Applied anatomy ¾ Catheterization: A rubber or metallic tube is passed into the bladder through the urethral meatus. It is done to drain the urine in retention of bladder. It is important to keep in mind the normal curvatures of urethra while catheterization. The forceful insertion of metallic instruments may create false passage in the urethra. ¾ Rupture of the urethra is common beneath the pubis. It is usually fall on sharp object. This causes extravasation of urine. • Rupture of urethra, superficial to perineal membrane, results in extravasation of urine in superficial perineal pouch. The urine accumulates in scrotum > penis > anterior abdominal wall deep to fascia of Scarpa. It may extend up to umbilicus. • Rupture of urethra, deep to perineal membrane, produces extravasation of urine in the extraperitoneal space. It accumulates in the anterior abdominal wall superficial to peritoneum. ¾ Urethritis is an inflammation of urethra.

Abdomen

3

26 Female Reproductive Organs

OLA-45 Prolapse of uterus

1. Definition: Falling down of uterus or sinking of uterus is called prolapse of uterus. 2. Types of prolapse: Prolapse of uterus with prolapse of A. Urinary bladder is called cystocoele. B. Urethra is called urethrocoele. C. Rectum is called rectocoele. D. Procidentia: Falling down the cervix through vagina is called procidentia. SN-67

Prolapse of uterus

1. Definition: It is downward displacement of uterus from the normal position. 2. Degree of prolapse: Depending upon the extent of displacement of uterus, it is described as (Fig. 26.1) A. First degree: The cervix is within the vaginal orifice. B. Second degree: The cervix is outside the orifice and up to the level of vulva. C. Third degree: The entire uterus is outside the orifice. D. Procidentia: Whole uterus is outside the vaginal orifice.

Fig. 26.1: Degree of prolapse of uterus 330

Female

Reproductive Organs

331

3. Causes A. Injury to the perineal body is one of the commonest causes of prolapse of uterus. The situation is exacerbated in the presence of a a. Disrupted perineal body or with b. Atrophic pelvic floor. B. Predisposing factors a. Retroversion uterus, b. Loss of tone of the muscles of pelvic diaphragm, c. Perineal tears, and d. Repeated childbirth 4. Types of prolapse: Please Refer OLA-45. LAQ-29 Describe ovary under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

It is a female

reproductive glands, situated in the

gonad which forms the ova.

1. Gross anatomy A. Situation: It is located in ovarian fossa. B. Dimension: 3 × 1.5 × 1 cm (length x breadth x thickness). C. External features a. Surfaces I. Medial, and II. Lateral. b. Borders I. Anterior or mesovarian border, and II. Posterior border is free border. c. Poles I. Upper broader, II. Lower narrower, and III. Axis i. Multiparous: Horizontal. ii. Nulliparous: Vertical.

3 Abdomen

Introduction: The ovaries are a pair of female lesser pelvis.

332

Exam-Oriented Anatomy

D. Relations (Figs 26.2 and 26.3) a. Peritoneal I. Ovary is entirely covered with peritoneum except along the mesovarian border, i.e. anterior border where peritoneum is continuous with the posterior layer of broad ligament. II. Suspensory ligament of the ovary: It extends from upper pole of ovary to external iliac vessels. It contains ovarian vessels. b. Visceral I. Upper pole is related to uterine tube and external iliac veins. II. Lower pole is related to pelvic floor. III. Anterior border is related to uterine tube and obliterated umbilical artery. IV. Posterior border i. Uterine tube ii. Ureter. V. Lateral surface: Ovarian fossa is related to obturator vessels and obturator nerve is separated by peritoneum, which is lined by parietal peritoneum. VI. Medial surface: Uterine tubes.

Abdomen

3

Fig. 26.2: Relations of anterior and posterior borders and peritoneal reflection of right ovary

E. Blood supply a. Arterial supply : The ovary is supplied by the ovarian artery. It is a branch of the abdominal aorta arising just below the renal artery. The artery runs down behind the peritoneum. It crosses the ureter obliquely and crosses the brim of the pelvis. It enters the suspensory ligament. It gives a branch to the uterine

Female

Reproductive Organs

333

Fig. 26.3: Relations of upper pole, lower pole and medial surface of right ovary

tube which runs between the two layers of the broad ligament. It anastomoses with the uterine artery. b. Venous drainage : The ovarian veins form a plexus in the mesovarian and the suspensory ligament which is called pampiniform plexus. The plexus drains into a pair of ovarian veins which accompany the ovarian artery. They usually combine as a single trunk before their termination. Right ovarian vein opens into the inferior vena cava. Left ovarian vein opens into left renal vein.

G. Lymphatic drainage : The lymphatics of the ovary drain to para-aortic nodes alongside the origin of ovarian artery. 2. Histology : It shows following layers from inside out (Fig. 26.4). A. Simple cuboidal epithelium. B. Tunica albuginea, a thin layer of connective tissue. C. The cortex contains ovarian follicles at various stages of development. Each follicle contains one oocyte. One follicle matures every month and sheds an oocyte. There are 400 oocytes that are ovulated in the reproductive life. After the oocyte is liberated, the Graafian follicle is converted into a structure called the corpus luteum.

3 Abdomen

F. Nerve supply : It is formed by ovarian plexus. The fibres of the plexus are formed by a. Sympathetic fibres reach the ovary from the aortic plexus. The fibres run along its blood vessels. The pre-ganglionic fibres arise from T10 and T11 segments of the spinal cord. They are vasoconstrictors. b. Parasympathetic fibres may reach the ovary from the inferior hypogastric plexus via uterine artery. c. Sensory fibres accompany the sympathetic nerves so that the ovarian pain may be referred along the umbilicus.

334

Exam-Oriented Anatomy

Fig. 26.4: Histology of ovary

Abdomen

3

3. Development A. Chronological age: It develops in the 7th week of intrauterine life. B. Germ layer: Endoderm. C. Site: Wall of the yolk sac close to the allantois. D. Sources a. Ovary develops from the coelomic epithelium lining the medial side of the nephrogenic cord. gonad forms cortical cords. In the 4th b. The surface epithelium of the female month of intrauterine life, these cords form primitive germ cell. c. Descend of the gonads is considerably less in the female The ovary is settled just below the rim of the true pelvis.

than male

.

4. Applied anatomy ¾ Prolapse of ovaries: It is frequently displaced in the pouch of Douglas. It can be palpated by per vaginal examination. ¾ The carcinoma of ovary is common, and accounts for 15% of all cancers and 20% of gynaecological cancers. ¾ Krukenberg’s tumour: It is transcoelomic migration of cancer cells from mammary gland to ovary and forms a tumour called Krukenberg’s tumour. ¾ Oophoritis: It is the inflammation of ovary. It may produce localized peritonitis of the ovarian fossa and eventual irritation of the obturator nerve. This results into pain on the medial side of thigh.

Female

Reproductive Organs

335

SAQ-10 Ovarian fossa

Introduction: It is a fossa present in the pelvis which contains ovary, the female gonad. 1. Boundaries: It is bounded (Fig. 26.5) A. Anteriorly by obliterated umbilical artery. B. Posteriorly a. Ureter, and b. Internal iliac artery

Fig. 26.5: Boundaries of the ovarian fossa

2. Applied anatomy : The relations of the obturator nerve to the ovarian fossa needs to be remembered. The lateral surface of the ovary is in contact with the parietal peritoneum of ovarian fossa. The obturator nerve and vessels are retroperitoneal structures in this location. Inflammation of ovary may produce localized peritonitis in the ovarian fossa. It causes irritation of the obturator nerve. The patient may experience pain along the medial side of thigh and knee. LAQ-30 Describe uterine tube under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Abdomen

3

336

Exam-Oriented Anatomy

Introduction: These are the tortuous ducts which convey the ova from the ovary to the uterus. The spermatozoa introduced into the vagina pass into the uterus and then into the uterine tubes. The fertilization usually takes place in the ampullary part of the fallopian tube. Length: About 10 cm (4”). 1. Gross anatomy A. External features: Parts of uterine tube are as follows a. Infundibulum: It is a funnel

finger-like processes called fimbriae. It is, therefore, called fimbriated end. One of the fimbriae is longer than the others and is attached to be tubal pole of the ovary. It is known as ovarian fimbriae. At the lateral end, the uterine tube opens into the peritoneal cavity through its abdominal ostium. It is about 3 mm in diameter. b. Ampulla: It is thin-walled, dilated and tortuous part of fallopian tube. It forms approximately lateral two-thirds of the tube. It is about 4 mm in diameter. c. Isthmus: It is narrow, rounded and cord-like. d. The interstitial part of tube is about 1 cm long and lies within the wall. B. Course and relations (Fig. 26.6) a. The ampulla arches over the ovary and is related to the anterior and posterior borders of the ovary. It is also related to upper pole and medial surface of the ovary. b. The uterine tube lies in the upper free margin of the broad ligament of uterus. The part of the broad ligament between the attachment of the mesovarian and the uterine tube is known as mesosalpinx.

Abdomen

3

shaped lateral end of uterine tube. It bears

Fig. 26.6: The parts, relations and blood supply of the uterine tube

C. Blood supply a. Arterial supply : The uterine tube is supplied by I. Tubal branch of ovarian artery. The tubal artery runs below the tube between the layers of the broad ligament. It anastomoses with the tubal branches of uterine artery in the broad ligament. II. Tubal branch of uterine artery.

Female

Reproductive Organs

337

b. Venous drainage : The veins run parallel with the arteries. The veins of the tube join the pampiniform plexus and drain into the uterine veins. D. Nerve supply : The uterine tubes are supplied by both the sympathetic and parasympathetic nerves. a. The sympathetic fibres are derived from the hypogastric plexuses. They are vasomotor in function. b. Parasympathetic fibres are derived from S2, S3, S4. They inhibit peristalsis and produce vasodilatation. E. Lymphatic drainage a. The lymphatics of the fallopian tube join the lymphatics of the ovary and drain into lateral aortic and para-aortic nodes. b. The lymphatics from the isthmus accompany the round ligament of the uterus and drain into the superficial inguinal nodes. 2. Histology : It consists of (Fig. 26.7) A. Muscular coat: It consists of inner circular and outer longitudinal layers of the smooth muscle. B. The mucous membrane shows numerous branching fold which fill the lumen of the tube. C. Mucosa: It is lined by ciliated columnar epithelium.

Abdomen

3

Fig. 26.7: Histology of uterine tube

338

Exam-Oriented Anatomy

3. Development A. Chronological age: It develops in the 8th week of intrauterine life. B. Germ layer: Mesoderm. C. Site: Intermediate mesoderm. D. Sources a. Proximal unfused vertical part of the paramesonephric duct forms the fallopian tube. b. Fimbriae are formed from the invagination of the paramesonephric duct into the coelomic epithelium. E. Anomalies a. Absence of the uterine tubes on one or both the sides. b. The tubes may be partially or completely duplicated on one or both the sides. c. There may be atresia of the tubes. d. Hydatid (of Morgagni): The cranial end of the paramesonephric duct does not contribute to the infundibulum of the uterine tube. It may persist as a vesicular appendage called hydatid of Morgagni. 4. Applied anatomy

Abdomen

3

¾ Salpingitis: Inflammation of the uterine tube is called salpingitis. ¾ Tubectomy: It is removing a segment of uterine tube on both sides. This is done in family planning operation. It can be done by laparoscopy or through an incision in abdominal wall. ¾ Sterility: Inability to conceive or induce conception is called sterility. The most common cause of sterility in the female is blockage of the fallopian tube. It may be congenital or may be acquired by tuberculosis infection. The patency of the tube is investigated by • Chromopertubation: It is a method for study of patency of fallopian tube in suspected infertility in women. It is currently one of the standard procedures in the field. ¾ Hysterosalpingography: It is a radiological technique. A radio-opaque oily dye is injected into the uterus through the cannula. It helps to visualize the cavity of the uterus and the lumina of the tubes. It helps to find out the patency of tubes. OLA-46 What is hysterosalpingography?

Hysterosalpingography: It is a radiological technique. A radio-opaque oily dye is injected into the LAQ through the cannula. It helps to visualize the cavity of the uterus and the lumen of the tubes. It helps to find out the patency of tubes. SN-68

Applied importance of supports of uterus.

1. Supports of uterus keep the uterus in position. Weakness of the supports results in prolapse of uterus. Please refer LAQ-31/1-A-b pg-341.

Female

Reproductive Organs

339

OLA-47 Abnormal positions of uterus

1. Dextrorotation of the fundus: Uterus lies in the median plane. It is twisted in the long axis either to the right or left. 2. Levo (left) rotation: Cervix is tilted more to the left side and comes closer to left ureter. A. Dextrorotation and levorotation take place in anteroposterior axis which passes through internal os. Broad ligament of uterus

1. It is fold of peritoneum extending from body of uterus to the lateral pelvic wall. It has A. Two layers a. Anterior and posterior layers. B. Margns a. Lateral and b. Superior free margins. 2. Structures in broad ligament and their position in the broad ligament. A. Fibrofatty tissue between two layers is called parametrium. It is most abundant near the cervix and vagina. B. Fallopian tube in upper free margin. C. Round ligament of uterus is present in anterior inferior part of broad ligament. D. Ligament of ovary is present in posterior inferior part of broad ligament. E. Uterine artery ascends between two layers of broad ligament. F. Ovarian vessels, G. Utero-vaginal and ovarian nerve plexus. H. Lymph nodes and lymph vessels I. Remnants of Wolffian duct or mesonephric duct a. Epoophoron, b. Paroophoron, and c. Gartner’s duct.

Fig. 26.8: Broad ligament of uterus

3 Abdomen

SN-69

340

Exam-Oriented Anatomy

Not but yes content of broad ligament—Tip Box 26.1 Note: Anatomically, the ureters are not content of broad ligament. In growing tumours, they may be pushed and can be contents of broad ligament. 3. Parts of broad ligament A. Mesosalpinx: Part of broad ligament between uterine tube and mesovarian. B. Mesovarian: Ovary is attached to posterior layer of broad ligament. LAQ-31 Describe uterus under following heads 1. Gross anatomy, 2. Histology, 3. Development, and 4. Applied anatomy.

Introduction: It is a child-bearing organ present in the pelvic cavity.

Abdomen

3

Fig. 26.9: Peritoneal reflection over pelvic organs in female

1. Gross anatomy A. External features a. Axis of uterus (Fig. 26.10) I. Anteversion (ante—prior to or in front of, version—relation of uterus with the vagina around transverse axis through external os of cervix): It is the forward lipping or tilting of an organ. It is the displacement of the organ. It is tipped forward but not bend at an angle as occurs in anteflexion. However, it is defined as forward angle between the axis of cervix and that of vagina, measuring 90°.

Female

Reproductive Organs

341

Fig. 26.10: Anteflexion and anteversion of the uterus

i. It is a pyramidal shaped fibromuscular node and is formed by paired and unpaired muscles. ii. Functions: It maintains the integrity of the pelvic floor. III. Muscles i. Levator ani which is formed by • Pubovaginalis, and • Puborectal sling. ii. Functions of levator ani • It constricts the vagina from the side and maintains the anorectal flexure. • It prevents the prolapse of the uterus. • In damaged puborectal sling, the anorectal angulation becomes straight and this results into prolapse of the rectum. IV. Ligaments: These are minor supports. i. Mackendrodt’s ligament: It keeps the cervix in the midline. It prevents the downward displacement of uterus through vagina. ii. Uterosacral ligament: It is condensation of pelvic fascia that extends from cervix. It embraces the rectouterine pouch and attaches to the fascia over piriformis. It is best palpated in rectal examination. It keeps the

3 Abdomen

II. Anteflexion: Forward angle between the body and the cervix, at the isthmus. It measures 135°, provided bladder and rectum are empty. b. Supports of uterus: The most fixed part of the uterus is cervix. The urinary bladder, and vagina maintain the position of the uterus, e.g. distention of the bladder makes the uterus erect and lies with the same line with vagina. This position favours prolapse of the uterus. Following are the main supports. I. Axis: The maintenance of the anteversion axis is an important pre-requisite for the support of uterus. II. Perineal body

342

Exam-Oriented Anatomy

cervix braced backward against the forward pool of the round ligaments on the fundus and so, maintain the body of uterus in ante-version. iii. Pubocervical ligament: It prevents excessive traction of cervix by counter acting uterosacral ligament. It keeps the cervix in position. Refer Fig. 26.8: Broad ligaments of uterus V. Tone of the muscles of the abdominal wall maintains intra-abdominal pressure. In weakness of the muscle tone, sigmoid colon and small intestine exert pressure upon the uterus. Know what is not—Important Box 26.2 Note: Peritoneal folds do not play role in maintaining support of the uterus. B. Blood supply a. Arterial supply : It is chiefly by uterine arteries, which are branches of anterior division of internal iliac artery. They are tortuous in course for the expansion of the uterus during pregnancy. They give > arcuate artery > radial artery > spiral artey > basilar artey.

Abdomen

3

b. Venous drainage : The veins of the uterus form a plexus along the lateral border of the uterus. The plexus drains through the uterine, ovarian and vaginal veins into the internal iliac veins> common iliac > inferior vena cava. C. Nerve supply : The uterus is richly supplied by both sympathetic and parasympathetic nerves, through the inferior hypogastric and ovarian plexuses. a. Sympathetic nerves (T12, L1) produce uterine contraction and vasoconstriction. b. Parasympathetic nerves (S2, S3, S4) produce uterine inhibition and vasodilatation. However, these effects are complicated by the pronounced effects of hormones on the genital tract. Pain sensations from the I. Body of the uterus pass along the sympathetic nerves. II. Cervix, pass along the parasympathetic nerves. D. Lymphatic drainage : The lymphatics pass with each vein to the internal iliac group of lymph nodes. The lymphatics of the uterus forms three intercommunicating networks: Endometrial, myometrial and subperitoneal. These plexuses drain into lymphatics on the side of uterus. The lymphatics of the uterus are displayed in Fig. 26.11 and Table 26.1. 2. Histology : The uterus consists of (Figs 26.12 and 26.13) A. Endometrium: a. The mucous membrane of the uterus is called endometrium. b. It is lined by the simple columnar epithelium. c. It rests on the connective tissue.

Reproductive Organs

343

Fig. 26.11: Lymphatic drainage of the uterus Table 26.1: Lymphatic drainage of the uterus

d. It shows numerous tubular glands which are dipped into the stroma. e. The appearance of the endometrium varies depending upon the phase of the menstrual cycle. f. In the proliferative phase, the endometrium is relatively thin and the glands are straight.

3 Abdomen

Female

344

Exam-Oriented Anatomy

g. In the secretory phase, the endometrium is much thick. The uterine glands are long dilated and tortuous. They show saw-toothed margin in the section. The blood vessels are more conspicuous. h. The stroma is divisible into three parts. I. The superficial layer is called stratum compactum in which the cells are closely packed.

Abdomen

3 Fig. 26.12: Histology of uterus—proliferative phase

Fig. 26.13: Section of uterus—secretory phase

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345

II. Middle stratum spongiosum, which is relatively loose. III. Stratum basale in which the cells are densely packed. B. Myometrium a. Middle thick layer is formed by smooth muscles. It is called myometrium. b. It consists of various layers. But these are difficult to make out as fibres running in various directions. C. Perimetrium: Outer layer is perimetrium. 3. Development A. Chronological age: It develops in the 8th week of intrauterine life. B. Germ layer: Mesoderm. C. Site: Intermediate mesoderm. D. Sources a. Epithelium of the uterus develops from the fused paramesonephric ducts. b. The myometrium is derived from the surrounding mesoderm. c. The caudal unfused part partially gets embedded within the substance and forms fundus of the uterus. E. Anomalies a. Common anomaly I. Uterus bicornuate: It is one of the relatively common anomalies of the uterus. II. The uterus has two horns entering a common vagina. b. The less common anomalies are I. The lumen may be partially or completely subdivided by a septum. II. The entire uterus may be absent. III. One-half of the uterus may be absent (unicornuate uterus). IV. The uterus may remain rudimentary. V. There may be atresia of the lumen either in the body or in the cervix. VI. The cervix may be absent. 4. Applied anatomy ¾ Sometimes the uterus passes downwards into the vagina which is called prolapse of the uterus. It is caused by the weakness of the various supports of uterus. ¾ Hysterectomy is the operation for the removal of the uterus. ¾ Insertion of a foreign body into the uterus can prevent implantation of a fertilized ovum. This is the basic principle underlying the use of various intrauterine contraceptive devices. ¾ Caesarean section: The delivery of the child is done by opening the abdomen and uterus. It is commonly done for the cephalopelvic disproportion. SN-70

Uterine artery

Introduction: Uterine artery is present only in females . It is the chief artery of the uterus. It is homologous to the artery to the ductus deferens in males .

3 Abdomen

Female

346

Exam-Oriented Anatomy

1. Origin: It is a large artery which springs from anterior division of the internal iliac artery below the obturator artery. 2. Course and relations (Fig. 26.14) A. It has a C-shaped course in the pelvis. B. It is directed downwards and medially on the levator ani muscles and crosses the ureter. The points at this site are as follows a. This is the most dangerous site. b. Ureter is likely to damge during hysterectomy because of the following reasons. I. Uteine artery crosses from lateral to medial. II. Uterine artery crosses ureter from front. It is described as “water under the bridge” by surgeons. In this simile, water is the ureter and bridge represent uterine tube. However, author feels it is better to call it as ‘Urine tube under blood tube’. III. It is 1" lateral to the cervix. IV. It is above the Mackendrodt’s ligament. c. It runs along the lateral border of the body. d. It runs in a very tortuous manner, lying between the two layers of the broad ligament. 3. Branches: Close to the area of crossing, the artery gives (Fig. 26.14)

Abdomen

3

A. Ureteric, B. Vaginal, and C. Cervical branches. The cervical branches form circular anastomosis around the isthmus. D. On reaching the side of cervix, the uterine artery divides into two branches. a. A smaller descending vaginal branch, supplies the cervix and vagina. b. A larger ascending branch runs along the lateral margin of the uterus. E. Along the fallopian tube, it gives off tubal branches and a few ovarian twigs. F. The ascending branch gives a series of arcuate or coronary arteries. They run transversely on the anterior and posterior surfaces of the body of uterus. G. The branches of the two sides anastomose with their counterparts in the midline. H. Numerous radial arteries arise from the coronary arteries. They pierce the myometrium centripetally and anastomose with each other to form stratum vasculare in the middle layer of muscular coat. I. From stratum vasculare, two sets of branches—basal and spiral—arise to supply the endometrium. J. The functional zone of the endometrium is cast off during menstruation and is supplied by the spiral arteries. Whereas the basal zone of the endometrium helps in the regeneration of the denuded endometrium and is supplied by basal arteries.

Female

Reproductive Organs

347

Fig. 26.14: Course and branches of the uterine artery

Dil Mange more—Tip

4. Distribution: The uterine artery supplies A. Ureter, B. Vagina, C. Uterus, D. Medial two-thirds of uterine tube, E. Ovary, and F. Structures within the broad ligament, i.e. a. Round ligament of the uterus, and b. Ligament of the ovary. Additional responsibility Box 26.4 Please note that it also supplies the placenta during pregnancy.

3 Abdomen

Box 26.3 Please note important additional information about the uterine artery. • Uterine artery is one of the tortuous arteries in the body. • It hypertrophies, i.e. greatly enlarged during pregnancy. • Muscular branches to the uterine muscle are also tortuous and are known as helicine arteries. • The muscle bundles in myometrium layer are arranged in a figure-8 design and hence on their contraction blood vessels are clamped. • This is the reason why these muscle fibres are known as living ligatures of the uterus.

348

Exam-Oriented Anatomy

5. Anastomosis: Uterine artery forms anastomosis with A. Vaginal artery, it forms two trunks in front and behind the vagina. They are known as azygos arteries of the vagina. B. Cervical branches form circular anastomosis around the isthmus. C. Fellow of the opposite side on the body of uterus. D. Ovarian artery at medial end of the uterine tube. 6. Applied anatomy ¾ The branches of uterine artery diminish rapidly in size as they pass toward the uterine cavity. Hence, there is relatively little bleeding in a midline section of the uterus. ¾ It is essential to know that the ureter is identified at the base of the broad ligament. ¾ The uterine artery crosses ureter approximately 2 cm superior to the ischial spine. The ureter is in danger of being inadvertently clamped during hysterectomy. Hence, care should be taken not to injure the ureter during ligation of the uterine artery. ¾ In cases of dextrorotation of the fundus, the cervix is tilted more to the left side and becomes closer to the left ureter. Hence, one should be more cautious while ligating the left uterine artery. SN-71

Abdomen

3

Middle rectal artery

1. Middle rectal artery is characterized by the following features A. It is known for its variation in presence, origin, size and distribution. B. It is often absent, multiple or may be small. , it may be replaced by a branch from the inferior vesical artery. C. In males D. In females

, it may be replaced by a branch from the uterine or vaginal artery.

2. Origin: It arises from internal iliac artery. The origin is close to inferior vesical artery (Figs 26.15 and 26.16). 3. Course (Figs 26.15 and 26.16) A. It runs into the lateral fascial coverings of the mesorectum. It anastomoses freely with the arteries of the opposite sides. B. It has poor anastomosis with the a. Superior rectal artery, which is a continuation of inferior mesenteric artery, and b. Inferior rectal artery, a branch of internal pudendal artery. 4. Distribution A. In males , it mainly supplies the (Fig. 26.15) a. Seminal vesicles, b. Vas deferens, and the c. Prostate B. In females

, it supplies the vagina (Fig. 26.16).

Female

Reproductive Organs

349

Fig. 26.15: Origin, course and branches of middle rectal artery in male

C. In males

and females

, it supplies

3 Abdomen

a. Only muscle coat of middle 1/3rd of the outer coats of rectum, b. Mucous membrane of anal canal, and c. Muscle of the upper part of anal canal.

Fig. 26.16: Origin, course and branches of middle rectal artery in female

27 Male

Reproductive Organs

OLA-48 Median lobe of prostate

Median or middle lobe 1. It lies behind the upper part of urethra and is present in front of the ejaculatory duct. 2. It is closely related to neck of urinary bladder. 3. It produces an elevation in the lower part of trigone of the bladder, known as the uvula vesicae. LAQ-32 Describe prostate under following heads 1. Gross anatomy, 2. Histology, 3. Age changes, and 4. Applied anatomy.

Introduction: It is a fibromusculoglandular organ. It has fibrous, muscular and glandular parts. It is an accessory organ of male reproductive system. It adds 30% of bulk to the seminal fluid. There is no counterpart in the female

.

1. Gross anatomy A. Situation: It is situated in the lesser pelvis. B. Dimension: Breadth is more than the length. a. Anteroposterior: 2 cm. b. Vertical: 3 cm. c. Transverse: 4 cm. d. Weight: 8 g (The word “prostate” has 8 letters which is equal to the weight.) e. Shape: It resembles inverted cone 350

.

Male

Reproductive Organs

351

C. External features a. It has a base, an apex and three surfaces. The surfaces are I. Anterior, II. Posterior, and III. Inferolateral. b. Base is fused with the neck of bladder. Apex is blunt. The urethra travels from base to apex. It is called prostatic part of urethra. It continues as membranous urethra. c. Consistency: It is firm in consistency and is formed by fibromuscular stroma. d. Lobes (Figs 27.1 and 27.2): It has five lobes I. Anterior lobe (Absence of glandular tissue): It is present in front of prostatic urethra. There is no glandular tissue in anterior lobe. II. Posterior lobe: It is the part of the prostate present behind the prostatic urethra and connects two lateral lobes. It is a common site of beginning of Primary carcinoma. III. Median or Middle lobe: It lies behind the upper part of urethra and is present in front of the ejaculatory duct. It is closely related to neck of urinary

Abdomen

3 Fig. 27.1: Sagittal section of bladder and prostate showing lobes of prostate

Fig. 27.2: Lobes of the prostate gland

352

Exam-Oriented Anatomy

bladder. It produces an elevation in the lower part of trigone of the bladder, known as the uvula vesicae. Middle-aged tumour arises from Median lobe. IV. Lateral lobes lie one on each side of urethra. e. Capsules: It has anatomical and pathological capsules. I. Anatomical i. True capsule: It is condensation of the fibrous connective tissue around the peripheral part of the gland. It contains no venous plexus. ii. False capsule: It lies outside the true capsule and is derived from the pelvic fascia. The prostatic venous plexus is embedded in it. Posteriorly, it is a vascular and is formed by the rectovesical fascia of Denonvilliers) prostate-peritoneal fascia). II. Pathological: In benign prostatic hyperplasia, the peripheral part of the gland gets compressed and is called pathological capsule. f. Structures within prostate: The prostatic urethra is present at the junction of anterior one-third and posterior two-thirds of prostate. I. The prostatic utricle is a blind sac, one end of which opens into the urethra. II. The ejaculatory ducts open into the prostatic urethra on each side of the opening of the prostatic utricles. D. Relations: Visceral relations (Figs 27.3 and 27.4)

Abdomen

3

a. Anteriorly I. Retropubic space, and II. Pubic symphysis. b. Superiorly: Neck of urinary bladder. c. Posteriorly: Rectum. d. Inferiorly: Urogenital diaphragm and pelvic diaphragm. e. Laterally: It is clasped by levator prostate.

Fig. 27.3: Relations of urinary bladder and prostate (from behind)

Male

Reproductive Organs

353

Fig. 27.4: Relations of the prostate

E. Blood supply a. Arterial supply : The prostate is supplied by

b. Venous drainage : I. The veins form a rich plexus around the sides and the base of the gland. They lie between true and false capsules. II. The plexus receives the deep dorsal vein of the penis. III. It communicates with the vesical plexus and forms vesicoprostatic plexus. It is situated between the bladder and prostate. IV. There are no valves in these veins. There is a free communication between the prostatic and vertebral venous plexuses. The malignant cells of the prostate spreads to vertebral column, skull and central nervous system. F. Nerve supply a. Sympathetic nerve is derived from inferior hypogastric plexus. b. Parasympathetic nerve is derived from pelvic splanchnic nerve. I. It contains thick nerves and numerous large ganglia. II. The plexus contains sympathetic and parasympathetic nerves. III. The secretions of the prostate are produced by sympathetic and discharged by parasympathetic nerve (pelvic splanchnic nerve). G. Lymphatic drainage : The lymphatics of the prostate pass across the pelvic floor to the nodes on the side wall of the pelvis. They pass along the internal iliac vessels. They mainly drain into

3 Abdomen

I. Prostatic branch of inferior vesical artery which is the main artery of the prostate. II. Small branches of i. Middle rectal artery. ii. Internal pudendal arteries. iii. Branches of these arteries form two plexuses • A large outer or subcapsular plexus, and • Small inner or periurethral plexus. The greater part of the gland is supplied by the subcapsular plexus.

354

Exam-Oriented Anatomy

a. Internal iliac lymph node, and b. Sacral group of lymph nodes 2. Histology : It is a fibromuscular glandular tissue (Fig. 27.5). It contains A. Fibrous stroma, B. Smooth muscle, and C. The acini of varying shapes and sizes. It contains large cavities which are lined by columnar epithelium. There is infoldings of the epithelium which is a distinguishing feature. It is divided into I. Outer larger zone: It contains large branched glands with ducts which curve backwards and opens into prostatic utricle. II. Inner smaller zone: It contains i. Submucous glands opening in prostatic sinuses. ii. Simple mucosal glands thrown into folds. D. Small rounded masses of uniform or laminated structures are found within the lumen of the follicles. They are called amyloid bodies or corpora amylacea. These are more abundant in older individuals. This consists of condensed glycoprotein. They are often calcified. E. The fibromuscular tissue forms a conspicuous feature of the section of the prostate.

Abdomen

3

Fig. 27.5: Histology of porstate

3. Age changes in prostate A. At birth, prostate is made up mainly of stroma which consists of simple ducts. a. During first 6 weeks, the epithelium of the duct and of the prostatic utricle undergoes hyperplasia and squamous metaplasia. b. Between 9 and 14 years, there is a proliferation of duct system and the glands slowly increase in size.

Male

Reproductive Organs

355

B. At puberty: It becomes double in size. The stroma is condensed and markedly reduced. a. From 20 to 30 years, there is a proliferation of glandular elements and the infolding of the glandular epithelium. b. From 30 to 45 years, size remains constant. c. After 45 to 50 years, the prostate is either enlarged or reduced in size. 4. Applied anatomy ¾ Prostatitis: It is an inflammation of the prostate gland. ¾ About tumours of prostate • Benign hypertrophy of prostate (Middle age adenoma) occurs in the Median lobe. It is a local proliferation of the internal zone or central region, the region of mucosal or periurethral gland. • Anterior lobe of prostate has absence of glandular tissue. Hence, benign hypertrophy never occurs in anterior lobe. • The prostate is a common site of carcinoma. It can spread to vertebral column and skull because of communication of prostatic and vertebral venous plexuses. • Primary carcinoma occurs in the peripheral zone (Posterior lobe). The spread of cancer of prostate to rectum is prevented by Denonvilliers’ fascia. ¾ An approach to the prostatectomy • Retropubically: Approach of prostate is from behind the pubis. It is through the prostatic capsule. • Perineal approach: Across the perineum, dissecting in front of rectum and reaching the prostate through Denonvilliers’ fascia. • Transurethral: The obstructed mass of prostatic tissue is removed by operating cystoscope. In transurethral resection, the verumontanum (colliculus seminalis) is an important landmark. The surgeon keeps proximal to this point in order not to damage the urethral sphincter mechanism. • An abdominal suprapubic incision into the retropubic space gives a wide exposure to the organ. ¾ About prostatectomy • Prostatectomy is enucleation of a hyperplastic mass of glandular tissue of the prostate gland. • In performing enucleation of the prostate, the surgeon enters plane between the pathological capsule and true capsule. The tumour is enucleated and a pathological capsule is left behind. The prostatic venous plexus, lying external to the pathological capsule and internal the false capsule, is thus undisturbed. ¾ In chronic obstruction due to an enlarged prostate, the bladder walls show typical trabeculated open weave appearance. It is seen through cystoscope.

3 Abdomen

• Transvesically: Across the bladder

356

Exam-Oriented Anatomy

OLA-49 Benign prostatic hypertrophy

Benign hypertrophy of prostate (middle age adenoma): It occurs in the median lobe. Median lobe surrounds the urethra. There is local proliferation of the internal zone or central region. 1. It occurs in 45 to 50 years of age. 2. It causes retention of urine due to distortion of urethra. Enlargement of the prostate projects into urinary bladder. It acts as a valve over the internal urethral orifice. The blockage is proportionate to strain. More patient strains, more it obstructs the passage. 3. Prostatectomy is done to relieve the symptoms. 4. It is removed through A. Transurethral prostatectomy B. Retropubic prostatectomy C. Perineal prostatectomy

Abdomen

3

28 Rectum and Anal Canal

OLA-50 Prostatic urethra

Introduction Situation: The part of urethra passing through the prostate gland is prostatic urethra. Peculiarities: It is the widest and most dilated part of the male urethra. It is the narrowest at the junction with the membranous urethra. 1. Internal features: Posterior wall of the prostatic urethra shows following features. A. The urethral crest, a median longitudinal ridge of mucous membrane. B. The colliculus seminalis, an elevation on the middle of the urethral crest. C. The prostatic utricle, a blind sac about 6 mm long, which lies within the prostate. D. There is an orifice on the elevation through which prostatic utricle opens into the urethra. E. On each side of this orifice, there are openings of the ejaculatory ducts. F. There are two vertical grooves called prostatic sinuses situated one on each side of urethral crest. G. Each sinus presents the openings of 20 to 30 prostatic glands. OLA-51 Urethral sphincters

1. Proximal (internal) urethral sphincter A. It is formed by condensation of intermediate circular fibres of urinary bladder. B. It is involuntary. It is supplied by autonomous nerves. They are derived from vesical plexus. C. It is damaged in men in following situations. a. Bladder neck surgery b. Transurethral resection of prostate D. Functions: It may maintain continence when external sphincter has damaged. 2. Distal (external) urethral sphincter: It is also called sphincter urethrae membranacea. 357

358

Exam-Oriented Anatomy

A. Components a. Urethral smooth muscle b. Urethral striated muscle (of rhabdosphincter). It is most important component as it is capable of sustained contractions. c. Pubourethral part of levator ani. d. It is inserted into perineal body. B. Situation: Deep perineal pouch. C. Nerve supply : It is voluntary and supplied by perineal branch of pudendal nerve. OLA-52 Internal anal sphincter

1. It is involuntary in nature. 2. It is local condensation of circular muscle coat. 3. It surrounds the upper 3/4th, i.e. 30 mm of the anal canal. 4. It extends from the upper end of the canal to the white line of Hilton. SN-72

Anal sphincters Table 28.1: Anal sphincters—external and internal

Abdomen

3

Features

External anal sphincter

Internal anal sphincter

• Nature

• Voluntary

• Involuntary

• Type of muscle fibres

• Skeletal muscle

• Local condensation of inner circular muscle

• Situation

• Whole of anal canal

• Upper 3/4th of anal canal

• Extent

• Upper border of anal column to the skin

• From the upper end of the canal to the white line of Hilton

• Parts

• Subcutaneous • Superficial • Deep

• Nerve supply

• Pudendal (somatic) nerve

• Sympathetic and parasympathetic nerves

OLA-53 Mucosal folds of rectum Table 28.2: Two types of folds: Longitudinal and transverse Folds

Longitudinal

Transverse

• Synonymous —

• Horizontal fold or Houston’s valves or plicae transversales recti (Fig. 28.1)

• Site

• Fold

• Projects

• Distance

• 1st transverse

• From right wall

• 12–14 cm above anal canal

• Lower part of empty rectum

Contd.

359

Rectum and Anal Canal

Table 28.2: Two types of folds: Longitudinal and transverse (Contd.) Folds

• Visible

Longitudinal

Transverse

• Empty

• 2nd transverse • Upper end of rectum

• 7.5 cm above anus

• 3rd transverse • Anterior and right walls

• Upper end of rectal ampulla

• 4th transverse • From left wall

• 2.5 cm below middle fold

• Distended rectum

• Nature of fold • Transitory

• Permanent

Fig. 28.1: Valves of Houston

1. Gross anatomy, 2. Development, and 3. Applied anatomy.

Introduction: It is the distal part of hindgut and is present between sigmoid colon and anal canal. 1. Gross anatomy A. Situation: It is situated in the posterior part of lesser pelvis. It lies in front of lower three pieces of sacrum and the coccyx. It begins as a continuation of the sigmoid colon at the level of vertebra S3. It ends by becoming continuous with the anal canal. B. Length: 12 cm. C. External features a. Course and direction: It lies in the median plane. It shows two types of curvature in its course (Fig. 28.2). I. One curvature is in the beginning and other at the end. II. Two anteroposterior curves i. The sacral flexure of the rectum follows the concavity of the sacrum and coccyx.

3 Abdomen

LAQ-33 Describe rectum under following heads

360

Exam-Oriented Anatomy

ii. The perineal flexure of the rectum is the backward bend at the anorectal junction. iii. Three lateral curves. • Upper lateral curve is convex to the right. • Middle lateral curve is convex to the left and is most prominent. • Lower lateral curve is convex to the right.

Fig. 28.2: Curvatures of rectum

Abdomen

3

D. Relations a. Peritoneal relations I. In upper one-third, the peritoneum covers the anterior and lateral surfaces of the rectum. II. In the middle one-third, the peritoneum covers only anterior surface. III. In the lower one-third, there is no peritoneum. b. Visceral relations I. Anteriorly i. Male • Upper two-thirds * Coils of intestine pros * Rectovesical pouch that contains sigmoid colon. • Lower one-third * Urinary bladder, * Terminal part of the ureters, * Seminal vesicles, * Ductus deferens, and * Prostate. Ref. Fig. 25.3

361

Rectum and Anal Canal

ii. Female • Upper two-thirds: Rectouterine pouch containing coils of small intestine. • Lower one-third: Lower part of the vagina. Ref. Fig. 25.4 II. Posterior relations (Fig. 28.3) are same in male

and female

.

3 Abdomen

i. Bones: Lower three pieces of the sacrum, and coccyx ii. Ligament: Anococcygeal ligament. iii. Muscles • Piriformis, • Coccygeus, and • Levator ani. iv. Vessels • Median sacral • Superior rectal, and • Lateral sacral. v. Nerves • Sympathetic chain • Ganglion impar (unpaired) • Anterior primary rami of S3, S4, S5 and • 1st coccygeal nerve, and the pelvic splanchnic nerves, lymph nodes lymphatics and fat.

Fig. 28.3: Posterior relations of rectum

E. Blood supply a. Arterial supply (Fig. 28.4) I. The main blood supply of rectum is by superior rectal artery. It is the continuation of inferior mesenteric artery. II. The muscle wall of the rectum receives from the middle rectal artery which is a branch of internal iliac artery. III. Small branches from the median sacral artery supply the back of the rectum.

362

Exam-Oriented Anatomy

Fig. 28.4: Arterial supply of rectum

Abdomen

3

b. Venous drainage : There is very free anastomosis between the tributaries of the venous system (Fig. 28.5). I. Superior rectal vein: The tributaries of this vein begin in the anal canal. It passes upward in the rectal submucosa. It pierces the muscular coat and unite to form superior rectal vein. It continues upward as inferior mesenteric vein. II. Middle rectal vein: It drains mainly the muscular wall of rectal ampulla. It opens into internal iliac vein. F. Nerve supply : It is supplied through superior rectal and inferior hypogastric plexuses. a. The sympathetic fibres are derived from L1 and L2. These are vasoconstrictor and inhibitory to the rectal musculature and motor to the internal sphincter. b. Parasympathetic fibres are derived from S2, S3 and S4. These are motor to the musculature of rectum and inhibitory to the internal sphincter. I. The sensations of the distension of the rectum are also carried by parasympathetic nerve. II. Pain sensations are carried by both parasympathetic and sympathetic nerves. G. Lymphatic drainage : The lymphatics of the rectum run along the arteries. The lymph vessels in the mucous membrane provide the first filter. The lymphatic vessels pierce the wall of the rectum. a. The lymphatics from more than upper half of the rectum pass along the superior rectal vessels > pararectal and sigmoid nodes > inferior mesenteric nodes.

Rectum and Anal Canal

363

Fig. 28.5: Venous drainage of rectum

3. Applied anatomy ¾ Per rectal examination: The following structures can be palpated by a finger passed per rectum. In male , the posterior surface of prostate, seminal vesical and vasa differentia are palpated. In females , the perineal body and the cervix are palpated.

3 Abdomen

b. The lymphatics from the lower half of the rectum pass along the middle rectal vessels > internal iliac nodes. 2. Development A. Chronological age: It develops in the 4th week of intrauterine life. B. Germ layer: Endoderm and mesoderm. C. Site: Caudal part of hindgut. D. Source: The epithelium of the a. Upper part of rectum is derived from the epithelium of the hindgut. b. Lower part of rectum is derived from dorsal part of endodermal cloaca. c. Smooth muscles and the connective tissues are derived from splanchnopleuric intra-embryonic mesoderm, surrounding the cloaca. E. Anomalies a. Imperforate anus: The commonest cause of imperforate anus is persistence of the anal membrane. b. Congenital rectovesical or rectourethral fistula. c. Congenital rectovaginal fistula. d. Ectopic anus.

364

Exam-Oriented Anatomy

¾ Proctoscopy: It is visualization of rectum and anal canal by proctoscopy. ¾ Sigmoidoscopy: It is visualization of sigmoid colon by sigmoidoscopy. ¾ Prolapse of rectum: It may be • Incomplete or mucosal prolapse of the rectum. • Complete prolapse or procidentia: The whole thickness of the rectal wall protrudes through the anus. OLA-54 Blood supply of anal canal Table 28.3: Blood supply of anal canal Particulars

Upper part of anal canal

Lower part of anal canal

• Arterial

• Superior rectal artery, a continuation of the inferior mesenteric artery. (the artery of the hindgut)

• Inferior rectal artery: It is main artery. It is a branch of the internal pudendal artery

• Venous

• Upper part > inferior mesenteric vein>splenic vein>portal vein.

• Lower part > inferior rectal • Vein > internal iliac vein common iliac vein > inferior vena cava

SN-73

White and pectinate lines of anal canal Table 28.4: White and pectinate lines of anal canal

Abdomen

3

Particulars

Pectinate line

White line of Hilton (transitional zone)

• Definition

• It is present at lower border of anal valve of Morgagni

• It is less vascular area of anal canal

• Width

• Thin

• Thick

• Mucosa

• Projected in mucosal folds and fixed to deeper structure

• Less mobile

• Situation

• Present at the junction of upper and middle zone • It is opposite to the middle of internal anal sphincter

• Level of the interval between the subcutaneous part of external anal sphincter and the lower border of internal anal sphincter.

• Embryological significance

• Junction of ectodermal and endodermal parts

• Ectoderm

• Nature

• Wavy

• Wide

LAQ-34 Describe anal canal under following heads 1. Gross anatomy, 2. Development, and 3. Applied anatomy.

Introduction: The terminal part of large intestine is called anal canal. It is devoid of A. Sacculations, B. Taenia coli, C. Appendices epiploicae

Rectum and Anal Canal

365

1. Gross anatomy A. Situation: It is situated in the anal between two ischiorectal fossae. a. Length: It is 4 cm long and situated about 4 cm in front and below the tip of the coccyx. b. Direction: Downwards, and backwards. B. External features a. Extent: It extends from anorectal flexure (½” below and 1" in front of tip of the coccyx) to the vertical slit between two buttocks. C. Relations a. Anterior relations are the structure at the base of urogenital I. Perineal body i. In male • Bulb of penis • Bulbospongiosus muscle ii. In female

: Lower part of vagina.

D. Posterior: Anococcygeal ligament. E. Laterally a. In the upper part: Levator ani. F. Interior of the anal canal: It is divided by pectinate and Hilton’s white line into parts (Fig. 28.6) a. Upper part (above the pectinate line) b. Length is 15 mm. It is lined by mucous membrane which shows 6–10 vertical folds. These folds are called anal column of Morgagni. They are prominent in children. They are ill defined in adults. c. The lower end of the anal columns is united to each other by short transverse folds of mucous membrane. These folds are called anal valves. d. Above each valve, there is a depression which is called anal sinus. There are about 10 mucous secreting anal glands. They open into the anal sinuses. e. The anal valves together form a transverse line called pectinate line (Fig. 28.6). G. Middle part (between pectinate and Hilton’s lines): a. This region is called pecten or transitional zone. There is no abrupt change in oesophagus to stomach. b. The lower limit of the pecten has a whitish appearance, hence it is called white line of Hilton. c. It is about 15 mm in length. d. It is lined by mucous membrane, which is bluish in appearance. It contains dense venous plexus which lies between mucosa and muscle coat.

3 Abdomen

b. In the lower part: External anal sphincter.

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Exam-Oriented Anatomy

Fig. 28.6: Interior of anal canal

Abdomen

3

e. Mucous is less mobile as compared to the mucosa of the upper part. Anal fissures are present in this zone. H. Lower part (cutaneous) (below Hilton’s line): a. It is about 8 mm long. b. It is lined by true skin containing sweat glands, sebaceous glands and hair follicle. The lining epithelium is stratified squamous keratinized. Table 28.5: Blood supply, nerve supply and lymphatics of anal canal Particulars

Above the pectinate line

Below the pectinate line

• Blood supply • Arterial

Particulars

• Superior rectal artery, a continuation of the inferior mesenteric artery. (the artery of the hindgut)

• Inferior rectal artery, a branch of the internal pudendal artery is the main artery.

• Venous

• Upper part is drained into portal system via superior rectal vein

• Lower part is drained into systemic vein via inferior rectal vein.

• Nerve supply • Sympathetic • Superior hypogastric plexus (L1, L2) and autonomic nerve (S2, S3, S4)

• Lower area is supplied by pudendal nerve (somatic nerve) via inferior rectal nerves. This area possesses all modalities of cutaneous sensation Contd.

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Table 28.5: Blood supply, nerve supply and lymphatics of anal canal (Contd.) Particulars

Particulars

Above the pectinate line

Below the pectinate line

• Parasympathetic

• Pelvic splanchnic (S2, S3, S4). This area is insensitive to modalities of cutaneous sensation.

—

Lymphatics (Fig. 28.7)

• Lymphatics are drained into internal iliac nodes

• Lower area is drained into horizontal set of superficial inguinal lymph nodes.

Fig. 28.7: Lymphatic drainage of anal canal

2. Development A. Chronological age: It develops in the 7th week of intrauterine life. B. Germ layer: Endoderm and ectoderm. C. Site: Terminal part of the hindgut. D. Sources a. Upper two-thirds of the anal canal develops from terminal part of the hindgut. b. Lower one-third develops from the proctodaeum. E. Anomalies . It results a. Imperforate anus occurs: 1:5000 infants. It is more common in males from abnormal development of urorectal septum. b. Anal agenesis: The anal canal may end blindly. c. Anal stenosis. 3. Applied anatomy ¾ Anal fissure: The lower end of anal columns is connected by small folds called anal valves. In chronic constipated persons, the anal valves may be torn due to

Abdomen

3

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Exam-Oriented Anatomy

faecal mass catching on fold of mucous membrane. The elongated ulcer is called anal fissure, which is very painful. ¾ Perianal abscess is due to the trauma to anal mucosa caused by faecal matter.

Fig. 28.8: Locations of anal abscesses and fistulous openings Note: Direction of arrow indicates spread of infection

Abdomen

3

¾ Anal fistulae are due to the spread of inadequately treated anal abscess. If the abscess opens only on one surface, it is called sinus. ¾ Incontinence associated with rectal prolapse is due to trauma and spinal cord injury. ¾ Haemorrhoids are saccular dilatations of the internal rectal venous plexus. They occur above the pectinate line and are, therefore, painless. They bleed profusely during straining at stool. ¾ Causes • Vessels are poorly supported by connective tissue • They are valve less. • Venous return decreases during defaecation. • Predisposing conditions ƒ Portal hypertension resulting from cirrhosis ƒ Pregnancy ƒ Cancerous tumour. ƒ Chronic constipation • Precipitating factors ƒ Familial tendency associated with leg vein varicosities. ƒ Most dependent part of portal circulation ¾ The details of the piles are described in Table 28.6

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Rectum and Anal Canal

Table 28.6: Details of the piles Particulars

Internal

External

• Site

• Upper half of anal canal

• Lower half of anal canal

• Constitution

• • • •

• Inferior rectal vein • Mucous membrane • Skin

• Position

• 3, 7, 11’O clock. This is a primary site.

• Degree

• 1°—Within anal canal • 2°—Extruded on defaecation • 3°—Prolapse on defaecation and remains outside

• Nerve supply

• Autonomic

• Inferior rectal nerve

• Clinical

• Painless, sensitive to stretch.

• Painful to touch, pain and pressure

• Position may be anywhere —

3 Abdomen

Superior rectal artery Superior rectal vein Mucosa Submucosa

29 Walls of Pelvis

OLA-55 Attachments to iliac spines Table 29.1: Attachments of iliac spines Spines

Attachments Muscles

Ligament

• Anterior superior iliac spine

• Sartorius in lower part

• Lateral end of inguinal ligament in upper part

• Anterior inferior iliac spine

• Straight head of rectus femoris in upper part

• Iliofemoral ligament in lower part

• Posterior superior iliac spine

• Erector spinae

• Posterior sacroiliac ligament and sacrotuberous ligament

• Posterior inferior iliac spine

• Piriformis

• Sacrotuberous ligament

SN-74

Internal iliac artery

Introduction: This is artery supplying the external genitalia, structures in the lateral pelvic wall, pelvic organs and gluteal region. 1. Origin: Internal iliac artery is one of the two terminal branches of common iliac artery given at sacroiliac joint. It supplies the pelvic walls, pelvic viscera, gluteal region, perineum and adductor compartment of the thigh. 2. Distribution: It supplies A. Pelvic organs, B. Perineum, C. Gluteal region, and D. Iliac fossa. 3. Features A. It lies within the parietal pelvic fascia. However, its branches pierce pelvic fascia to distribute the structures, except the obturator artery. B. It is approximately 4 cm long. 370

Walls of Pelvis

371

C. Internal iliac artery in the foetus, however, is double the size of the external iliac artery because it transmits blood to the placenta through the umbilical artery. D. The umbilical artery with internal iliac artery then forms a direct continuation of the common iliac artery. 4. Course A. It begins in front of the sacroiliac joint at the level of intervertebral disc between L5 and sacrum. It lies medial to psoas major muscle. B. It runs downwards and backwards and ends near the upper margin of greater sciatic notch. It divides into anterior and posterior divisions. 5. Relations: The artery is related A. Anteriorly

b. In females

and female

to ureter.

to the

I. Ovary, and II. Lateral end of uterine tube. B. Posteriorly a. Internal iliac vein, b. Lumbosacral trunk, and c. Sacroiliac joint. C. Laterally a. External iliac vein, and b. Obturator nerve. D. Medially a. Peritoneum, and b. Tributaries of internal iliac vein. 6. Branches: They are divided into (Fig. 29.1) A. Anterior division a. In male I. Collateral branches i. Obliterated umbilical artery, ii. Obturator artery, iii. Superior vesical artery, iv. Inferior vesical artery v. Middle rectal artery, II. Terminal branches i. Inferior gluteal artery, and ii. Internal pudendal artery. b. In female : It is important to note that in females , the inferior vesical artery is absent. It is replaced by two arteries, namely, the uterine and the vaginal.

3 Abdomen

a. In male

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Exam-Oriented Anatomy

Fig. 29.1: Branches of the right internal iliac artery

B. Posterior division breaks into three branches. They are all parietal branches. The the keyword is.

Abdomen

3

“SIL” Superior gluteal, Iliolumbar, and Lateral sacral arteries.

Mnemonics—Tip

Box 29.1 Note: The branches of anterior division of internal iliac artery can be remembered by the keyword O, O, SIM, GENERAL PRACTITIONER • The letter “O” represents obliterated umbilical artery. • The next letter “O” represents obturator. • The letter “S” represents superior vesical. • The letter “I” represents inferior vesical. • The letter “M” represents middle rectal. • The letter “G” represents inferior gluteal. • The letter “P” represents internal pudendal Things to note—Tip Box 29.2 Note: Obliterated umbilical artery is a continuation of the superior vesical, which is usually the 1st highest branch to arise from anterior division. It is to be noted that the internal pudendal and inferior gluteal vessels are considered terminal branches of the anterior division.

Walls of Pelvis

373

7. Applied anatomy ¾ Inferior mesenteric arteriogram is done by passing a catheter through internal iliac artery. ¾ Occasionally, the internal iliac artery is ligated to control pelvic haemorrhage. ¾ In kidney, transplantation renal vessels are anastomosed end-to-end to the internal iliac vessels. ¾ Blockage of internal iliac artery leads to impotence in males . Inferior vesical artery

Introduction: Inferior vesical artery is also called vesicular artery, although this adjective is derived from vesicula or vesicle, meaning ‘a small bladder’. It is present . Please remember that there is no inferior vesical artery in female . only in the male Instead it is represented by the uterine and the vaginal arteries (Fig. 29.2). 1. Origin: It is a branch of anterior division of internal iliac artery. 2. Course and relations: The inferior vesical artery runs forwards and medially, in the lateral true ligaments of the bladder, with the vesical veins. 3. Distribution: It supplies A. Trigone B. Lower part of urinary bladder, C. Lower end of the ureter, D. Urethra, E. Ductus deferens, F. Seminal vesicle, and G. Prostate. Main artery of prostate —Tip Box 29.3 Please note, inferior vesical artery is a main artery of the prostate. 4. Branches of inferior vesical artery: It gives two groups of branches, A. Urethral, and B. Capsular. C. The urethral vessels enter at the prostatovesical junction principally posteriorly at the 5 and 7 o’clock positions, but also, anteriorly at 1 and 11 o’clock. D. The capsular arteries run posterolaterally and inferiorly in the neurovascular bundle. It provides perpendicular perforating vessels to the prostate (Fig. 29.2). 5. The vaginal artery A. They are often 2 or 3 in number. . It passes B. It corresponds with the inferior vesical artery of the males downwards and medially to the vagina.

3 Abdomen

SN-75

374

Exam-Oriented Anatomy

Fig. 29.2: Origin, course, relation and branches of right inferior vesical artery

Abdomen

3

C. The vaginal artery anastomoses infront as well as behind the vaginal walls. a. It forms two longitudinal vessels • Anterior, and • Posterior azygos arteries of the vagina. b. It also gives branches to the lower part of the bladder wall and the anterior rectal wall. SN-76

Inferior gluteal artery

Introduction: It is the axial artery of the lower limb. 1. Origin: It is the largest branch of anterior division of internal iliac artery. 2. Course and relations A. It passes posteriorly between the 1st and the 2nd sacral ventral rami and pyriformis. B. It enters the gluteal region through the greater sciatic foramen. C. It then descends deep into the gluteus maximus muscle, over the obturator internus and gemelli, the quadratus femoris and extends into the upper part of the thigh (Fig. 29.3). 3. Branches: In pelvis, it supplies A. Muscular branches to all the muscles of pelvic walls. B. Visceral branches to the base of the bladder.

Walls of Pelvis

375

Fig. 29.3: Anastomosis between superior and inferior gluteal arteries at great trochanter of femur

, it supplies the seminal vesicles and the prostate.

D. Its other branches are as follows a. It gives a fine branch to the sciatic nerve called ‘arteria nervi ischidia.’ b. It provides an anastomotic branch to the cruciate anastomosis. c. A coccygeal branch runs towards the coccyx. d. Some branches are also given to the hip joint and to the skin of the gluteal region. 4. Applied anatomy ¾ Pus from pelvic cavity may enter the gluteal region along with inferior gluteal artery. ¾ Inferior gluteal artery is likely to bleed profusely during amputation of the thigh. ¾ One of the collateral pathways to the internal iliac artery is through inferior gluteal and deep artery of the thigh. SN-77

Iliolumbar artery

1. Origin: The iliolumbar artery is the 1st branch of the posterior trunk. 2. Course and relations: It lies anterior to the sacroiliac joint and lumbosacral nerve trunk. It lies posterior to the obturator nerve and external iliac vessels and reaches the medial border of psoas major. It then ascends superolaterally in a recurrent fashion turning sharply backward to the iliac fossa (Fig. 29.4). 3. Branches: It divides behind psoas major into A. Lumbar, and B. Iliac branches.

3 Abdomen

C. In males

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Exam-Oriented Anatomy

C. The lumbar branch supplies psoas major and quadratus lumborum and anastomoses with the 4th lumbar artery. It sends a small spinal branch through the intervertebral foramen. It passes between the 5th lumbar and 1st sacral vertebrae, to supply the cauda equina. D. The iliac branch supplies iliacus. It anastomoses with the iliac branches of the obturator artery. The site of anastomosis is between iliacus muscle and ilium bone. a. A large nutrient branch enters an oblique canal in the ilium. Other branches run around the iliac crest to supply the gluteal and abdominal muscles. They anastomose with the b. Superior gluteal, c. Circumflex iliac, and d. Lateral circumflex femoral arteries.

Abdomen

3

Fig. 29.4: Course and branches of iliolumbar artery

4. Applied anatomy ¾ In case of fracture dislocation of the sacroiliac joints, iliolumbar artery, which forms an anterior relation of the joint, torn and bleeds. ¾ The bleeding from the iliolumbar artery is in the retroperitoneal space, it can be alarming and may cause the death.