Exam-Oriented Anatomy, Volume 4: Questions and Answers [2 ed.] 9390046114, 9789390046119

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Volume

4

Exam-Oriented

naom Questions and Answers Second Edition □

□

Brain

Shoukat N Kazi

Thorax

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

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: 978-93-546-6177-8 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 Hajj an 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

I

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

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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)

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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 (1 ½ + 1½ + 1½years) 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 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

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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 r ed 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

Exam-Oriented Anatomy

viii

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 brachia! plexus. 13. Use of celebrities A. Mary Korn-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-PROV 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

I

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

I

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 VarunJain, 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

I

Contributors Arudyuti Chowdhury Ms. oGo 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 (0rtho)

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 obi iged 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 Salama! 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, OMA (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

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Brain: Animation A. Internal capsule

Sr. No.

Type of question

Topic

Time duration (minutes)

A/1

LAQ-26

Introduction and objectives of internal capsule

5.23

A/2

LAQ-26

Parts of internal capsule

1.56

A/3

OLA-31

Relations of internal capsule

2.06

A/4

LAQ-26

Composition of fibres of internal capsule

7.56

A/5

LAQ-26 and SN-74

Arteries of brain and internal capsule

3.08

A/6

LAQ-26 and SN-75

Venous drainage of internal capsule

1.42

A/7

OLA-25

Applied anatomy of internal capsule

4.18

A/8

OLA-26

Cartoon of internal capsule

6.24

B. Ascending tracts Sr. No.

Type of question

Topic

Time duration (minutes)

B/1

SN-78

Touch receptor

5.49

B/2

OLA-31 and OLA-32

Introduction to ascending and descending fibres

2.28

B/3

SN-10

Nomenclature of tract

3.20

B/4

SN-11

Grouping of tracts

2.56

B/5

SN-18

Synonymous of posterior column

1.45

B/6

OLA-8

Sensations carried by posterior column

1.47

B/7

SN-19

Pathway of posterior column

3.14

B/8

SN-1 7 and SAQ-3

Course of medial lemniscus

4.08

B/9

SN-22

Anterior spinothalamic tract

2.18

B/10

SN-23 and LAQ-5

Lateral spinothalamic tract

4.01

B/11

SN-24

Spinocerebellar tract

2.46

B/12

SN-25

Course of anterior or ventral spinocerebellar tract

2.03

B/13

SN-26

Course of posterior or dorsal spinocerebellar tract

1.42

B/14

SN-27

Course of cuneocerebellar tract

1.40

C. Descending tracts

I. Corticonuclear tract Sr. No.

Type of question

Topic

Time duration (minutes)

C/I/1

LAQ-4

Introduction of corticonuclear tract

2.11

C/I/2

LAQ-4

Origin of corticonuclear tract

1.37

C/I/3

LAQ-4

Modes of innervation of motor nuclei of cranial nerves

3.27

C/I/4

LAQ-4

Somatotopic representation of corticonuclear tract

0.59

C/1/5

LAQ-4

Course of corticonuclear tract at superior colliculus

1.35

C/I/6

LAQ-4

Course of corticonuclear tract.inferior colliculus

1.29

C/I/7

LAQ-4

Course of corticonuclear tract at pons

0.57

C/I/8

LAQ-4

Course of cortico nuclear tract at pontomedullary junction

2.41

II. Corticospinal tract Sr. No.

Type of question

Topic

Time duration (minutes)

C/11/1

LAQ-2

Introduction of corticospinal tract

2.56

C/11/2

LAQ-2

Course of corticospinal tract

4.59

D. Circle of Willis

Sr. No.

Type of question

Topic

Time duration (minutes)

D/1

SN-76

Circle of Willis

10.36

These high-value animation videos are available on CBSiCentral App through scratch code. Please see the front inner cover for obtaining access code.

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contents

iv

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

I

V

vi vii

1 Brain L__ _ _ _Section __ _ _ _ __

1. Introduction SN-1 OLA-1 SN-2 SN-3 SN-4 OLA-2

2. Meninges of the Brain and Cerebrospinal Fluid SN-5 SN-6 SN-7 SN-8 SN-9

SAQ-2 SN-10 SN-11 SN-12 SN-13 SN-14 SN-15

SN-16 SN-17

LAQ-1 LAQ-2 LAQ-3 LAQ-4 OLA-8 SN-18 SN-19 SAQ-3 SN-20

9

Cerebrospinal fluid 9 Choroid plexus 10 lnterpeduncular fossa 12 Arachnoid granulations (pacchionian bodies) 13 Cisterna magna (cisterna medullaris) 14

3. Spinal Cord OLA-3 OLA-4 OLA-5 OLA-6 OLA-7 SAQ-1

3

Neuroglia 3 Enumerate different types of neuroglial cells. What are their functions? 4 Oligodendrocytes 4 Astrocytes 5 Myelin sheath 6 Arterial supply of dura mater 7

15

Give extent of spinal cord 15 What is cauda equina? 16 What is a tract? 16 What is a lemniscus? 16 What is a peduncle? 17 What is ascending tract? Name the ascending tracts 18 What is descending tract? Name the descending tracts 18 What is the basis of nomenclature of tracts? 19 How the ascending tracts are grouped? 21 How the descending tracts are grouped? 21 Draw and label a transverse section of spinal cord showing external features 23 Draw and label a transverse section of spinal cord showing grey matter 23 Draw and label a transverse section of spinal cord showing main ascending and descending tracts 23 Lateral lemniscus 24 Medial lemniscus 25

SN-21 SN-22 SN-23 LAQ-5 SN-24 SN-25 SN-26 SN-27 LAQ-6

LAQ-7 SN-28 SN-29 SN-30

Extrapyramidal tracts 26 Corticospinal tract or pyramidal tract 28 Corticospinal tract 32 Corticonuclear tract 33 Enumerate the sensations carried by posterior column 38 Nomenclature of posterior column 38 Pathway of posterior column 39 Medial lemniscus 39 Somatotopic arrangement of fibres of posterior column in thalamus and brain 40 Modality arrangement of fibres of posterior column in the spinal cord 40 Anterior spinothalamic tract 41 Lateral spinothalamic tract 43 Lateral spinothalamic tract/describe the pathway of pain and temperature 43 Spinocerebellar tract 46 Course of anterior spinocerebellar tract 48 Course of posterior spinocerebellar tract 49 Course of cuneocerebellar tract 50 Posterior column/tract of Goll and Burdach/fasciculus gracilis and cuneatus/tract of conscious proprioceptive impulses 51 Pathway of unconscious proprioceptive impulses 56 Development of spinal cord 57 Neural crest 59 Neural tube 60

4. Cranial Nerves OLA-9 SN-31 LAQ-8

SN-32 SN-33 SN-34

62

Enumerate the nuclei associated with 5th cranial nerve 62 Medial longitudinal bundle (fasciculus) 62 Visual (optic) pathway and the effects of lesion of different parts of visual pathways 63 Pathway of light reflex 66 Pathway of accommodation reflex 66 Pathway of hearing (auditory pathway) 68

Exam-Oriented Anatomy

xvi

5. Brainstem LAQ-9 LAQ-10 SN-35 LAQ-11

SN-36 LAQ-12

LAQ-13

SN-37 SAQ-4 OLA-10 SAQ-5 LAQ-14 SN-38 SN-39 SN-40 SAQ-6 LAQ-15 SN-41 LAQ-16 SN-42

SN-43

SAQ-7 SN-44 LAQ-17

SN-45 SN-46 SN-47

Draw and label ventral surface of the brainstem 69 Pyramidal decussation 69 Blood supply of medulla oblongata 71 Draw and label a transverse section of medulla oblongata at the level of pyramidal decussation 72 Arcuate fibres 73 Draw and label a transverse section of medulla oblongata at the level of sensory decussation 75 Draw and label a transverse section of medulla oblongata at the level of inferior olivary nucleus or pontomedullary junction 76 Name the cranial nerve nuclei in medulla oblongata 77 Name the cranial nerve nuclei in midbrain? 78 Name the cranial nerve and nuclei at pontomedullary junction 79 Name the cranial nerve nuclei in pons 80 Draw and label a transverse section of pons at the level of facial colliculus 81 Draw and label TS of pons at lower level showing exit of cranial nerves 82 Draw and label TS of pons at lower level showing blood supply 82 Draw and label TS of pons at lower level showing features 83 Stria medullaris 83 Draw and label TS of pons at upper level 84 Draw and label TS of pons at upper level showing blood supply 85 Draw and label a TS of midbrain at the level of inferior colliculus 86 Draw and label a TS of midbrain at the level of inferior colliculus showing features 87 Draw and label a TS of midbrain at the level of inferior colliculus showing blood supply 87 Trapezoid body 87 Crus cerebri 88 Draw and label a transverse section of midbrain at the level of superior colliculus 90 Lateral medullary syndrome (Wallenberg's syndrome) 90 Medial medullary syndrome 91 Dentate nucleus 92

6. Cerebellum SN-48 SN-49 OLA-11 SN-50 SN-51 SN-52 SN-53 LAQ-18 SN-54 SN-55

69

94

Classify the cerebellum as per evolution and function 94 Parts of vermis of cerebellum 95 Name the nuclei of cerebellum 95 Archicerebellum 96 Paleocerebellum 98 Neocerebellum 99 Cerebellar peduncles 101 Inferior cerebellar peduncle 102 Histology of cerebellum 104 Purkinje cells 106

7. Fourth Ventricle LAQ-19

Floor of fourth ventricle

8. Cerebrum SN-56 SN-57 SN-58 SN-59 OLA-12 OLA-13 SN-60 LAQ-20

LAQ-21 OLA-14 OLA-15 OLA-16 OLA-17 SN-61 SN-62 SN-63 SN-64 SN-65 SN-66 SN-67 SN-68 OLA-18 OLA-19 SN-69 LAQ-22 LAQ-23 SN-70 OLA-20 SN-71 SN-72 SN-73 LAQ-24 OLA-21 LAQ-25 LAQ-26 OLA-22 OLA-23 OLA-24 OLA-25 OLA-26 OLA-27 OLA-28

OLA-29

108 108

112

Substantia nigra 112 Tectum of midbrain/colliculi/corpora quadrigemina 113 Pretectal nucleus 114 Red nucleus 115 Name any four nuclei of thalamus 118 Name any four nuclei of hypothalamus 118 Trigeminothalamic tract 119 Draw and label sulci, gyri and functional areas of superolateral surface of cerebral hemisphere 120 Blood supply of cerebral hemisphere 121 Mention the function of paracentral lobule 125 Mention the function of auditory area 125 Mention the function of area no. 43 125 Mention the function of area no. 28 125 Primary motor area 125 Premolar area 127 Sensory speech area of Wernicke 128 Motor speech area of Broca 128 Thalamus 129 Medial geniculate body 131 Lateral geniculate body 132 Pineal body 134 What are the cells of posterior pituitary? 135 What are Herring bodies? 135 Hypothalamohypophyseal tract 135 Hypothalamus 136 Basal nuclei 138 Corpus striatum 142 Name the parts of the caudate nucleus 143 Caudate nucleus 143 Amygdaloid body 144 Trigeminal nucleus 145 Define and classify white matter of cerebrum 146 Name the parts of the corpus callosum 148 Corpus callosum 148 Internal capsule 152 What is internal capsule? 155 What are parts of internal capsule? 155 What are the functions of fibres present in internal capsule? 155 What is applied anatomy of internal capsule? 156 What are projection fibres? 157 What is corona radiata? 158 What are ascending fibres passing through the internal capsule and their functions? 158 What are descending fibres passing through the internal capsule and their functions and effect of lesion? 159

Contents OLA-30

OLA-31 SN-74 SN-75 SN-76 SN-77 SN-78 OLA-32 SN-79 SN-80 SN-81

What is capsule? What is the basis of nomenclature of various terms used in relations of internal capsule? 159 What are relations of internal capsule? 160 What is the arterial supply of internal capsule? 161 Venous drainage of internal capsule 162 Circle of Willis 163 Betz cells 166 Touch receptor 167 Central sulcus 168 Granular cortex 169 Agranular cortex 169 Cerebrum 170

9. Third Ventricle, Lateral Ventricle and Limbic System 174 LAQ-27 SN-82 LAQ-28 OLA-33

Limbic system 174 Fornix 177 Third ventricle 178 Enumerate the structures situated in the floor of the body of lateral ventricle 180

xvii OLA-34 SN-83 OLA-35 SN-84 SN-85 SN-86 SN-87 SN-88

Name the parts of the lateral ventricle 180 Parts of lateral ventricle 180 Enumerate the structures forming the floor of inferior horn of lateral ventricle 181 Inferior horn of lateral ventricle 182 Posterior horn of lateral ventricle 183 Central part of lateral ventricle 184 Anterior horn of lateral ventricle 185 Hippocampus (seahorse) 185

10. Some Neural Pathways and Reticular Formation LAQ-29

Reticular formation

188

188

11 . Blood Supply of Spinal Cord and Brain 191 SN-89 SN-90 SN-91 SN-92 SAQ-8

Branches of vertebral artery 191 Blood- brain barrier 192 Blood supply of spinal cord 193 Branches of basilar artery 196 Branches of basilar artery 197

l ___________

s_e_cti_·o_n_2_T_h_o_ra_x_ _ _ _ _ _ _ _ _ __ 201

SN-11

What is 'sternal angle' and state its clinical importance? 201 Name the curvatures of vertebral column and classify them 201 Angle of Louis/sternal angle 202 Costa! cartilage 203 Structures related to superior surface of 1st rib 204 lntervertebral disc 205 Typical spinal nerve 206

SN-12 SN-13 SN-14 SN-15

12. Bones and Joints of Thorax OLA-1 OLA-2 SN-1 SN-2 SN-3 SN-4 SN-5

13. Wall of Thorax LAQ-1 SN-6 SN-7

I ntercostal space 208 Azygos vein 212 Typical intercostal nerve

208 214

14. Thoracic Cavity and Pleurae OLA-3 OLA-4 OLA-5 SN-8 SN-9 LAQ-2

15. Lungs OLA-6 OLA-7 OLA-8 SN-10

LAQ-3

Draw and label structure of the roots of the right and left lungs 225 Azygos lobe 226 Blood supply of lung 227 Movements of respiration 228 Suprapleural membrane (Sibson's fascia) 229 Draw and describe bronchopulmonary segment 230

16. Mediastinum SN-16 LAQ-4 SN-17 SN-18 SN-19

Mediastinum (partition) 235 Superior mediastinum 236 Anterior mediastinum 238 Middle mediastinum 240 Posterior mediastinum (longest)

17. Pericardium and Heart 215

What is pulmonary ligament? What is its function? 215 Enumerate recesses of pleura 215 Give applied anatomy of pleura and pleural cavity 216 Nerve supply of pleura 217 Costodiaphragmatic recess 218 Parietal pleura 219

222 Visceral relations of right lung 222 Visceral relations of left lung 222 Difference between right and left lungs 223 Mediastinal surfaces of the right and left lungs 223

OLA-9 LAQ-5 LAQ-6 SN-20 SN-21 SN-22 OLA-10 LAQ-7 OLA-11 SN-23 SN-24 SN-25

235

240

243

Pericardia! effusion 243 Fibrous pericardium 243 Serous pericardium 245 Name the derivatives of sinus venosus 248 Transverse sinus (intervisceral space) 248 Oblique sinus 250 State the structures opening into right atrium 250 Right atrium 251 Name the aortic sinuses giving origin to coronary arteries 254 Peculiarities of coronary arteries 254 Applied anatomy of coronary arteries 255 Arteries involved in myocardial infarction 257

xviii

I LAQ-8 SN-26 OLA-12 LAQ-9 OLA-13 OLA-14

LAQ-10 SN-27 SN-28 SN-29 SN-30 OLA-15 SN-31

Exam-Oriented Anatomy Right coronary artery 258 Blood supply of cardiac conduction system 260 Name any two branches of left coronary artery 261 Left coronary artery 261 Name the parts of heart tube 263 Name the structures that fuse with each other at the level of atrioventricular canals so as to separate right and left side of the heart 264 Venous drainage of the heart 264 Development of interatrial septum 265 Development of interventricular septum 267 Development of left atrium 269 Development of portal vein 269 Tributaries of inferior vena cava 270 Development of inferior vena cava 271

OLA-18 OLA-19 LAQ-12 SN-32 OLA-20 SN-33

19. Trachea, Oesophagus and Thoracic Duct LAQ-13 OLA-21 OLA-22 OLA-23

18. Superior Vena Cava, Aorta and Pulmonary Trunk 272 OLA-16 LAQ-11 OLA-1 7

Draw and label microscopic structure of small bronchus 272 Superior vena cava 272 Name developmental components of arch of aorta 275

Name developmental components of right subclavian artery 275 Name the arteries derived from 1st, 2nd, 3rd, 4th and 6th aortic arch arteries 276 Arch of aorta 2 76 Ligamentum arteriosum 281 What is ductus arteriosus? What is its function? When does it close? 282 Patent ductus arteriosus 282

OLA-24 LAQ-14 LAQ-15 Index

283

Trachea 283 Enumerate the constrictions in oesophagus 287 What is the lining epithelium of oesophagus? 287 What is the peculiarity of the musculature of oesophagus? 287 Where do we find glands in oesophagus? What is their clinical importance? 288 Oesophagus 288 Thoracic duct 293 297

SECTION

1 Brain Introduction Meninges of the Brain and Cerebrospinal Fluid Spinal Cord Cranial Nerves Brainstem Cerebellum Fourth Ventricle Cerebrum Third Ventricle, Lateral Ventricle and Limbic System Some Neural Pathways and Reticular Formation Blood Supply of Spinal Cord and Brain

Attention Please All the text in boxes are not to be written in the examination. It may • Signify the meaning of the word. • Represent cartoon All the cartoons are drawn to make the subject to be memorized. They may not have any role in the subject. They are not supposed to be drawn while writing the answer of the question.

CHAPTE R

1 Introduction

SN-1

Neuroglia

Definition: These are non-excitable, supporting cells of nervous system. They are described in Table 1.1. Table 1.1: Types of neuroglia, their situation, functions and development

Type • Macroglia - Oligodendrocyte (few processes) • Intrafascicular • Perineuronal -Astrocyte (star * shaped) - Protoplasmic, thick and symmetrical processes - Fibrous, thin and asymmetrical processes

Site

• Myelinated tract • Surface of the body of neurons • Grey matter • White matter

Function

}

Development

• They give support and form myelin sheath

• Ectoderm

• Microglia, small, flattened cell body with short processes

• More in grey than white matter, near capillaries

• Phagocytosis

• Mesoderm

• Ependymal cell

• Ventricle of the brain and spinal cord

• Secretes CSF

• Ectoderm

• Satellite or capsular companion

• Sensory or autonomic ganglion

• Supports and protects the neuron

• Ectoderm

• Schwarm cell

• Peripheral nerve

• Myelin sheath

• Ectoderm

3

4

I

Exam-Oriented Anatomy Posterior

~

Oligodendrocyte--~

+

Anterior Satellite cell~)~\:• • Ganglion Neuronal process Schwann cell

+

C:

C1l ,_

c::o

~--Ependymal c e l l o

Microglial cell--- ~

Fig. 1.1 : TS of spinal cord showing spinal nerve and all neuroglia

l•)f+I ■ Enumerate different types of neuroglial cells. What are their functions? Please refer Fig. 1.1. Protoplasmic and fibrous astrocyte (SN-1) Neuroglial cells neuron (Gk)-nerve; gloia (Gk)-glue 1. Astrocytes A. Structure: They are star * shaped cells. These are of two types, a. Protoplasmic, and b. Fibrous. B. Functions a. They are concerned with nutrition of the nervous tissue. b. They form blood-brain barrier. C. Absent in

a. Pineal gland, and • b. Posterior pituitary. 2. Oligodendrocytes (Gr. oligos-little, few; dendron-tree) are counterparts of the Schwarm cells. Schwarm cells myelinate the peripheral nerves. Oligodendrocytes myelinate the tracts. 3. Microglia (Gr. microglia-small glue) behave like macrophages of the central nervous system. They develop from mesoderm. 4. Ependymal cells are columnar cells lining the cavities of the central nervous system. Since the glial cells are capable of dividing, they can form the central nervous system tumour. SN-2

Oligodendrocytes

(Oligo-few) 1. Definition: These are neuroglial cells present in the central nervous system (Fig. 1.2).

Introduction

5

2. Features A. They are smaller than astrocytes. B. They have small, few, thin, short processes without excessive branching. C. They have cytoplasmic branches that extend radially. D. They do not surround multiple and unmyelinated axons. 3. Functions A. In the white matter, the oligodendrocytes form myelin sheaths around numerous axons. B. They myelinate the axon for insulation. C

ro ,_

co

Oligodendrocyte

Fig. 1.2: Oligodendrocyte

4. Staining: They are stained with silver impregnation-Cajal method. 5. Situation: They are found in both the grey and white matters of the central nervous system. A. They are analogous to Schwarm cells in peripheral nervous system. B. Ultrastructure of an oligodendrocyte in the central nervous system: The cytoplasm of the cell exhibits a well-developed

a. Granular endoplasmic reticulum, b . Golgi apparatus, c. Free ribosomes which are numerous, d. Myelinated axons. It shows oval, dark-staining I. Mitochondria, and II. Numerous neurofilaments. SN-3

Astrocytes

(Gr. Astron-star) Please refer Fig. 1.1. Protoplasmic and fibrous astrocyte (SN-1) 1. Features

*

A. These are small shaped cells. B. They give off a number of processes. C. The processes are often flattened into leaf-like laminae. D. Laminae surround neurons and separate them from other neurons. E. The processes end in expansions in relation to blood vessels or in relation to the surface of the brain. F. There are small swellings present on the processes called gliosomes.

s

I

Exam-Oriented Anatomy

G. These swellings are rich in mitochondria. H . The processes of one astrocyte are united with other astrocytes through gap junctions. I. They communicate with one another through calcium channels. J. Such communication plays a role in regulation of synaptic activity and in the metabolism of neurotransmitters and neuromodulators. 2. Types: There are two types of astrocytes: Fibrous and protoplasmic. A. Fibrous astrocytes a. Present in white matter. C: b . Their processes are thin and are asymmetrical. C1l ,_ c::o B. Protoplasmic astrocytes a. Present in grey matter. b. Their processes are thicker and symmetrical. c. Protoplasmic extensions of astrocytes surround nodes of Ranvier. 3. Functions A. They provide mechanical support to neurons. B. They serve as insulators and prevent neuronal impulses from spreading in unwanted directions. C. They help in the formation of blood-brain barrier. D. Astroglial cells are also responsible for repair of damaged areas of nervous tissue. They proliferate in such regions (gliosis). SN-4

Myelin sheath

1. Features

A. It is present outside the axolemma. B. Schwarm cells form myelin sheath in peripheral nervous system. C. Oligodendrocyte cells form myelin sheath in central nervous system. 2. Formation of myelin sheath A. An axon invaginates into the cytoplasm of the Schwann cell. The axon is suspended by a fold of the cell membrane of the Schwarm cell. The fold is called the mesaxon. B. The mesaxon becomes greatly elongated. It spirally winds around the axon. It is thus surrounded by several layers of cell membrane. C. Lipids are deposited between adjacent layers of the membrane. D. These layers of the mesaxon, along with the lipids, form the myelin sheath. 3. Formation of neurilemmal sheath: Outside the myelin sheath, there is a thin layer of Schwarm cell. It forms an additional sheath that is called the neurilemma (also called the neurilemmal sheath or Schwarm cell sheath). A. At the junction of any two segments, there is a short gap in the myelin sheath. These gaps are called the nodes of Ranvier.

Introduction

7

B. The nodes of Ranvier have great physiological importance. When an impulse travel down a nerve fibre it does not proceed uniformly along the length of the axis cylinder. But it jumps from one node to the next. This is called saltatory

conduction. C. The segment of myelin sheath between two nodes of Ranvier is called intemode. Node of Ranvier

Schwann cell

C

ro ,_

Axon

Myelin sheath

A

Sc~~~l:~~~r

..·ci·-........ 0 - · · · Schwann c eol lo $ S II ·. ma axon : Neurolemmal sheath--! Q : Myelin sheath Nucleus of O O _:' enclosing Schwann cell \ ...... ../ axis cylinder

B

C Fig. 1.3: Myelin sheath

4. Composition of myelin sheath A. Lipids: It includes a. Cholesterol, and b. Phospholipids. Apart from these lipids, there are other lipids which are in smaller quantities. B. Proteins, and C. Water. 5. Functions of the myelin sheath A. The myelin sheath helps to increase the velocity of conduction (for a nerve fibre of the same diameter). B. It reduces the energy spent in the process of conduction. C. The colour of the white matter is due to myelin sheath. 6. Applied anatomy ►

In multiple sclerosis, myelin formed by oligodendrocytes undergoes degeneration. The myelin formed by Schwann cells is spared.

(•)tfWArterial supply of dura mater The outer layer is richly vascular. The inner meningeal layer is more fibrous and requires little blood supply.

co

a

I

Exam-Oriented Anatomy Table 1.2: Arterial supply of dura mater

Dura mater of

Arteries

• Vault of skull

• Middle meningeal artery, branch of maxillary artery

• Anterior cranial fossa

• Meningeal branches of - Anterior ethmoidal, - Posterior ethmoidal, and - Ophthalmic arteries

• Middle cranial fossa

• • • •

• Posterior cranial fossa

• Meningeal branches of the - Vertebral, - Occipital, and - Ascending pharyngeal arteries

C:

C1l ,_

c::o

Middle meningeal, Accessory meningeal, Internal carotid arteries, Meningeal branches of the ascending pharyngeal artery.

CHAPTER

2 Meninges of the Brain and Cerebrospinal Fluid SN-5

Cerebrospinal fluid

1. The CSF is modified tissue fluid (Fig. 2.1). It is present in A. Ventricles of brain,

B. Subarachnoid space around brain, and C. Spinal cord. 2. Formation A. The bulk of the CSF is formed by choroid plexus lining lateral ventricle.NEEr B. Small amount is formed by choroid plexus of 3rd and 4th ventricles. C. The total quantity: About 150 ml. D. Rate of formation: 200 ml/hour and 5000 ml/day. E. Normal pressure: 60 to 100 mm H 20. 3. Circulation Lateral ventricle _

F_or_am _e_ n _of_ M_ o_m_o_

3rd ventricle

_ ce_re_b_ r al_ a_ou _e_du_c_ t _

. l Median and lateral apertures 4th ventnc e - - - - - - - - - - - Subarachnoid space. 4. Absorption A. Chiefly absorbed through a. Arachnoid villi, and b. Arachnoid granulation. B. Partly by a. Perineural lymphatics around the 1st, 2nd, 7th and 8th cranial nerves, and b. Veins related to spinal nerves. 5. Functions A. Protection of brain, B. Nutrition of brain and coverings, and C. Removal of waste products from brain. 9

10

I

Exam-Oriented Anatomy

Superior Posterior+ Anterior Inferior

Choroid plexus of --+-+-lateral ventri cal - ~ C:

\ ~

IVth ventricle - ~,.---~

C1l ,_

c::o

Foramen of "Magendie"

'

Late,al ,eot,ide

~~----=-~-----;;fj'- II Ird ventricle

~ -- Cerebral aqueduct ~ - - - - Foramen of Luschka

fP, Subarachnoid space - --

Fig. 2.1: Cerebrospinal fluid

6. Applied anatomy ►

►

►

CSF can be obtained by • Lumbar puncture, • Cisternal puncture, and • Ventricular puncture. Biochemical analysis of CSF is of diagnostic value in various diseases. Obstruction to the flow of CSF in the ventricular system leads to hydrocephalus in children and raised intracranial pressure in adult.

SN-6

Choroid plexus

Introduction: It is tuft of capillaries covered by pia mater and ependymal cells. They are lined simple, ciliated columnar epithelium present in the ventricles of brain (Fig. 2.2). 1. Gross anatomy A. Site: Present at the site where pia mater and ependyma come close together. B. Examples a. CSF is mainly produced by choroid plexus of central part and inferior horn of lateral ventricle.NEET b. Roof of I. 3rd ventricle. IL 4th ventricle (Fig. 2.3). C. Structure: It consists of minute tuft of capillaries covered by pia mater and ependyma. D. Age changes: Calcification of choroid plexus occurs in late age. It is present at the junction of body and inferior horn of lateral ventricle.

Meninges of the Brain and Cerebrospinal Fluid

11

Pia mater

C

ro ,_

co Fig. 2.2: Choroid plexus Superior Posterior+ Anterior Inferior Choroid plexus of----.,L-~ lllllllllllllllllllllli,. lateral ventrical

Choroid plexus - - -of IVth ventricle

,,f;

IVth ventricle _ _ _ /

Lateral ventricle

Cerebral aqueduct

U

Fig. 2.3: Choroid plexus in ventricles

2. Blood supply

A. Arterial supply

a. Anterior choroidal artery, a branch of internal carotid artery. b. Posterior choroidal artery, a branch of posterior cerebral artery. c. Posterior inferior cerebellar artery (PICA), the largest branch of vertebral artery. B. Venous drainage by choroid vein, combines with thalamostriate vein-to form internal cerebral vein > great cerebral vein > straight sinus > transverse sinus> sigmoid sinus. 3. Functions: Formation of cerebrospinal fluid by ultrafiltration.

4. Applied anatomy ►

Hydrocephalus: It is caused by • Neural tube defect, • Meningitis, • Brain tumour, and • Choroid plexus tumour.

12 ►

I

Exam-Oriented Anatomy

Calcification of choroid plexus can be visualized by radiography, which is important in differentiating tumour of pineal gland . •

SN-7

lnterpeduncular fossa

Introduction: It is a lozenge ♦ shaped space present between the cerebral peduncles of the midbrain. 1. Gross anatomy c: A. Shape: Rhomboid • B. Boundaries a. Anteromedially: Optic chiasma ,C shaped b. Anterolaterally: Optic tract. c. Posteriorly: Upper border of pons. d. Posterolaterally: Crus cerebri. C. Forms: Floor of IIIrd ventricle. D. Contents: They are described from anterior to posterior. a. Tuber cinerium: Slightly raised area of grey matter between mammillary body and optic chiasma.

£

S+r Inferior

~~~~ J ~~(') /~ ,

/ } , ~ Optic chiasma

Tuber cinerium ---...,,__ )~ with infundibulum Mammillary body Posterior perforated substance

~;7 •9 9 •.

Optic tract Basis pedunculi of midbrain

Fig. 2.4: lnterpeduncular fossa

b. Infundibulum: It suspends hypophysis cerebri. c. Posterior perforated substance: It is grey matter perforated by I. Posterior cerebral arteries, and IL Inferior cerebellar arteries. 2. Relations A. Anterolateral: Anterior cerebral artery. B. Posterior: Posterior cerebral artery. C. Posterolateral: Posterior communicating artery.

Meninges of the Brain and Cerebrospinal Fluid

13

3. Applied anatomy ► ►

Aneurysm of circle of Willis compresses optic chiasma and results into hemianopia. The pressure on hypophysis cerebri produces bitemporal hemianopia due to interruption of crossed nasal fibres.

SN-8

Arachnoid granulations (pacchionian bodies)

Introduction: These are finger-like projections, which project into dural venous sinuses. These are due to collection of arachnoid villi, which are the sites for the absorption of c cerebrospinal fluid (Fig. 2.5). ~ 1. Situation: They are situated along the sides of superior sagittal sinus, present on co the medial border of parietal bone. 2. Structures: These are small, granular bodies. A. Each arachnoid villus is a diverticulum in the subarachnoid space. B. It is covered by a thin cell layer which in tum is covered by endothelium of venous sinus. C. Age changes: It erodes the inner table of skull as the age advances. 3. Functions A. It is a main site for absorption of cerebrospinal fluid. B. It allows cerebrospinal fluid to pass to the venous spaces. C. It prevents reflux of blood. 4. Applied anatomy ► ► ►

Clotting of blood in the superior sagittal sinus blocks these safety valves and causes rapid increase in cerebrospinal fluid. The granulations increase with the advance of age. The age of person can be roughly determined by presence of granulations. Congenital absence of the arachnoid granulations is observed in hydrocephalus.

s+, Inferior

Superior sagittal ---------=;;;,---=------, sinus 1----Dura mater Arachnoid-----~ granulations Arachnoid m a t e r - - - - - - -~ ::---.

Fig. 2.5: Arachnoid granulations

14

I

SN-9

Exam-Oriented Anatomy Cisterna magna (cisterna medullaris)

(Cisterna-cavity, closed sac) Introduction: It is an enlarged subarachnoid space between the anteroinferior surface of cerebellum and posterior surface of medulla oblongata. 1. Shape: It is ..... lar in sagittal section.

2. Relations A. Anteriorly: Posterior surface of medulla oblongata. B. Posteriorly: Anterior and inferior surface of cerebellum. C: ~ 3. Communications c::o A. It receives cerebrospinal fluid from a. Roof of 4th ventricle (through foramen of Magendie). b. Lateral recess of 4th ventricle (through foramina of Luschka). B. It communicates a. Inferiorly: With spinal subarachnoid space. b. Anteriorly: With pontine cistern. Superior Posterior+ Anterior Inferior

Cerebellum Arachnoid mater

(

Pons

' Cisterna magna ~

~Medulla oblongata

!/

Fig. 2.6: Cisterna magna

4. Applied anatomy ► ►

Cistemal puncture: Cerebrospinal fluid can be tapped through the posterior atlanto-occipital membrane. It is rarely performed. Tumour in the space obstructs the circulation of CSP and results into hydrocephalus.

CHAPTER

3 Spinal Cord

l•)f+fl Give extent of spinal cord. 1. Extent (Fig. 3.1)

A. Adult: It extends from upper border of atlas vertebra to the lower border of 1st

lumbar vertebra. B. In children, it extends up to 3rd lumbar vertebra. 2. Continuation A. Superiorly, it is continuous with the medulla oblongata.

B. Inferiorly, it terminates as conus medullaris. 3. Vertebral column: It occupies upper two-thirds of vertebral canal and is enclosed in 3 meninges.

Superior

+

Inferior

II

Medulla oblongata - - - ,-+-~--,....,..

\ C1

'-t---

Upper border of 1st cervical

Spinal cord

__]_ ..--+------+-, \

L1 Lower border of 1st lumbar

Filum - ---+1 terminal is

Fig. 3.1 : Extent of spinal cord 15

1s

I

Exam-Oriented Anatomy

(•)tll What is cauda equina? 1. The word "cauda" means tail and "equina" means horse (Fig. 3.2).

2. It constitutes Table 3.1: Number of structures present in the cauda equina

Nerve roots

C:

C1l ,_

c::o

• • • • •

Lumbar: 2, 3, 4, and 5 Sacral: 1, 2, 3, 4, and 5 Coccygeal Conus medullaris Filum terminale

4 5 1

4 5 1

Total

4 5 1 1 1

4 5 1

16 20

4 1 1 42

All these nerves look like a tail of the horse.

Fig. 3.2: Cauda equina

(•)tJW What is a tract? The smallest bundle of fibres connecting any two masses of grey matter is called tract. It has same origin, course and destination.

(•)ti·•

What is a lemniscus?

Lemniscus (pl. lemnisci) : The larger bundle of fibres connecting various masses of grey matter is called lemniscus. Many tracts combine together to form lemniscus (Fig. 3.3)

Spinal Cord

17

Superior Right + Left Inferior

,._-,...;~ (-,'-,'~ - - Ventro Postero Lateral ..._ nucleus of thalamus

C

ro ,_

co

Anterior spinothalamic tract

c-,•-D

Fig. 3.3: Formation of medial lemniscus

What is a peduncle?

Peduncle: The biggest bundle of fibres connecting various grey matters is called peduncle. Many lemnisci combine together to form peduncle.

S+• Inferior

Inferior Optic chiasma

M;d:~::

Optic tract

00

q)t ~

Cerebellum---~ t• Cerebral ) ) peduncle +-+--

Midbrain

Medulla oblongata

\

Pons A. Cerebral peduncle

P

-r;;

B. Cerebellar peduncle

Fig. 3.4: Peduncles

Sopec,cj ~ ~ 7 1 M,ddle (3~ J1 ~ lnfenor

1a I SAQ-1

Exam-Oriented Anatomy

M1)@UJ.ftd§,1• 1 •i·IIH§ilh·1n\Ji,ti·Md§,t• 1 •i·•IH4t -

1. Ascending tracts: Fibres arising from the nuclei of spinal cord and reaching the nuclei of brainstem, cerebellum, and/ or nuclei of cerebrum, are called ascending tracts (Fig. 3.5). 2. Ascending tracts are A. Spinothalamic, a. Anterior spinothalamic b. Lateral spinothalamic B. Spinocerebellar C: C1l ,_ a. Anterior spinocerebellar c::o b. Posterior spinocerebellar C. Spino-olivary. Superior Right + Left Inferior

..,.__,.H--l_.,,.__--+-_ Ventro Postero Lateral ...,._

nucleus of thalamus

H - - - - - - - - --

Spinothalamic tract

Fig. 3.5: Ascending tract SAQ-2

What is descending tract? Name the descending tracts.

1. Descending tracts: Fibres arising from the grey matter of cerebrum, nuclei of

cerebrum, cerebellum and brainstem and reaching nuclei of spinal cord are called descending tracts (Fig. 3.6).

Spinal Cord

19

2. Examples of descending tracts

A. Corticospinal, B. Rubrospinal, C. Vestibulospinal, D. Olivospinal, and E. Reticulospinal. Superior Right + Left Inferior

C

ro ,_

co

lotemal capsole ~

~~ i+---+-)-- Corticospinal fibres

Motor cranial ---------nerve fibres

Motor cortex -

t--f--- Decussation of pyramids Corticospinal tract

Motor spinal ~ nerve fibres

"-.,.

_ __:,__ _-w,j,-,J-1

Fig. 3.6: Descending tract

SN-1 O

What is the basis of nomenclature of tracts?

The nomenclature of the tracts depends upon 1. Origin and destiny of the tract: The 1st word of the tract indicates the origin and the last word indicates the destiny of the tract: They are divided into ascending and descending tracts.

20

I

Exam-Oriented Anatomy

A. Examples of descending tracts

a. Corticospinal: It arises from grey matter of cerebral cortex and ends in nuclei of spinal cord. b. Rubrospinal: It arises from red nucleus of midbrain and ends in nuclei of spinal cord. c. Vestibulospinal: It arises from vestibular nuclei of medulla oblongata and ends in nuclei of spinal cord. d . Olivospinal: It arises from inferior olivary nuclei of brainstem and ends in nuclei of spinal cord C: e. Reticulospinal: It arises from reticular nuclei of brainstem and ends in nuclei C1l ,_ of spinal cord. c::o B. Examples of ascending tracts a. Spinothalamic tract: It arises from nuclei of spinal cord and ends in nuclei of thalamus. b. Spinocerebellar tract: It arises from nuclei of spinal cord and ends in nuclei of cerebellum. 2. Course of the tract: The first word of the tracts signifies the course of the tract. For example, A. Lateral spinothalamic tract courses through the lateral column of the spinal cord. B. Anterior spinothalamic tract courses through the anterior column of the spinal cord. 3. Relation with other tracts of same destiny: The words prefixing the tract having the same destiny indicate the relation of the tract with each other. For example, A. Anterior spinocerebellar tract: It is anterior to posterior spinocerebellar tract. B. Posterior spinocerebellar tract: It is posterior to anterior spinocerebellar tract. 4. Depending upon the level of consciousness A. The fibres reaching the grey matter of spinal cord and action taking place at the level of spinal cord is called local reflex action. B. The fibres reaching cerebellum and response given without knowledge of brain is called unconscious proprioceptive tract. C. The fibres reaching cerebrum and the response given by analysing the situation with previous experience is called conscious proprioceptive tract. 5. Shape of target nucleus. A. The word 'gracilis' means long and slender. The fibres of fasciculus gracilis end in gracilis tubercle that is long and slender. Hence, it is called fasciculus gracilis.

B. The fibres of fasciculus cuneatus end into nucleus cuneatus. The word 'cuneatus' means wedge shaped. The fibres of fasciculus cuneatus end in cuneate tubercle that is wedge shaped. Hence, it is called fasciculus cuneatus. 6. Scientists who have worked on it: The posterior column tract is named Goll and Burdach because it is studied by Goll and Burdach.

Spinal Cord

21

,

'

Note: Please do watch video of animation of "Nomenclature of tract" on CBSiCentral App. Reference -Animation video B/3 Duration: 3.20 minutes

\.

SN-11

How the ascending tracts are grouped?

Grouping of tracts 1. Ascending tracts can be grouped as tracts reaching up to

A. Thalamus, and

co

B. Cerebellum. A. All tracts reaching the cerebrum must first reach thalamus except olfactory tract. The tracts reach in VPL nucleus of thalamus. VPL is Ventro-Postero-Lateral

I+--

I

VPL begins with the name of the nucleus of thalamus. The 1st letter of tract ending into VPL nucleus of thalamus. Ventral spinothalamic tract Posterior column, and

Lateral spinothalamic tract. B. Tracts reaching up to cerebellum are a. Anterior spinocerebellar tract, and b. Posterior spinocerebellar tract. Note: Please do watch video of animation of "grouping of tracts" on CBSiCentral App Reference -Animation video B/4 Duration: 2.56 minutes

SN-12

C

ro ,_

How the descending tracts are grouped?

Descending tracts are divided into 1. Pyramidal, and

2. Extrapyramidal. 1. Pyramidal tracts begin from pyramidal cells of cerebral cortex and form decussation which resembles a pyramid. They include a. Corticospinal, and b. Corticonuclear tracts. 2. Extrapyramidal tracts arise other than pyramidal cells of cerebral cortex. They arise from basal nuclei or nuclei of brainstem and reach spinal cord.

22

C:

C1l ,_

c::o

I

Exam-Oriented Anatomy

ox 3.1 Please note, 1. The fibres of extrapyramidal tract do not pass through the pyramid of medulla. They are not direct fibres from cerebral cortex to anterior horn cells of spinal cord. Hence, they are called indirect corticospinal tract. 2. Most important extrapyramidal tracts are A. Reticulospinal, and B. Vestibulospinal tracts. 3. The other extrapyramidal tracts are A. Rubrospinal, B. Reticulospinal, C. Tectospinal, D. Vestibulospinal, and E. Olivospinal. Box 3.2

Honorable Padmashree, Late Dr Mahdi Hasan, used the following easy method to remember the names of extrapyramidal tract: He used to say, "The letter "P" indicates pyramidal. • After "P," drop the next alphabet "Q". • The letter "Q" is followed by the letter "R" • Pick up the alternate alphabet after "R". • Each alternate letter after the letter "P" gives the name of the tract. • They are "T" and "V". • The letters "R", "T" .and "V" indicate -

"R" -Rubrospinal, Reticulospinal "T" -Tectospinal "V" -Vestibulospinal "P" is preceded by "O" which indicates Olivospinal

Spinal Cord

SN-13

23

Draw and label a transverse section of spinal cord showing external features. Posterior

+

Anterior ~ - - - - - - - Posterior median sulcus

Posterior funiculus----;;'----(column)

C

ro ,_

co

Lateral funiculus-\5: (column)

Horn of grey matter

0

+----+-___,__ _

Anterior funiculus------>.~ (column)

~-~

~ f - - -1F--~ ~ L . . . . __ _ _

Anterior Ventral median fissure

Fig. 3.7: TS of spinal cord showing external features

SN-14

Draw and label a transverse section of spinal cord showing grey matter.

Posterior

+

Anterior

Fig. 3.8: TS of spinal cord showing grey matter (sensory and motor nuclei)

SN-15

Draw and label a transverse section of spinal cord showing main ascending and descending tracts.

24

I

Exam-Oriented Anatomy

Posterior

+

Anterior

Gracilis Fasciculus ~ uneatus - + - - -~

111111.\---W\ Dorsa= Spinocerebellar

I-

C: C1l ,_

c::o

tract

Ventral

f---irvPL 1. Ventral spinothalamic tract 2. Posterior column 3. Lateral spinothalamic tract

Fig. 3.9A: TS of spinal cord showing positions of ascending tracts

Posterior

+

Anterior

Lateral cort1cospinal tract Rubrosp1nal tract

Ret1culosp1nal tract Vestibulospinal tract

\

0

~ ..,

~

I

E-----+-----,,--Tectospinal tract _AiiiiF:,. L - - -

Ventral corticospinal tract

I■

Motor nuclei I

Fig. 3.9B: TS of spinal cord showing positions of descending tracts

SN-16

Lateral lemniscus

1. Definition: It is bigger bundle of white matter forming auditory pathway. 2. Features A. It is 3rd order neuron of auditory pathway. B. It starts from superior olivary nucleus. C. The fibres decussate and go to opposite side of dorsal part of pons. D. It forms trapezium a shaped structure called a trapezoid body. E. It terminates at inferior colliculus of midbrain.

Spinal Cord

25

F. It reaches medial geniculate body through inferior brachium. G. The nucleus of the lateral lemniscus consists of small groups of neurons (18,000 to 24,000). 3. Relations: It is located very close to the inferior colliculus. SN-17

Medial lemniscus

Introduction: It is a bigger bundle of the axons, which arises from gracile and cuneate nuclei. It consists of 2nd order sensory neurons. 1. Course: Their axons cross the midline. They run ventrally and medially. They are called internal arcuate fibres. The crossing fibres of the two sides constitute the ~ sensory decussation. co Note: Please do watch video of animation of "Course of medial lemniscus" on CBSiCentral App. Reference -Animation video B/8 Duration: 4.08 minutes 2. Formation: It is formed by A. The fibres of the 2nd order neurons of posterior column, and B. The fibres of the anterior spinothalamic tract. Please refer Fig. 3.3. Formation of medial lemniscus (OLA-6). 3. Location: It is formed in the middle of the medulla oblongata. 4. Representation A. Somatotopic representation Table 3.2: Somatotopic representation

Event

Upper limb

Lower limb

• Before sensory decussation or before formation of medial lemniscus

• Laterally

• Medially

• After sensory decussation or after formation of medial lemniscus

• Posteriorly

• Anteriorly

B. Modality representation: The fibres are arranged in the posterior column. They are arranged from dorsal to ventral as follows Pressure, Vibration, Movement, Position, and Touch. The touch fibres include I. Tactile localization, II. Tactile discrimination, and III. Stereognosis.

I.._ P ViM Pis Touch!.

2s I

Exam-Oriented Anatomy

Posterior

+

Anterior

ell.

, i 17 T~2 L3SS,--_ _ _ Pressure Vibration Movemen Position Tou ch

0

C:

C1l ,_

c::o

S - Sacral L - Lumbar T - Thoracic C - Cervical

Fig. 3.10: General segmental and modality arrangement of fibres in dorsal column

5. Position of medial lemniscus at different levels Table 3.3: Position of medial lemniscus at different levels

Site • Upper part of medulla • Pons • Midbrain • Thalamus

I

Position • Medially and dorsally • Tegemental part • VPL -Ventro-Postero-Lateral

6. Applied anatomy ► ►

Lesion before formation of medial lemniscus: Loss of conscious proprioceptive sensations on the same side. Lesion after formation of medial lemniscus: Loss of conscious proprioceptive sensations of the opposite side. Describe extrapyramidal tracts under following heads 1. Tracts, 2. Functions, and 3. Features

Definition: Fibres passing from the cerebral cortex to spinal cord via other parts of the cerebrum, and nuclei of brainstem are called extrapyramidal tracts (Fig. 3.11). 1. Through extrapyramidal tracts, the cerebral cortex has indirect effects on the motor

cells of the brainstem, and spinal cord.

Spinal Cord

27

A. These pathways form part of an extensive system, known as the extrapyramidal system. B. Since these pathways do not pass through the pyramid in the medulla oblongata, they are called extrapyramidal tracts. They are also called indirect corticospinal tract. C. The most important extrapyramidal tracts are a. Rubrospinal

b. Tectospinal c. Reticulospinal I. The lateral reticulospinal tract arises from the medullary part of the reticular formation. The fibres course through the lateral white column. They are c ro ,_

Superior

co

Right + Left Inferior I

Red nucleus-~-Midbrain Lateral reticular nuclei---;-- - ~ ,

\ )

Pons--+

Vestibulospinal tract

Lateral reticulospinal tract

Medulla--....,

Tectospinal tract -

Medial reticulospinal tract Vestibular nuclei

----+-----""11

H----- - -

Rubrospinal tract

Spinal cor,1-----+1

Fig. 3.11 : Extrapyramidal tract

2a

C:

C1l ,_

c::o

I

Exam-Oriented Anatomy

largely intermingled with corticospinal fibres. Its influence on anterior horn cells is facilitatory. IL The medial reticulospinal tract comes from cells in the pontine reticular formation. It descends in the anterior white column, to have an inhibitory action on motor neuron. d. Vestibulospinal tracts: The lateral vestibulospinal tract arises from the lateral vestibular nucleus present in the medulla. It runs down the cord approximately in the region of anterior nerve root region. The vestibulospinal tract primarily affects trunk and limb girdle musculature. It is of great importance for posture and balance. The reticulo- and vestibulospinal fibres synapse with intemeurons which in tum project to the motor neurons. 2. Functions: They are mainly concerned to regulate the tone and posture. It involves complex movements of more automatic nature, such as the A. Maintenance of balance during movements, B. Right muscle tone is necessary for normal movements, etc. The corticospinal and rubrospinal tracts are described as being facilitatory to flexors and inhibitory to extensors, while the vestibulospinal tract is said to have the opposite effect. The medial reticulospinal tract is generally regarded as facilitatory and the lateral tract as inhibitory. Note: We use rubrospinal tract while sitting. We use vestibulospinal tract while standing. 3. Features A. Extrapyramidal fibres end in relation to gamma neurons. They are present in anterior horn cells of spinal cord. B. The control of extrapyramidal system is in premotor area no. 66. It is situated in posterior parts of superior, middle and inferior frontal gyri. Describe corticospinal tract or pyramidal tract under following heads 1. Origin, 2. Course, 3. Termination, and 4. Applied anatomy

1. Origin A. Types of cells: The axons of the pyramidal tract arise from pyramidal cells of cerebral cortex. B. Area of origin of fibres a. One-third fibres arise from upper two-thirds of precentral gyrus (area no. 4). b . One-third fibres arise from premotor cortex (area no. 6). c. One-third fibres arise from post central gyrus (somatosensory cortex area 3, 1, 2). d . Remaining fibres arise from adjacent parietal cortex (area no. 5).

Spinal Cord

29

C. Types of fibres: Myelinated and relatively low conducting small fibres. D. Distribution of fibres: a. 55% of the corticospinal fibres are concerned with the muscles of the upper limb. b. 20% fibres are concerned with the muscles of the trunk. c. 25% fibres are concerned with the muscles of the lower limb. 2. Course: After arising from different areas of cerebral cortex, they pass through A. Corona radiata of cerebral cortex. B. Anterior two-thirds of posterior limb of internal capsule. C C. Middle two-thirds of ems cerebri of cerebral peduncle of midbrain. ro ,_ co D. Basilar part of pons through pontine nuclei. E. Anterior part of medulla oblongata. a. The fibres start decussating in the upper part of medulla oblongata and decussation is completed at lower of medulla oblongata. b. The crossing of fibres forms a bulging which resembles a pyramid. c. Each pyramid contains about a million axons of varying diameter. The majority are myelinated. The diameter varies. I. Most have a diameter of 1-4µ. IL 10% have diameters of 5-10µ. III. Very few have 11-22µ. The largest diameter axons arise from giant pyramidal neurons. F. Ninety percent or fibres decussate and travel through lateral column of spinal cord and hence called lateral corticospinal tract. Almost 98% fibres end by synapsing with intemeurons, which in tum project to alpha and gamma motor neurons of the anterior horn. The 2% fibres that synapse directly with motor neurons are those which originate from the giant Betz cells.

Note: Please do watch video of animation of "Course of corticospinal tract" on CBSiCentral App. Reference -Animation video C/11/2 Duration: 4.59 minutes 3. Termination A. Details of termination

a. b. c. d.

Most of the fibres terminate contralaterally on intemeurons in the Lateral parts of lamina of IV-VI of spinal grey matter. Both medial and lateral parts of laminae VIL These fibres are connected to the alpha and gamma motor neurons of the lamina IX.

e. Fibres from frontal cortex, terminate mostly on intemeurons in laminae V-VIII.

30

I

Exam-Oriented Anatomy

s+, Inferior

§9

t\W~

C: C1l ,_

c::o

Midbrain

Posterior

+

Anterior

Medulla

Spinal cord

~-+-T- --> ..,._,+ ~ ~

i ~

Fig. 4.6: Accommodation reflex

Box4.2 Note that the pretectal nucleus is not involved in the accommodation reflex.

sa

I

Exam-Oriented Anatomy

Applied anatomy : In lesions of the pretectal nucleus, the light reflex is lost, but the pupil contracts on accommodation. This is called the Argyll-Robertson p upil (accommodation reflex present-ARP). SN-34

Pathway of hearing (auditory pathway)

1. The 1st order neurons are located in the spiral ganglion. They are bipolar cells.

The peripheral processes innervate the organ of Corti, while the central processes terminate in the dorsal and ventral cochlear nuclei. 2. The 2nd order neurons lie in the dorsal and ventral cochlear nuclei. Most of the C: axons arising in these nuclei cross to the opposite side (in the trapezoid body A ) C1l ,_ and terminate in the superior olivary nucleus. (Many fibres end in the nucleus of c::o the trapezoid body a or of the lateral lemniscus). Some fibres are uncrossed. 3. The 3rd order neurons lie in the superior olivary nucleus present in the pons. The axons form the lateral lemniscus and reach the inferior colliculus. 4. The 4th order neurons lie in the inferior colliculus. Their axons pass through the inferior brachium to reach the medial geniculate body. (Some fibres of the lateral lemniscus reach the medial geniculate body without relay in the inferior colliculus.) 5. The 5th order neurons lie in the medial geniculate body. The axons form the auditory radiation, which pass through the sublentiform part of the internal capsule to reach the auditory area of the temporal lobe. Posterior

+

Anterior Medial geniculate body (5th order neuron)

Lateral lemniscus -------+

Ventral cochlear nucleus

Dorsal cochlear nucleus

Nucleus of trapezoid body (3rd order neuron)

l

Fig. 4.7: Auditory pathway

1st order neuron

2nd order neuron

CHAPTER

5 Brainstem

f'&-J·• Draw and label ventral surface of the brainstem. Refer Fig. 5.1

1r4~11,■ Pyramidal decussation Introduction: It is a crossing of corticospinal fibres at the level of medulla oblongata (Fig. 5.2). 1. Origin: Corticospinal fibres arise from the area no. 4, 6, 8 of precentral gyrus and from area no. 3, 1, 2 of postcentral gyrus. 2. Location: On the anterior surface of medulla oblongata. 3. Features A. The corticospinal fibres cross at medulla oblongata. It forms a bulging which resembles pyramid. B. The decussation starts at upper part of medulla and completed at lower part of medulla. C. The 80% fibres cross at medulla oblongata and 20% fibres cross at the respective region of spinal cord. D. The crossed fibres course through lateral column and is called lateral corticospinal tract. E. The uncrossed fibres traverse through the anterior column and are called anterior corticospinal tract. F. Pyramidal tract fibres are composed of a. 55%-upper limb b. 25% -lower limb c. 20%-trunk 4. Termination: The crossed fibres continue in the lateral column of the opposite side as lateral corticospinal tract. These fibres terminate in the laminae IV to VII of spinal grey matter. They are connected to the alpha and gamma motor neurons of the lamina IX through the intemeurons. 5. Effect of decussation A. It displaces the central grey matter and central canal dorsally. 69

Optic chiasma

Cranial root of accessory nerve

Vagus nerve

-

/

:+--

~

, C

Hypoglossal nerve

Vestibulocochlear nerve

Abducent nerve

Sensory nerve

Trigeminal nerve

Trochlear nerve

Oculomotor nerve

Optic nerve

B. Showing exit of cranial nerves

,,,

Inferior

s:r

Fig. 5.1: Brainstem (viewed from ventral surface)

I ■ Mixed nerve

■ Motor nerve

~

Facial nerve -------,L--~ Glossopharyngeal nerve

■ Sensory nerve

..,_____ Inferior cerebellar peduncle

Olive

' - - Basis pedunculi of midbrain

" - ~ Optic tract

,,----------- Tuber cinerium \ with infundibulum

A. Showing features of brainstem

Middlecerebellar peduncle

Posterior ---i{'---+/--__..,,. perforated substance

Mammillary body

Inferior

+

Superior

Brain

'


coC.

::,

co·

Q

m

s3

~

Brainstem

71

B. The continuity between the ventral grey column and central grey matter of the spinal cord is lost. C. The column subdivides into the supraspinal nucleus, and the nucleus of the accessory nerve. D. The anterior median fissure is interrupted by the pyramidal decussation. 6. Applied anatomy : Lesions of the corticospinal tract is called the upper motor neuron

lesion. ► The lesion above the level of pyramidal decussation results in paralysis of the muscles of the upper limb and lower limb on opposite side of the body. c ► The lesion below the level of pyramidal decussation results in the paralysis of ~ the muscles on the same side of body. co Dorsal

+

Ventral

Lateral corticospinal tract

Fig. 5.2: Pyramidal decussation

SN-35

Blood supply of medulla oblongata

1. Arterial supply (Figs 5.3A and B)

A. Branches of vertebral artery

a. Anterior spinal artery b. Posterior spinal artery c. Posterior inferior cerebellar artery 1(..... PICA) I B. Branches from the basilar artery a. Medullary branches, and b. Anterior inferior cerebellar artery.

12

I

Exam-Oriented Anatomy

2. Venous drainage : It is divided into lower and upper parts of medulla oblongata. A. Veins of lower part of medulla penetrate deeper regions. They open into anterior and posterior spinal veins. B. Veins of the upper part of medulla drain into sigmoid or petrosal sinus.

Posterior

+

Superior

+

Anterior C:

Inferior

C1l ,_

c::o

Vertebral artery

++-----+- Area supplied by anterior spinal artery branch of vertebral artery

Fig. 5.3A: Arterial supply of medulla at motor decussation

Fig . 5.38 : Arteries supplying medulla oblongata

Posterior

+

Anterior

Hypoglossal nucleus----+>_ _ _ _______., Hypoglossal nerve--;------

------h~■

Medial lemniscus -\-/

Olive

\

- - - - - - - + - Area supplied

by anterior spinal artery branch of vertebral artery

■ Sensory

■ Motor

Fig. 5.4: Blood supply of medulla at sensory decussation

Draw and label a transverse section of medulla oblongata at the level of pyramidal decussation.

Brainstem

73

Posterior

+

Anterior ~ , - - - - - - - - - - Nucleus gracll1s Nucleus cuneatus

□o;: ~:"~ t~'.~

of trigeminal

•

0

C

ro ,_

co

Motor nucleus ~ of 12th nerve

Motor nucleus of 9th nerve

\

Fig. 5.5A: TS of medulla oblongata showing grey matter at pyramidal decussation Posterior

+

Anterior

Spinal tract of trigeminal nerve Dorsal and ventral spinocerebellar tract Lateral spinothalamic tract ■ Sensory (ascending tract)

■ Motor (descending tract)

.

~

Vestibulospinal tract Rubrospinal tract

~ - - - - - - Ventral (anterior) spinothalamic tract

Fig. 5.58: TS of medulla oblongata showing white matter at pyramidal decussation

SN-36

Arcuate fibres

Introduction: The axons of various nuclei are arranged like the arc. 1. Types: These are A. Internal arcuate fibres: a. These are 2nd order neurons arising from gracilis and cuneatus nuclei. The nuclei situated on dorsal side of medulla.

Exam-Oriented Anatomy

74

b. These fibres cross to the opposite side and form medial lemniscus. c. Somatotopic arrangement: L Before decussation i. The fibres of lower limb are placed medially. ii. The fibres of upper limb are placed laterally. II. After decussation i. The fibres of the lower limb are placed anteriorly. ii. The fibres of the upper limb are placed posteriorly. C:

C1l ,_

Posterior

c::o

+

Anterior

~ -- - -- - Nucleus gracilis Fasciculuj C unea t us ~ - - - - Nucleus

Accessory - ----==t'--t+_ cuneate nucleus

~~--

~ - -- - Posterior external arcuate fibres

Cerebellum

,,.__ _ _ _ Anterior external arcuate fibres

Fig. 5.6: Arcuate fibres

B. External arcuate fibres: These are of following types a. Anterior external arcuate fibres: L These fibres arise from arcuate nuclei present on the anterior surface of medulla oblongata. They reach the nuclei of the same side of cerebellum. IL Function: They convey information from cerebrum to cerebellum. The cortico-arcuato-cerebellar pathway is functionally equivalent to corticoponto-cerebellar pathway. b. Posterior external arcuate fibres (cuneocerebellar) L These fibres arise from accessory cuneate nucleus and reach the nuclei of cerebellum on the same side. IL Function: These are homologous of posterior spinocerebellar tract in upper limb and carries unconscious proprioceptive sensations from upper limb. 2. Applied anatomy : Following are the effects of lesion of internal arcuate fibres. ► ►

Before decussation: Loss of sensation of touch and pain on the same side. After decussation: Loss of touch and pain on the opposite side.

Brainstem

75

Draw and label a transverse section of medulla oblongata at the level of sensory decussation. Posterior

+

Anterior

'\

J.- /0... \ ~:;: '~~:~~"' ~

e\

...._..,-~c

,D ~

I;

Nucleus gracilis Nucleus cuneatus

i )~ :~:.:' "'"' · ~

12th oeNeoocleos

. - - - Medial lemniscus

_ ___;~-::r-----

Arcuate nucleus

Fig. 5.7A: TS of medulla oblongata at sensory decussation showing grey matter Posterior

+

Anterior

....... VPL 1. Ventral spinothalamic tract 2. Posterior column 3. Lateral spinothalamic tract ■

Spinocerebellar tracts

Sensory (ascending tract)

■ Motor (descending tract)

Anterior - - - - - - - -~ corticospinal tract

'---,''----- Rubrospinal tract ' - - - - - - - Vestibulospinal tract

Fig. 5.7B: TS of medulla oblongata at sensory decussation showing white matter

£

1s I

Exam-Oriented Anatomy

Draw and label a transverse section of medulla oblongata at the level of inferior olivary nucleus or pontomedullary junction.

Posterior

+

Anterior

s:.-~ .. ~• /

Vestibular n u c l e i - - - - ~ - ~

. , ~- ~

Dorsal nucleus

~ ~ - - - - - + - - vagus-motor

C:

£

\

Nucleus ambiguus

••

nucleus+e •

Spinal of trigeminal nerve

a.____

~

-

•

12th nerve nucleus

)

~ Nucleus of

)

(

Dorsal accessory

•

~

tractus solitarius

•

'"""' ""'' "' ( ~ I ' .._

Ollvary nucleus ~

~

•

a...

Arcuate n u c l e u s - - - - - ~ ~~

~

~

Medial accessory

'"""' ""''·"'

■ Sensory (ascending tract)

■ Motor (descending tract)

.,.

Fig. 5.8A: TS of medulla oblongata at inferior olivary nucleus showing grey matter Posterior

+

Anterior

Inferior cerebellar peduncle

[ ,-~ ~-l K

Medlallemols'"s

Ventral spinocerebellar - - - ' tract

Olivocerebellar - - - + - decussation

/

~

Motor (descending tract)

)

'

R,bcosploal tcaci

J

Lateral spinothalamictract ---,'-------Corticospinal tract

~

■ Sensory (ascending tract) ■

'

-

-

Fig. 5.8B: TS of medulla oblongata at inferior olivary nucleus showing white matter

Brainstem

77

Posterior

+

Anterior

lcfe,lm

cernbella,---11 peduncle

Medial

,!

( •

0

lemniscus--~ --► -.---+1-I■

l

-

I

----,,-n.. nucleus lntralaminar thalamic nucleus

Inferior

---Putamen

l+f------Strionigral

1+------Nigrostriate

Posterior

+

Anterior

Pars compacta

Fig. 8.26: Connections of neostriatum

a. Connections of paleostriatum (Fig. 8.27) Table 8.13: Afferent connections of the paleostriatum

Fibres

Origin

Destiny

• Striatum

• Putamen

• Globus pallidus

• Pars compacta of substantia nigra

• Substantia nigra

Cerebrum

141

Caodate oode,sj Striopallidal Ansa lenticularis--t-+ / Medial thalamic nucleus lntralaminar thalamic--+s-•1 nucleus

Globus pallidus

+--+--- Puta men

s+, Inferior

11++- + - - - - Fasciculus sub-thalamicus -

-

--Nigropallidal

C

ro ,_

Subthalamic nucleus

co

- ~- - + - - - - Descending pallidotegmental brain

Posterior

+

Anterior

Fig. 8.27: Connections of paleostriatum Table 8.14: Efferent connections of paleostriatum

Fibres

I Origin

• Fasciculus lenticularis

• Inner segment of globus pallidus

• Ansa lenticularis

• Both segments of globus pallidus join with dentatorubrothalamic fibres

• Fasciculus subthalamic • Descending pallidotegmental

• Globus pallidus.

I

Destiny -

• Thalamus - Ventroanterior, - Ventrolateral and - Centromedian nuclei of thalamus • Subthalamic nuclei • Red nucleus • Reticular nuclei of midbrain • Inferior olivary nucleus

3. Functions: Basal nuclei are considered as important parts of the extrapyramidal system. They control A. Planning and programming of movements. a. Reflex and voluntary muscular activity. b. Skilled and manipulative movements of the body, e.g. threading a needle. B. Automatic associated movements as coordinated movements of legs or swinging of arms during walking. C. Abnormal involuntary movements. D. Movements of emotional expression.

Exam-Oriented Anatomy

2. Applied anatomy : In lesions of basal ganglia, abnormal manifestations are observed. They are of two types. ► Hypertonic and hypokinetic: Increased muscle tone without alterations of deep reflexes, e.g. Parkinson's disease (paralysis agitans). It is characterised by • Rigidity and tremors. Rigidity is due to increased muscle tone. • It affects all muscles with poor movements. It results into cogwheel rigidity. • Patient has masked face appearance with no emotional response. • He walks with short and shuffling gait (quick steps). • He experiences difficulty in taking initial steps and in terminating movements. C: C1l • Tremors occur with regular frequencies when subject is at rest. Tremors ,_ c::o disappear during movements. They increase in emotions. ► Abnormal involuntary movements or dyskinesis are in the form of • Athetosis: Slow, worm-like writhing movements of extremities, affecting chiefly fingers and the wrist. It is seen due to damage of putamen. • Ballismus (Gr. jumping about, dancing): It is a rare disease manifested by wild, flail-like movements of one arm and is caused by degeneration of subthalamic nucleus of opposite side. • Chorea (Gr. dance): It is characterized by brisk, jerky, purposeless and graceful movements of the distal parts of the extremities and associated with twitching of face. They are cardinal signs of two diseases. • Sydenham's chorea: It is one of the complications of rheumatic fever. • Huntington's chorea: It is a dominant hereditary disorder. It first appears in middle age and become worse in advanced age. It results into mental deterioration. It is due to degeneration of striatum and due to reduced GABA.

,O

Table 8.15: Lesion of basal ganglion and the resulting entity

Lesion of basal ganglion

Disease (entity)

• Substantia nigra

• Parkinson's disease

• Subthalamus • Corpus stiatum-Caudate nucleus

• Hemibalismus

• Globus pallidus • Lentiform nucleus

SN-70

I

• Chorea • Athetosis • Wilson's disease

Corpus striatum

Corpus striatum: It consists of 1. Caudate nucleus, 2. Lentiform nucleus. The head of caudate nucleus and lentiform nucleus are connected by a band of white matter, situated deep to the anterior limb of internal capsule. They give the appearance of the striations as grey, white and grey. Hence, these nuclei forming the striations are called nuclei corpus striatum.

Cerebrum

143

3. The lentiform (lens shaped) nucleus has A. Medial part: It is called globus pallidus. B. Lateral part: It is called putamen (shell). The caudate nucleus and putamen are called neostriatum. Globus pallidus is called paleostriatum.

1•)t;j4'j Name the parts of the caudate nucleus 1. Head, 2. Body,and 3. Tail.

C

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co

SN-71

Caudate nucleus

(Caudate-tail) 1. Definition: It is a large mass of grey matter situated deeply within the cerebral hemisphere. It forms part of the basal nuclei and belongs to neostriatum. 2. Parts of caudate nucleus (Fig. 8.28) A. Head: It is a large, globular part, forms floor of anterior horn of lateral ventricle.

a. Situation I. It lies on medial side of anterior limb of internal capsule. II. It is separated from lentiform nucleus by anterior limb of internal capsule. III. In the upper part, it is continuous with putamen of lentiform nucleus and in the lower part it gives stripped appearance in horizontal section. Superior Anterior+ Posterior Inferior - - - - - - - - - Anterior limb +-+-~-----Genu __,_ _ _ Posterior limb - - Retrolentiform part

Body Head of caudate nucleus

of caudate nucleus

----+-+

Lentiform n u c l e u s - - - - ~ Amygdaloid nucleus -----------+1

Fig. 8.28: Parts of caudate nucleus

of internal capsule

Exam-Oriented Anatomy

B. Body Relations I. Medially: Thalamostriate groove containing i. Thalamostriate vein. ii. Stria terminalis: It is a white matter and connects amygdaloid nucleus to septal nuclei. II. Laterally: Pronto-occipital bundle above and corona radiata below. III. Posteriorly: Continuous with the tail. C. Tail: It forms roof of inferior horn of lateral ventricle and ends in amygdaloid C: C1l ,_ body. c::o Relations I. Medially: Stria terminalis. II. Laterally: Tapetum (Tapetum-carpet). III. Superiorly i. Sublentiform part of internal capsule, and ii. Globus pallidus. 3. Structure Putamen (putamen-shell): It contains mostly small stellate cells and only few large cells, whose fibres pass on to the globus pallidus. 4. Connections: Please refer connections of neostriatum. 5. Applied anatomy : In Huntington's chorea, the small cells of caudate nucleus and putamen are affected due to the disease process and there is marked decrease of GABA (gama-aminobutyric acid) in the strionigral neurons. Chorea is intermittent, brisk, jerky, purposeless involuntary movements of the distal parts of the extremities. SN-72

Amygdaloid body

Introduction: It is an almond shaped nucleus present at the end of tail of caudate nucleus. 1. Location: Temporal lobe, lying anterosuperior to the inferior horn of the lateral ventricle. 2. Topographically: It is continuous with the tail of the caudate nucleus, but functionally it is related in the stria terminalis. It is a part of the limbic system. It is continuous with the cortex of the uncus of the temporal lobe, the limen insulae and the anterior perforated substance. 3. Evolution: It is the part of archi striatum. 4. Connections (Fig. 8.29) A. Afferent: From the olfactory tract. B. Efferent: It gives rise to the stria terminalis which ends in the anterior commissure, the anterior perforated substance and in hypothalamic nuclei.

Cerebrum

145

Superior Anterior+ Posterior Inferior

C

ro ,_

Hypothalamus

co

Fig. 8.29: Main connections of the amygdaloid body

SN-73

Trigeminal nucleus Table 8.16: Parts of trigeminal nucleus and their location and functions

Particulars • Location

• Cell body

• Development • Functions

I

Spinal

• Pons to the second or third segment of spinal cord

I Sensory

!Motor

• Pons

• Pons

• Midbrain

• Motor nucleus

• Mesencephalic nucleus • It lies within CNS which is exception for its location • Mesencephalon

• Trigeminal ganglion

• Myelencephalon • Metencephalon • Touch and • Movements • Pressure from of the the skin of face muscles of and neck mastication

• Pain and temperature from the skin of face and neck

I Mesencephalic

• Proprioception from - Muscles of mastication - Facial expression - Musclesofeyeball and - Temporomandibular joint Contd.

Exam-Oriented Anatomy Table 8.16: Parts of trigeminal nucleus and their location and functions (Contd.)

C:

C1l ,_

c::o

Particulars

Spinal

Sensory

Motor

• Lesion

• Loss of touch • Loss of pain and temperature and pressure from the skin from the skin of the face on of the face on the side of lesion the side of lesion

• Homologous tract in the limbs

• Lateral spinothalamic tract

Mesencephalic

• Paralysis of • Loss of proprioception muscle of mastications on the side of lesion

• Anterior • Corticospinal • Posterior tract column spinothalarnic tract

if4½J• Define and classify white matter of cerebrum. 1. Definition: These are myelinated fibres, which connect various parts of the cortex

on the same side, opposite side and also other parts of the central nervous system. 2. Classification: It is classified as, A. Association fibres: They connect gyros of the same side of the cerebral hemisphere (Fig. 8.30). They are a. Short association fibres: They connect the different areas of the same gyrus or adjacent gyri, e.g. superior frontal gyrus to inferior frontal gyrus. b. Long association fibres Table 8.17: Examples of long association fibres

Particulars

Connects

To

• Superior longitudinal fasciculus

• Frontal lobe

• Occipital and temporal lobe

• Inferior longitudinal fasciculus

• Occipital lobe (areas 18 and 19)

• Temporal lobe

• Uncinate fasciculus

• Broca's area and gyri on the orbital surface of frontal lobe

• Temporal lobe

• Cingulum fasciculus

• Cyrus cingulurn

• Parahippocampal gyrus Superior

Posterior+ Anterior Inferior

■ Frontal~ D Parietal Lobe D Temporal D Occipital

Superioj Longitiudianal fasciculus ~--Inferior

Fig. 8.30: Superolateral surface of left cerebral hemisphere showing association fibres

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147

B. Commissural (transverse) fibres: They connect two identical/non-identical areas of one cerebral hemisphere to the other cerebral hemisphere (Fig. 8.31). It may be C. Homotypical: It connects two identical areas. D. Heterotypical: It connects two non-identical areas. E. Examples a. Corpus callosum: It is the biggest bundle of commissural fibres and connects frontal, temporal and occipital lobes. b. Anterior commissure: Round bundle of white matter formed by L Archipallial (archi-cortex) belongs to rhinencephalon and connects shaped ~ olfactory bulb and piriform area of both sides. It is pear paleocortex present on the anterior part of parahippocampal gyrus. co IL Neopallial: It is a larger bundle and connects two temporal lobes. c. Posterior commissure: It connects superior colliculi of both the sides and transmits L Corticotectal fibres, IL Pretectal fibres. d. Hippocampal commissure: It is present at the junction of the posterior columns of fomix. It connects hippocampus of both sides. e. Habenular commissure: It connects habenular nuclei present in the habenular It is responsible for visceral response to basic emotional drives and olfactory impulse.

6

!·

Posterior thalamic nuclei

Posterior commissure 1+------Pretectal nucleus

Fig. 8.31: Commissural fibres

C. Projection fibres: These are afferent and efferent fibres of cerebrum. They are present in the internal capsule and fornix. a. Afferent L Thalamocortical, IL Auditory radiation, and III. Visual radiation.

1481

Exam-Oriented Anatomy

b. Efferent I. Corticobulbar or corticonuclear, II. Corticospinal, and III. Corticopontocerebellar.

1•)!$.j ■ Name the parts of the corpus callosum. 1. Genu is the anterior end. It lies 4 cm behind the frontal pole.

2. Rostrum is directed downwards and backwards from the genu. It ends by joining the lamina terminalis. c: 3. Trunk or body is the middle part, between the genu and the splenium. Its superior ~ surface is convex from before backwards and concave from side-to-side. It is c::o overlapped by the cingulate gyrus and is covered by the indusium griseum and the longitudinal stria. The inferior surface is concave from before backwards and convex from side-to-side. 4. Splenium is the posterior end. It forms the thickest part of the corpus callosum. It lies 6 cm in front of the occipital pole.

+

Superior Posterior

Anterior

Inferior

Part of corpus callosum

I Splenium

Trunk

Rostrum Genu

I

i-~ Fig. 8.32: Parts of corpus callosum

Describe corpus callosum under following heads 1. Gross anatomy, 2. Parts, 3. Blood supply, 4. Functions.and 5. Applied anatomy.

Definition: It is the largest bundle of commissural fibres which connects the two identical areas of neocortex, except the following area. • Lower and anterior parts of the temporal lobe. They are connected by the anterior commissure.

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149

• Primary visual cortex (area 17). • Some parts of primary acoustic (area 41). • Parts of primary somatosensory area (area 2, 1) especially those for the hand and foot. • Part of the motor cortex (area 4) serving distal parts of the upper and lower limbs (excluding the shoulder and hip region). 1. Gross anatomy A. Situation: It is situated at the bottom of the median longitudinal fissure and lies nearer to frontal pole than to the occipital pole. Anterior end is about 4 cm from C frontal pole whereas posterior end lies about 6 cm from occipital pole. ro ,_ B. Length: 10 cm. co C. Type: Neopallial commissural fibres 2. Parts: It has four parts (Fig. 8.33).

+

Superior Posterior

Anterior

Inferior Cingulum _ _ _ _....,,...,:::.. Trunk -----7""--------:::::,--"

Fornix

Callosal sulcus - - -- ---+--+---1-

Splenium -+-~,.,.

Gen u Rostrum ~

-

- - - - - - Anterior commissure 1+-------

Lamina terminalis

Fig. 8.33: Corpus callosum and its parts

A. Rostrum: It extends from genu to lamina terminalis.

a. Fibres: They connect the orbital surfaces of frontal lobe (Fig. 8.34). b. Relations I. Upper surface i. In the median plane, attachment of septum pellucidum, and ii. On each side forms floor of anterior horn of lateral ventricle. IL Inferior surface i. Indusium griseum, ii. Medial and lateral longitudinal striae. B. Genu: It is bend and thick part of corpus callosum. It is situated anteriorly and continues above and behind as trunk and below it continues as rostrum. Fibres: They connect medial and lateral surface of frontal lobe. These fibres are called forceps minor.

Exam-Oriented Anatomy

Anterior

+

Posterior

l+--~----'-c------

Medial and lateral surface of frontal lobe Forceps minor

~

-----+--+--- - - - - - \ - - - Transverse fibres C: C1l ,_

----+---Temporal lobe

c::o

---+-+-- , - - - - - - + - - Trunk

-----;--------;---- Tapetu m (Carpet)

,+--_________,____ Focceps majoc

~

Fig. 8.34: Fibres of corpus callosum

C. Trunk or body: It is major part of corpus callosum present between genu and splenium. It isl" wide.

a. Fibres I. They connect the two temporal lobes.

IL Tapetum (tapetum-carpet) i. It is formed by posterior fibres of trunk and anterior fibres of splenium of corpus callosum. ii. These fibres run horizontally and do not intersect to the vertical running fibres of corona radiata. iii. They form following walls of various horns of lateral ventricle.

- Roof and lateral wall of posterior horn. - Lateral wall of inferior horn. b. Surfaces: It has two surfaces I. Superior

i. It forms the floor of median longitudinal fissure. ii. It is related to anterior cerebral vessels and lower border of falx cerebri and inferior sagittal sinus.

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151

iii. It is covered by indusium griseum and medial and lateral longitudinal striae. iv. It is overlapped by cingulate gyrus but separated by callosal sulcus. II. Inferior: It forms roof of the body of lateral ventricle. It gives attachment to the following structures. i. Anteriorly and inferiorly, it gives attachment to septum pellucidum. ii. Posteriorly, it gives attachment to fornix and hippocampal commissure. D. Splenium: It is posterior and the thickest end of corpus callosum. a. Fibres: They connect the right and left occipital lobes. These fibres are called forceps major. b. Relations I. Superiorly i. It is covered by indusium griseum. ii. It is related to inferior border of falx cerebri which contains inferior sagittal sinus. iii. It is covered by cingulate gyrus on each side. IL Inferiorly: Formation of straight sinus. 3. Blood supply A. Arterial supply a. Rostrum is supplied by central branches of anterior cerebral artery. b. Genu and trunk are supplied by frontal branch of anterior cerebral artery. c. Splenium is supplied by posterior cerebral artery. B. Venous drainage : It is drained by a. Anterior cerebral vein drains into basal vein. b. Choroid vein joins with thalamostriate vein and opens internal cerebral vein. 4. Functions A. Transfer of learning process: The secondary sensory area receives input, interprets and sends copy to the opposite cerebral cortex. The information is processed and stored in the form of memory through corpus callosum. B. Transfer of speech function. C. It possibly helps in coordination of activities of two cerebral hemispheres, but congenital absence of corpus callosum does not cause any functional disturbance.

5. Applied anatomy ►

► ►

A lesion of the splenium of the corpus callosum affects the transfer of information from the right visual association cortex to the left side. Patients with a lesion of the corpus callosum responds as if he or she has two separate brains called 'split brain'. The section of the corpus callosum has been attempted surgically to prevent the spread of seizures from one hemisphere to the other.

c ro ,_

co

Exam-Oriented Anatomy

Describe internal capsule under following heads 1. Gross anatomy, 2. Fibres, 3. Blood supply, and 4. Applied anatomy.

Definition: It is a narrow gate, consists of compact bundle of ascending and descending fibres which connects the cerebral cortex to the brainstem and spinal cord (Fig. 8.35). c: 1. Gross anatomy C1l ,_ A. Communication: It continues c::o a. Above as corona radiata. b. Below as cerebral peduncle. B. Shape: In horizontal section, it appears 'V' shaped mass. C. Parts and boundaries a. Anterior limb: Lies between head of caudate nucleus and lentiform nucleus. b. Posterior limb: It is related medially to thalamus and laterally to lentiform nucleus. c. Genu (bend part of internal capsule): It is present between anterior and posterior limb. Anterior Lateral +

Medial

Posterior

'' ' '' ' ''

Frontopontine fibres - - - - - -Anterior thalamic - - - - - ---+, radiation

Anterior limb of internal capsule Corticorubral fibres -

-

~ ---

---.1

-· """

Corticonuclear fibres +----1---- Superior thalamic radiation

~..,_F--+------f-4~--+....~E:::+---t---t--Corticospinal fibres -+-----+---Posterior limb of internal capsule

Auditory radiation----~,

Retrolentiform part of internal capsule

Media'7 Geniculate body

Optic radiation-----

--•

~----LateraJ

Fig. 8.35: Internal capsule and its parts

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153

d. Retrolentiform part: It is present behind lentiform nucleus. e. Sublentiform part: It lies deep to lentiform nucleus. Note: Please do watch video of animation of "Parts of internal capsule" on CBSiCentral App. Reference -Animation video A/2 Duration: 1.56 minutes

2. Fibres Table 8.18: Parts of internal capsule and fibres present in it

Parts

I

Descending tract !

I

Ascending tract i

• Anterior limb

• Frontopontine fibres

• Anterior thalamic radiation (from anterior and medial nucleus of thalamus)

• Genu

• Corticonuclear fibres and • Corticoreticular fibres

• Anterior part of superior thalamic radiation (from posterior ventral nucleus of thalamus)

• Corticospinal tract • Parietopontine • Corticorubral

• Superior thalamic radiation • Thalamocortical fibres from • Ventroposterolateral nucleus to post-central gyms

• Posterior limb - Anterior 2/3rd - Posterior I/3rd

Table 8.19: Retrolentiform and sublentiform parts of the internal capsule and the tracts present in it

Particulars

I Fibres

I Tracts

• Retrolentiform part

• Occipitopontine fibres • Fibres form occipital cortex to superior colliculus and pretectal region

•

Posterior thalamic radiation made up of - Optic radiation - Visual pathway: Connections between parieto-occipital lobes to posterior part of thalamus

• Sublentiform part

• Temporopontine fibres: Interconnections between temporal lobe and thalamus

•

Auditory radiation: Inferior thalamic radiation

Note: Please do watch video of animation of "Composition of fibres of internal capsule" on CBSiCentral App. Reference - Animation video A/ 4 Duration: 7.56 minutes

C

ro ,_

co

Exam-Oriented Anatomy

3. Blood supply A. Arterial supply Table 8.20: Arterial supply to different parts of internal capsule

Particulars

I

Ventral part

• Anterior limb • Genu • Posterior limb C: C1l ,_

c::o

• Lateral striate branches of middle cerebral artery

I

Dorsal part

• Anterior cerebral artery (internal carotid artery) • Recurrent branch of anterior cerebral (Heubner artery) • Anterior choroidal artery • (internal carotid artery)

• Retrolentiform

• Posterior cerebral artery (basilar artery)

• Sublentiform

• Anterior choroidal artery (internal carotid artery)

Note: Please do watch video of animation of " Arteries of brain and internal capsule" on CBSiCentral App. Reference -Animation video A/5 Duration: 3.08 minutes

B. Venous drainage of internal capsule in following veins a. Striate veins drain into great cerebral vein of Galen. b. Anterior cerebral vein-drains into basal vein. c. Choroidal vein joins with thalamostriate vein and forms internal cerebral vein. d. Occipital sinus and transverse sinus Note: Please do watch video of animation of "Venous drainage of internal capsule" on CBSiCentral App. Reference - Animation video A/ 6 Duration: 1.42 minutes

4. Applied anatomy ►

► ►

►

A small lesion in internal capsule results in widespread manifestation. The common lesion is due to cerebral haemorrhage or cerebral thrombosis. It results in complete paralysis of the opposite side of body. If the posterior part of intenal capsule is involved, there will be hemianaesthesia. There is homonymous hemianopia, if the fibres of optic radiation are involved. There is aphasia, if lesion is in dominant hemisphere. The artery commonly ruptured is lateral striate artery, branch of middle cerebral artery. • It is also called artery of cerebral haemorrhage (Charcot's artery). Following are the reasons for rupture of lateral striate artery. • It is a long artery. • It is a thin artery. • It is not supported by connective tissue. • It is constantly exposed for the fluctuations of blood pressure.

Cerebrum ►

155

Capsular lesions usually are vascular due to involvement of middle cerebral artery, giving rise to hemiplegia on opposite half of body. The condition is called upper motor neuron lesion.

Note: Please do watch the video of "Applied anatomy of internal capsule" on CBSiCentral App. Reference -Animation video A/7 Duration: 4.18 minutes C

Note: Please do watch video of animation of "Introduction and objectives of internal ro ,_ capsule" on CBSiCentral App. co Reference -Animation video A/1 Duration: 5.23 minutes

(•)f+i}j What is internal capsule? The fibres descending from the various lobes of brain converge. These are called projection fibres . The to and fro fibres from the cerebral cortex to the thalamus converge and diverge. Both the sets of fibres collectively look like the sun rays and hence are called the corona radiata fibres. The area, where the fibres converge and diverge to form a compact bundle, is called the internal capsule.

(•)tffj What are parts of internal capsule? Parts of internal capsule 1. Anterior limb, 2. Posterior limb, 3. Retrolentiform part, 4. Sublentiform part, and 5. Genu. Please refer Fig. 8.28. Parts of caudate nucleus (SN-71)

(•)f+fJ ■ What are the functions of fibres present in internal capsule? Functions

A. The fibres present in the internal capsule convey general sensations like touch, pain and temperature from the lower limbs, abdomen, thorax, upper limbs, head, neck and face to thalamus. B. In addition to above sensations, it contains fibres of special sensations like vision from eyes to the thalamus; hearing from ears to the thalamus; and taste sensations from the tongue to the thalamus. C. It also consists of the descending fibres from the brain to the basal nuclei, cerebellum, and the nuclei of the spinal cord.

Exam-Oriented Anatomy

l•)f+i}j What is applied anatomy of internal capsule? Applied anatomy ► The slightest injury to the internal capsule can cause wide spread damage of the body. ► Injury to the posterior limb of the right internal capsule results in left hemiplegia. Note: Please do watch the video of "Applied anatomy of internal capsule" on CBSiCentral App. Reference - Animation video A/7 Duration: 4.18 minutes C1l ,_

c::o

Box 8.4 • Correlations of the organs of the body with the structures of the section. Symbols Tilak Eyebrows

Eyes Bridge of nose Nostril Moustaches Lower lip Ears Opening of ears Cones Dimple chin

Structures Great longitudinal fissure Genu of corpus callosum Caudate nuclei

Septum pellucidum Thalami Posterior horn of lateral ventricle Splenium of corpus callosum Insula Lateral sulcus Lentiform nuclei Great longitudinal fissure

• Associations of the areas which are not explained. Symbols Orbits Black line between green line Central line of nose "C"

Area medial to claustrum Area lateral to claustrum Areas between eyes and upper margin of cones Areas between lower margin of cones and outer margin of nostril

Structures Anterior horn of lateral ventricle Septum pellucidum Third ventricle Putamen Claustrum External capsule Extreme capsule Anterior limbs of internal capsule

Posterior limb of internal capsule Contd.

Cerebrum

157

Contd.

Bend between anterior and posterior limb of internal capsule

Genu

C

ro ,_

co

Note: Please do watch the video of animation of "Cartoon of internal capsule" on CBSiCentral App. Reference -Animation video A/8 Duration: 6.24 minutes

(•)tfj.j What are projection fibres? The fibres descending from the various lobes of brain converge. These are called projection fibres. Superior Posterior+ Anterior Inferior

Fig. 8.36: Sagittal section of brain and brainstem showing projection fibres

Exam-Oriented Anatomy

l•)f+i}j What is corona radiata? The to and fro fibres from the cerebral cortex to the thalamus converge and diverge. Both the sets of fibres collectively look like the sun rays and hence are called the corona radiata fibres.

m!IJI What are ascending fibres passing through the internal capsule and -

their functions?

1. Ascending fibres carry general sensations like touch, pain and temperature from

the (Fig. 8.37) ~ A. Lower limbs, c::o B. Abdomen, C. Thorax, D. Upper limbs, and E. Head, neck and face to thalamus. 2. Special sensations like A. Vision from eyes to the thalamus, B. Hearing from ears to the thalamus, and C. Taste sensations from the tongue to the thalamus. c:

-------Anterior thalamic radiation to frontal cortex Superior thalamic - - + - - ~ rad iation to postcentral gyrus

Fig. 8.37: Ascending fibres in internal capsule Table 8.21: Ascending fibres in internal capsule

Limb of internal capsule • Anterior limb

I

Fibres • Anterior thalamic radiation

I

Destiny • Frontal cortex

• Posterior limb

• Posterior thalamic radiation

• Post-central gyrus

• Retrolentiform nucleus

• Optic radiation

• Occipital cortex

Note: Please do watch the video of animation of "Introduction to ascending and descending fibres" on CBSiCentral App. Reference -Animation video B/2 Duration: 2.28 minutes

Cerebrum

Ill

159

What are descending fibres passing through the internal capsule and their functions and effect of lesion?

1. Descending fibres arise from the (Fig. 8.38) A. Brain, B. Basal nuclei, and C. Cerebellum. They rich to the nuclei of the spinal cord. 2. Functions: They control all voluntary muscles of the opposite side of the body. 3. Effect of lesion: The slightest injury to the internal capsule can cause wide spread c damage of the body. It results in contralateral hemiplegia. coro

Corticonuclear Corticospinal

Parietopontine and occipitopontine

Fig. 8.38: Descending fibres in internal capsule Table 8.22: Descending fibres in internal capsule

Limb of internal capsule

Fibres

Destiny

• Anterior limb

• Frontopontine

• Pontine nuclei

• Genu

• Corticonuclear

• Nuclei in the brainstem

• Posterior limb

• Corticospinal • Corticorubral

• Spinal cord • Red nucleus

• Retrolentiform

• Parietopontine • Occipitopontine

• Pontine nuclei • Pontine nuclei

Note: Please do watch the video of animation of "Introduction to ascending and descending fibres" on CBSiCentral App. Reference -Animation video B/2 Duration: 2.28 minutes

Bffll!I What is capsule? What is the basis of nomenclature of various terms -

used in relations of internal capsule?

1. Capsule: The word" capsule" is used to describe the white matter present on various

surfaces of the lentiform nucleus. Taking the lentiform nucleus as a reference point, the various terms can be explained. 2. Internal capsule: It is white matter present on the medial surface of the lentiform nucleus.

160

I

Exam-Oriented Anatomy

3. External capsule: The white matter present on the lateral surface of the lentiform nucleus. There is a grey matter lateral to the external capsule called the claustrum, which means a barrier between external and extreme capsules. 4. Extreme capsule: The white matter lateral to the external capsule is called the extreme capsule. 5. Lateral to the extreme capsule, there is another grey matter known as the insula, which literally means island. It is the 5th lobe of the brain. Superior

+

C:

Inferior

C1l ,_

c::o

Wa )"::=:::' ~

~

Internal capsule __----;/~ Thalamus Hypothalamus

.-S\

i, "xoj

i(

\

Headof caudate nucleus

/l

Claustrum lnsula

J

~\~ J Extreme

Capsule

External

Fig. 8.39: Relations of internal capsule

l•)tfj• What are relations of internal capsule? Table 8.23: Relations of internal capsule

Parts of intemal capsule

Anteriorly

Medially

Laterally

Posteriorly

• Anterior limb

• Head of caudate nucleus

• Lentiform nucleus

• Posterior limb

• Thalamus

• Genu of internal capsule • Retrolentiform nucleus

• Retrolentiform

• Lentiform nucleus

• Sublentiform

• Posterior limb of internal capsule • Head of caudate nucleus

• Genu

• Posterior horn of lateral ventricle

• Lentiform nucleus

Note: Please do watch the video of animation of "Relations of internal capsule" on CBSiCentral App. Reference -Animation video A/3 Duration: 2.06 minutes

Cerebrum

SN-74

161

What is the arterial supply of internal capsule?

Arteries of internal capsule A. The 1st and the most important group of the arteries are branches of middle cerebral artery, i.e. the lateral striate arteries. a. They pass through the anterior perforated substance. b. They course over and through the putamen of the lentiform nucleus. B. The 2nd group of arteries supplying the internal capsule is branches of anterior cerebral artery, i.e. the medial striate arteries. They course through the medial part of anterior perforated substance and pass over the medial surface of lentiform nucleus. c ro C. The 3rd artery is a branch of anterior cerebral artery, the recurrent artery ofHeubner. co a. It usually arises from Al segment of the anterior cerebral artery. b. Al segment is the portion of the anterior cerebral artery ranging between carotid bifurcation to anterior communicating artery. c. It takes a U tum after its origin, goes 'back' laterally, parallel to Al. D. The 4th artery -a direct branch of internal carotid artery-the anterior choroidal

artery. E. The 5th group of the arteries arise from posterolateral group, which are branches of

posterior cerebral artery. Table 8.24: Distribution of internal capsule

Region

I

I Ventral part (lower part)

Dorsal part (upper part)

• Anterior limb

• Recurrent branch of Huebner • Lateral striate artery, branch of middle cerebral artery

• Genu • Posterior limb • Retrolentiform part • Sublentiform part

• Direct branch of internal carotid artery • Branches of anterior choridal artery

• Branches of anterior choridal artery Anterior Right +

Left

Posterior 1+-- - - - - - A n t e r i o r cerebral artery ~ - - - - Internal carotid artery

'ri--...-----f~:!::::A - - Middle cerebral artery 0

D D D

Anterior limb Genu Posterior limb Retrolentiform

>+------+-- Anterior choroidal artery

~----'sternoclavicular joint> middle of the sternal angle >vertically up to the 4th costal cartilage. I. On the right side: It reflects vertically behind the xiphisternal joint-right costoxiphoid angle-7th costal cartilage - costodiaphragmatic line of pleura. IL On the left side: It descends close to sternum-and deviates laterally from the sternum to 4th costal cartilage-costodiaphragmatic line. b. Behind: It continues with mediastinal pleura by the side of vertebral column along a line known as the costovertebral reflection. c. Above: It continues as cervical pleura along the inner border of 1st rib. d. Below: It continues as the diaphragmatic pleura. B. Diaphragmatic pleura: It covers the thoracic surface of the corresponding part of diaphragm. Laterally, it continues as the costal pleura. Medially, it continues as mediastinal pleura. C. Cervical pleura: It extends from the inner border of 1st rib to the apex of the lung. It continues medially with mediastinal pleura. The summit of the cervical pleura is 3 to 4 cm above 1st costal cartilage. It does not extend above upper border of neck of 1st rib. D. Mediastinal pleura: It forms the lateral boundary of the mediastinum and is divided into three parts a. Above the root of the lung: It extends from the sternum to vertebral column. b. At the root of the lung: The mediastinal pleura passes laterally in the form of a tube enclosing the structures of the root of lung. It continues with pulmonary pleura. c. Below the root of the lung: The mediastinal pleura forms a bilaminar fold known as pulmonary ligament which extends from

Thoracic Cavity and Pleurae

221

I. Oesophagus to corresponding lung below its hilum. At the hilum, the two layers are continuous with pulmonary pleura. IL Contents of pulmonary ligament: No important structures pass except i. Loose areolar tissue, ii. Lymphatics, and iii. Sometimes accessory bronchial artery.

2. Applied anatomy ► ►

► ► ► ►

►

Pleuritis: Inflammation of pleurae is known as pleurisy or pleuritis. It may be dry or wet pleurisy. Wet pleurisy is called pleural effusion. Thoracocentesis: It is the tapping of the fluid from the pleural cavity. It is performed in 8th intercostal space posterior to mid-axillary line. The needle is passed through the lower part of the intercostal space to avoid injury to the intercostal vessels and nerve. Pneumothorax: Presence of the air in the pleural cavity. Hemothorax: Presence of blood in the pleural cavity. Hydropneumothorax: Presence of both fluid and air in the pleural cavity. Empyema: Presence of pus in pleural cavity. Irritation of mediastinal and central part of diaphragmatic pleurae causes referred pain to the tip of shoulders. This is because of same segmental innervation.

X

.... ("i;j

i=0

CHAPTER

15 Lungs

l•)f+l•• Visceral relations of right lung 1. Chambers of heart

A. Right atrium,

B. Right auricle, and C. Right ventricle-small part. 2. Superior vena cava and its tributaries A. Right brachiocephalic vein, and B. Azygos vein. 3. Inferior vena cava, 4. Oesophagus, 5. Trachea, 6. Right vagus nerve, and 7. Right phrenic nerve. Please refer Fig. 15.1: Mediastinal surface of right lung (all blue structures) (SN-10)

l•)tiM Visceral relations of left lung 1. Chambers of heart A. Left auricle, B. Left ventricle-small part, and C. Right ventricle-adjoining part. 2. 3. 4. 5. 6.

Arch of aorta and its branch: Left subclavian artery. Descending thoracic aorta, Thoracic duct, Oesophagus, Trachea, 222

Lungs

223

7. Left vagus nerve and its branch-left recurrent laryngeal nerve. 8. Left phrenic nerve. Please refer Fig. 15.2: Mediastinal surface of left lung (all red structures) (SN-10)

(•)tJ:i Difference between right and left lungs Table 15.1: Difference between right and left lungs

I

Features • • • • • •

Right lung

Left lung

• 2

• 1

Fissures Lobes Anterior border Weight in gram Size Dimension

SN-1 O

• 3

• 2

• Straight

• Notched due to heart

• 700

• 600

• Larger • Shorter and broader

• Smaller • Larger and narrower

Mediastinal surfaces of the right and left lungs

X

.... ("i;j

1. Right side (venous) (Fig. 15.1)

A. Cardiac impressions and chambers a. Right atrium and auricle b . Right ventricle (small part) B. Veins a. Superior vena cava, b. Inferior vena cava, and c. Brachicephalic vein. d . Hilum is arched by azygos vein. C. Nerves

a. Vagus nerve, and b. Phrenic nerve. D. Trachea E. Oesophagus. 2. Left side (arterial) (Fig. 15.2)

A. Cardiac impressions and chambers a. Left ventricle b . Left auricle c. Left atrium d . Right ventricle

0

..c

r-

Exam-Oriented Anatomy

Superior Anterior+ Posterior Inferior

Right vagus----~ nerve

A\•'-'--c-_...._

Diagonal branch -

-Transverse branch

_,.___ Anterior interventricular branch

Septal ramus-s------- - - - -~

Fig. 17.16: The course and branches of left coronary artery

4. Distribution A. Anterior aspects of both right and left ventricles, B. Anterior two-thirds of the ventricular septum, C. Left branch of the AV bundle, D. Left surface of the left ventricle, and E. Posterior aspect of the left atrium.

5. Applied anatomy ►

Anterior interventricular branch of left coronary artery (left anterior descending artery-LADy artery) is the most commonly occluded vessel in the myocardial infarction. The circumflex branch of left coronary artery is a 3rd commonly occluded vessel in myocardial infarction. This artery is also called widow maker

Pericardium and Heart

►

►

►

► ►

263

artery. A widow maker heart attack is a type of heart attack that is caused by 100% blockage of the left anterior descending artery. It is also called "chronic total obstruction". The left coronary artery in addition to the usual distribution, supplies blood to the entire interventricular septum and atrioventricular node. In such cases, it is called left dominant coronary artery. Although the coronary arteries have numerous anastomoses at the arteriolar level, they are essentially functional end arteries', i.e. when a coronary artery is blocked the blood received by collateral channels is inadequate to meet the required demand in required time. The cardiac pain (due to angina pectoris or myocardial infarction) is usually referred to the left precordium and inner aspects of left arm and forearm. The heart is supplied by upper four thoracic (i.e. Tl-T4) spinal segments. The skin over precordium is supplied by T4, T3 and T2 spinal segments. The inner aspect of arm is innervated by T2 spinal segment. And the inner aspect of forearm and hand is innervated by Tl spinal segment. The cardiac pain is, therefore, referred to the precordium and inner aspects of X the arm and forearm because of the same segmental innervation. ....("i;j The cardiac pain is usually referred to the left side because cardiac lesions mostly o ..c occur in the left half of the heart, but if the lesion is in right half of the heart, the rpain will be referred on the right side. Hence, it is wrong notion that cardiac pain is always referred to the left side 'the left arm myth'. The coronary disease in old age is less fatal than in young age because anastomoses increase and collateral channels develop with the advancement of age. The slow gradual blocking coronary artery is less dangerous than sudden blockage because the arteries taking part in extra pericardiac anastomosis will dilate and provide blood supply to the heart.

l•)f+lfj Name the parts of heart tube. 1. Two endothelial heart tubes (right and left) appear and fuse to form one tube. This

tube has a venous end and an arterial end. 2. A series of dilatations appear on this tube. These are A. Bulbus cordis, a. Proximal one-third (which is dilated), b. Middle one-third called the conus, and c. Distal one-third called the truncus arteriosus. B. Ventricle, C. Atrioventricular canal: Narrow part connecting atrium and ventricle is the D. Atrium, E. Sinus venosus, and F. Right and left horns.

Exam-Oriented Anatomy Distal

+

Proximal Truncu s- - - - arteriosus

113rd

Conus----~ 113rd

Bulbous cordis

113rd

Ventricle---

-

Atrium

}""'

Body

X

venousus

....C1l 0

..c

Left horn

I-

Fig. 17.17: Parts of heart tube

-

Name the structures that fuse with each other at the level of atrioventricular canals so as to separate right and left side of the heart.

1. Septum primum, and

2. Two endocardial cushions.

•fit1f1t■ Venous drainage of the heart The veins draining the heart are divided in two groups. Superior Right + Left Inferior Coronary sinus

----Oblique vein of left atrium

5

+-Vein from left ventricle

-----Greater cardiac vein Middle cardiac vein ------

1. Great cardiac vein 2. Middle cardiac vein 3. Little cardiac vein 4. Vein of left atrium (oblique vein) 5. Vein of left ventricle

Fig. 17.18: Veins draining the heart

Pericardium and Heart

265

1. Veins draining into coronary sinus: This is a wide vessel that lies in the posterior

part of atrioventricular groove. It is covered by a thin layer of myocardium. It opens in the posterior wall of right atrium. It is left to the opening of inferior vena cava. The tributaries of the coronary sinus are compared to fingers of hand to memorize (Ref Fig. 17.18): A. Thumb represents great cardiac vein. B. Middle finger represents middle cardiac vein. C. Little finger represents small cardiac vein. D. Index finger indicates oblique vein of left atrium of Marshall. E. Ring finger represents posterior vein of left ventricle. The tributaries of the coronary sinus and their details are described in Table 17.5. Table 17.5: Veins draining into coronary sinus

Particulars • Great cardiac

I Situation • Anterior interventricular groove

I Draining area • Anterior part of interventricular septum • Anterior part of both ventricles

I Artery accompanying the vein

• Anterior interventricular artery (left coronary)

• Posterior interventricular groove

• Posterior part of inter- • Posterior interventricular septum ventricular (right • Posterior part of both coronary artery) ventricles

• Small cardiac

• Coronary sulcus

• Margins of right ventricle

-

-

-

2. Veins directly opening into the right atrium are described in Table 17.6 Table 17.6: Veins directly draining into right atrium

Particulars • Anterior cardiac vein. • Venae cordae minimi (Thebesian vein)

SN-27

I

Situation

I

• Atrioventricular groove

-

Draining area

I Termination

• Anterior surface of right ventricle

• Right atrium

• Endocardium

• Right atrium

Development of interatrial septum

1. Chronological age: It develops in the 4th week of intrauterine life (IUL).

2. Germ layer: Splanchnic layer of lateral plate mesoderm. 3. Site: From the roof of primitive atrial chamber.

("i;j

0

..c

• Middle cardiac

• Posterior part of • Oblique vein of the left atrium left atrium (vein of Marshal)

X

.... r-

Exam-Oriented Anatomy

IRight +

Roof of primitive----~ atrial chamber Sep tum

r

Left

I

ecundum Spurium

Sinoatrial orifice

L

Fig. 17.19: Development of interatrial septum

4. Sources X

....C1l 0

..c I-

A. Septum primum: A thin crescent

L

shaped membrane grows from the roof of

primitive common atrial chamber. It grows downward in the direction of septum intermedium (fused atrioventricular cushion). This septum is called septum primum. There is a gap between lower end of septum primum and septum intermedium called ostium primum. Before lower end of septum primum fuses with septum intermedium, upper part breaks open and the gap is formed which is called ostium secundum. B. Septum secundum: Another crescentic membrane arises on right side of septum primum and on left side of valve of septum spurium (false). There is a noval gap between septum primum and septum secundum. It is called foramen ovale. The blood coming from right atrium passes to left atrium through foramen ovale. C. At birth, the left atrium receives blood from lungs by four pulmonary veins. Due to increase in the volume of blood, the pressure is increased in left atrium. The septum secundum and septum primum approximates and interatrial septum is developed. 5. Anomalies: Atrial septal defect is common anomaly. A. Incidence: 0.07%

9:

male Cf' infant. B. Gender variation: 2 to 1. Female C. Types: It is of three types a. Cor triloculare biventricular: This is the most serious abnormality of atrial septal defect I. It is three-chambered heart with two ventricles. II. There is complete absence of the interatrial septum. III. It is always associated with serious defects elsewhere in the heart. b. Osteum primum defect is caused by I. Defective formation of atrioventricular (endocardial) cushion, or II. Failure of the septum primum to reach the atrioventricular cushion.

Pericardium and Heart

267

c. Osteum secundum defect: It is a most significant defect. It is caused by I. Failure of development of septum secundum, and IL Excessive resorption of septum primum. d. Patent foramen ovale is caused by failure of approximation of septum primum and septum secundum after birth. It is clinically not significant as it does not allow shunting of blood. SN-28

Development of interventricular septum

1. Chronological age: It develops in the 7th week of intrauterine life (IUL).

2. Germ layer: Splanchnic layer of lateral plate mesoderm. 3. Site: From the floor of the common ventricular chamber (bulboventricular cavity). 4. Sources: It has two parts: Muscular and membranous parts A. Muscular part forms the major part of the interventricular septum. It arises as a muscular ridge or fold, the interventricular septum from the primitive ventricular chamber. B. Membranous part: It is also called interventricular foramen. It exists between X the free age of interventricular septum and the fused endocardial cushion. It ~ permits communication between right and left ventricles up to the end of 7th _g week. It has two parts fa. Anterior membranous part develops from atrioventricular endocardial cushion. It is also called intermediate septum (septum between right atrium and left ventricle). The atrioventricular canal is formed between the primitive atrium and primitive ventricle. Initially the canal is round and changes to oval c:=). Two elevations develop on the anterior and posterior walls of this canal, which get fused and form septum intermedium. This communicates with right and left side of atrium to right and left side of ventricle.

Q

b. Posterior membranous part is formed by right and left bulbar septum. 5. Anomalies A. Ventricular septal defect (VSD): This is the most common congenital anomaly of the heart. It is because of failure of fusion of endocardial cushion or the atrioventricular canal. B. Pentalogy of Fallot a. Pulmonary stenosis b. Right ventricular hypertrophy c. Overriding of the aorta d. Ventricular septal defect e. Atrial septal defect C. Fallofs tetralogy (Fig. 17.20) (tetralogy means four defects): It is most common

congenital cyanotic heart disease. The main defect is an unequal division of the conus leading to narrow pulmonary and wide ascending aorta. It is characterized by

;.

....,.

_

~

Overriding of aorta

Pulmonary trunk

Fig. 17.20: Fallot's tetralogy

C. Diagrammatic representation of Fallot's tetralogy

0.

'


co

co·

Ventricular septa! defect

Q

m

s3

::,

B. Normal flow of blood through pulmonary artery and ascending aorta

I\)

00

0)

Pulmonary stenosis Right ventricular hypertrophy Overriding of aorta

Right ventricular----hypertrophy A. Manifestation of Fallot's tetralogy

Ventricular septal defect

Stenosis of~ pulmonary trunk

p:

Right+Left Inferior

Superior

Thorax

Pericardium and Heart

269

I.... PRO-V I Pulmonary stenosis, Right ventricular hypertrophy, Overriding of the aorta, and Ventricular septal defect. The clinical manifestations are breathlessness on exertion. The child suddenly ceases his activity and lies in the knee chest position "squatting posture", by doing so he gets relief probably because squatting reduces the venous return by compressing the abdominal veins and increases the systemic vascular resistance by kinking the femoral and popliteal arteries. Both these mechanisms tend to decrease the right to left shunt through ventricular septal defect and improve the pulmonary circulation. SN-29

Development of left atrium

1. Chronological age: It develops in the 5th to 7th week of intrauterine life (IUL).

2. Germ layer: Mesoderm. 3. Site: Primitive atrial chamber.

X

.... ("i;j

0

..c

r-

Pulmonary trunk • xxx" " - Spiral septum ---Fused atrioventricular cushions

J

Atrioventricular Right orifice Left

Fused atrioventricular cushions

Fig. 17.21 : Development of left atrium

4. Sources A. The posterior smooth part (between the openings of the pulmonary veins) develops from the incorporation of the endocardial cushions of the four pulmonary veins.

B. The anterior part (which is somewhat trabeculated including the left auricle) develops from the left half of the primitive atrium. C. The most ventral part develops from the left half of the atrioventricular canal. SN-30

Development of portal vein

1. Chronological age: It develops in the 5th to 7th week of intrauterine life (IUL).

2. Germ layer: Mesoderm. 3. Site: Around the duodenum.

Exam-Oriented Anatomy

4. Sources Table 17.7: Sources of different parts of the portal vein

I Develops from

Part • Infraduodenal part • Retroduodenal art • Supraduodenal part • Right branch • Left branch

• Parts of left vitelline vein from joining of splenic vein to dorsal intervitelline anastomosis. • Dorsal anastomoses between ri ht and left vitelline veins. • Right vitelline vein between dorsal anastomosis and cephalic ventral anastomosis. • Cephalic parts of right vitelline vein cranial to cephalic intervitelline anastomosis. • Cephalic ventral anastomosis and left vitelline cranial to cephalic ventral intervitelline anastomosis.

l•)tiii Tributaries of inferior vena cava Tributaries: The tributaries of vena cava are not identical with the branches of the abdominal aorta. Especially, there are no corresponding veins to the three ventral branches to the gut. Following are the tributaries of the inferior vena cava. X ~ 1. Pair of common iliac veins. _g 2. Lumbar veins. IA. 3rd and 4th pair of lumbar veins drain directly into the inferior vena cava. B. 1st and 2nd drain into ascending lumbar vein. C. A pair of renal veins, D. A pair of phrenic veins, E. Right gonadal vein, and F. Right suprarenal vein and hepatic veins. Superior Right + Left Inferior Inferior phrenic vein Suprarenal vein

·F--t,~

,,...---------

Hepatic veins

r-- Inferior phrenic vein

----+

+--

Renal vein

Suprarenal vein Renal vein Gonadal vein

Gonadal vein - --

- - - Inferior vena cava

Common iliac vein

~ - - Median sacral vein

Fig. 17.22: Inferior vena cava and tributaries

Pericardium and Heart

SN-31

271

Development of inferior vena cava

1. Chronological age: It develops in the 5th to 7th weeks of intrauterine life (IUL).

2. Germ layer: Splanchnic layer of lateral plate mesoderm. Cranial Right + Left Caudal

Transverse communication-between supra- and subcardinal veins

-

-

-

~ /'+'c!!!---

Mesonephros

1-(-,."--',~~.:..>----l...::.:./ · } Stratified squamous non>v--v-v-..rv""'°"~'~'"'•A

keratinised epithelium

~..................--L.._._..L-L_._L....L..J.- Basement

membrane

Fig. 19.6: Lining epithelium of oesophagus

(•)f+IJ• What is the peculiarity of the musculature of oesophagus? 1. It is thick and differs in upper, middle and lower parts of oesophagus.

2. Upper one-third is formed by skeletal muscle.

r-

Exam-Oriented Anatomy

3. Middle one-third is formed by skeletal and smooth muscle. 4. Lower one-third is formed by smooth muscle. Where do we find glands in oesophagus? What is their clinical importmtl!I _ once?

The wall of the oesophagus contains two types of glands that secrete mucus but are located in different parts of the organ. l. Oesophageal cardiac glands: They are present in the lamina propria of the proximal

and distal parts of the oesophagus. They resemble the mucous glands located in the cardiac region of the stomach. 2. Submucosa contains proper oesophageal glands A. They are compound tubuloalveolar mucous glands.

B. They are scattered along the entire length of the oesophagus. C. They produce mucus that lubricates the lumen of the oesophagus. X

....

C1l

0

..c I-

3. Functions A. They protect the mucosa .

B. They facilitate smooth passage of food material (bolus) through the oesophagus to the stomach. ,

Describe oesophagus under following heads 1. Gross anatomy, 2. Histology.and 3. Applied anatomy.

1. Gross anatomy

A. Introduction: It is the longest muscular tube of gastrointestinal tract extending

from pharynx to stomach. B. Extent: It extends from lower border of cricoid cartilage (6th cervical vertebra) to cardiac orifice of stomach (10th thoracic vertebra). C. Oesophagus has physiological sphincter at the lower end of oesophagus.NEEr Constrictions: It shows four constrictions at the following levels

Where it is crossed by the Aortic arch. Where it is crossed by the left ]lronchus. At its !;ommencement (caused by .Cricopharyngeus sphincter). Where it pierces the Diaphragm.

1. . . . .

ABCD I.

Trachea, Oesophagus and Thoracic Duct Incisor teeth

289

-i.----------.- - -,~:~_::_::_::~:::=-=t- -.- - ---vi

V)

Q)

Q)

-5

-5

+-------;----+------,.- Pharynx

-~

.~ co

(J)

~

14 mm . ..,._-

-----,V)

Q)

-

+- Cricopharyngeus V)

Q)

.c

.c (.)

C

-~

(.)

I.CJ

19 mm

0 0

+ 22mm

~

+ Oesophagus

17 mm

X

.... ("i;j

0

..c

r-

Fig. 19.7: Constrictions and dilation of oesophagus in mm Table 19.2: Details of oesophagus regarding diameter and distance from incisor teeth

Sr. no. I Verteb,al I Featu,es level

Diameter inmm

I

I

Distance from incisor teeth (in inches)

• 6

I Cause fo, constrictions

1

• C6

• Constriction

• 14

2

• Tl

• Distension

• 19

3

• T4

• Constriction

• 16

• 9

• Crossing of arch of aorta

4

• T6

• Distension

• 22

• 11

• Crossing of left bronchus

5

• TlO

• Constriction

• 17

• 15

• Oesophageal opening in diaphragm

• Cricopharyngeus junction -

290

I

Exam-Oriented Anatomy Inferior thyroid artery

- - - - - Thoracic aorta

Oesophagus------.,

Oesophageal branch of

1. Inferior thyroid artery 2. Thoracic aorta 3. Left gastric artery

X

Left gastric artery

....

C1l

0

..c I-

Coeliac trunk

Fig. 19.8: Arterial supply of oesophagus

I

Right+ Left

I

-------Oesophagus Cervical part

i

j Thoracic part

Oesophageal vein tributary of 1. Right brachiocephalic vein 2. Azygos vein 3. Left gastric vein

l l

Abdominal part Left gastric vein

Fig. 19.9: Venous drainage of oesophagus

r

Trachea, Oesophagus and Thoracic Duct

291

Superior Right + Left Inferior

Left gastric lymph nodes Coeliac lymph nodes

O

Fig. 19.10: Lymphatic drainage of oesophagus X

.... ("i;j

Table 19.3: Blood supply and lymphatic drainage of oesophagus

Particulars

Upper (cervical)

Middle (thoracic)

Lower (abdominal)

Blood supply

• Oesophageal branches of inferior thyroid artery (subclavian artery)

• Oesophageal branches of thoracic aorta • Oesophageal branches of bronchial arteries

• Oesophageal branches of left gastric artery

• Venous drainage

• Oesophageal veins drain into inferior thyroid veinNEET > left brachiocephalic vein which drains into superior vena cava

• Oesophageal veins • Oesophageal drain into azygos vein drains vein which drains into left gastric into superior vena veins which cava drains into portal vein

• Lymphatic drainage

• Deep cervical lymph nodes

• Tracheobronchial lymph nodes and posterior mediastinal nodes

• Arterial supply

Lymphatics of oesophagus follows arteries

• Left gastric nodes and coeliac lymph nodes

D. I Nerve supply! a. Sympathetic fibres: These arise from TS - T9 segments of the spinal cord and form the oesophageal plexus. b. Parasympathetic fibres: These are derived from vagi and recurrent laryngeal nerves. The nerve cells in the myenteric and submucous plexuses act as postganglionic neurons for parasympathetic fibres only.

0

..c

r-

Exam-Oriented Anatomy

The congenital absence of these nerve cells produces disturbance in peristalsis and the condition is known as cardiospasm or achalasia (a-not; chalasisrelaxation). 2.

X

....C1l 0

..c I-

U@§imd:It is formed by four layers from inside out. A. Mucosa: It is thick and is in the collapsed state thrown into longitudinal folds. It consists of a. Surface epithelium of stratified squamous non-keratinized. It is replaced by columnar epithelium at the gastro-oesophageal junction. b. Lamina propria. c. Thick muscularis mucosa which shows an internal circular layer and an external longitudinal layer. A nerve plexus may be found among the muscle fibres. B. Submucosa: It contains all connective tissues. It contains mucous glands which are sparse and are found in the upper and lower ends. The secretion lubricates the oesophagus. It contains a. Submucous glands, and b. Plexus of I. Arteries, IL Veins, III. Lymphatics and IV. Nerves.NEET C. Muscularis extema: It consists of inner circular and outer longitudinal, which are of skeletal muscle in the upper part and smooth muscle in the lower part. It is the longest smooth muscle cells of the body. D. Serosa is lined by thick fibrous coat.

3. Applied anatomy ► Oesophageal varices: The lower end of oesophagus is one of the main sites of portocaval anastomosis. Here the tributaries of left gastric vein anastomose profusely with the tributaries of azygos and hemiazygos veins.

- - - - - -- Oesophagus Azygos vein

Oesophageal vein

Fig. 19.11: Anastomosis between superior vena cava and portal vein through oesophageal venous

plexus

Trachea, Oesophagus and Thoracic Duct ►

►

►

293

In portal hypertension, there is shunting of the blood from portal to caval system. There is dilatation and tortuosity of these collateral channels which is called oesophageal varices. Rupture of these veins results into haematemesis (i.e. vomiting of frank red-coloured blood). This differentiates haematemesis arising from perforation of gastric ulcers which is black-red in colour. Dysphagia: Difficulty in swallowing which is seen on obstruction called dysphagia while painful swallowing odynophagia. This can be diagnosed by barium swallow. Achalasia cardia: It is due to neuromuscular in-coordination of muscles of the lower end of oesophagus. This results into loss of peristalsis and there is a failure of relaxation of the lower end of oesophagus. Consequently, the food accumulates in the oesophagus causing regurgitation. The regurgitant does not include gastric contents and is not sour tasting. The achalasia is the most common oesophageal motility disorder, with an incidence of 6 per 100,000 individuals. Describe thoracic duct under following heads 1. Gross anatomy, X

2. Tributaries,

....

3. Histology,

..c

4. Development, and 5. Applied anatomy.

1. Gross anatomy

A. Introduction: It is a lymphatic channel present in the thoracic region. It drains the lymph from lower half and left upper half of the body. B. Appearance: Beaded. C. Measurement: Length x width (cm) 45 x 0.5 D. Extent: Lower border of T12 vertebra to 7th cervical vertebra. E. Commencement: It commences from the cranial end of cisterna chyli. F. Termination: It terminates in the left brachiocephalic vein at the junction of left subclavian and left internal jugular veins. G. Course and relations (Fig. 19.12) a. It passes through the aortic opening of diaphragm which is present at 12th thoracic vertebra. b. Here it accompanies on the left side by descending thoracic aorta and on the right side by azygos vein. c. It lies posterior to oesophagus up to 5th thoracic vertebra. d . It ascends upward and at level of 5th thoracic vertebrae, it takes left turn and enters the superior mediastinum. e. At the level of 7th cervical vertebra, it arches laterally, which is 3 to 4 cm above the left clavicle.

("i;j

0

r-

Exam-Oriented Anatomy

I

Right +

Left ! Internal jugular vein

Oesophagus------:

,.__ Subclavian vein

---o

~

Brachiocephalic vein \ - - - - - VagosceNe

Recurrent laryngeal nerve

~

O ""1

Four parallel structures a "unit of 4"

Trachea Oesophagus Recurrent laryngeal nerve (Left) Thoracic duct

X

....C1l 0

..c I-

- - - - - - Descending thoracic aorta

Stomach

--