Thieme Dissector Volume 1 E-Book

Vishram Singh

• Herausgeber: Thieme Medical Publishers
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2024

Beschreibung

<p>Thieme Dissector, Second Edition is a richly illustrated and detailed three-volume manual for guiding students and teachers in the dissection lab. It is enriched with intricate illustrations of the human anatomy created from the clinician’s perspective. These illustrations and the carefully researched and structured text elucidate the layer-by-layer dissection of each region of the human body in a stepwise manner.</p><p></p><p>The volumes have been created by renowned experts in the field: Dr. Vishram Singh, Dr. G. P. Pal, Dr. S. D. Gangane, and Dr. Sanjoy Sanyal. The text of the volumes flows lucidly through well-defined sections in each chapter. These sections have also been made visually distinct to aid access. The authors have aimed to make the reading of these volumes educative, interesting, and visually engaging.</p><p> </p><p>Salient Features of the Second Edition</p><p> </p><ul><li>Updated videos: Provides access to more than 100 new videos on Thieme MedOne to facilitate learning, understanding, and comprehension. These videos enhance the scope of understanding the topic under discussion.</li><li>Dissection screenshots: Most relevant and duly labelled screenshots from the cadaveric dissection videos are presented at suitable places within the text to provide better insight into the steps of dissection.</li><li>Radiographs: Includes newly added radiographs to help broaden the gamut of interpretation of the anatomy.</li><li>New section: A new section on “Vertebral Column” has been added to Volume I for extensive coverage of the back region.</li></ul><p>This book includes complimentary access to a digital copy on <a href="https://medone.thieme.com./">https://medone.thieme.com.</a></p><p><strong>Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product.</strong></p>

Leseprobe

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Thieme Dissector

Second Edition

Volume I

Upper Limb and Thorax

Thieme Dissector

Second Edition

Volume I

Upper Limb and Thorax

Vishram Singh, MBBS, MS, PhD (hc), MICPS, FASI, FIMSA

Adjunct Professor

Department of Anatomy

KMC, Manipal Academy of Higher Education

Mangalore, Karnataka, India;

Editor-in-Chief

Journal of the Anatomical Society of India;

Member, Federative International Committee for Scientific Publications (FICSP)

International Federation of Association on Anatomists (IFAA)

Geneva, Switzerland

G. P. Pal, MBBS, MS, DSc, FASI, FAMS, FNASc, FASc, Bhatnagar Laureate

Director Professor

Department of Anatomy

Index Medical College;

Emeritus Professor

MGM Medical College

Indore, Madhya Pradesh, India

S. D. Gangane, MBBS, MS, FAIMS

Professor and Head

Department of Anatomy

Terna Medical College

Navi Mumbai, Maharashtra, India

Sanjoy Sanyal MBBS, MS, MSc, ADPHA

Provost and Dean

Professor and Department Chair Anatomical Sciences

Richmond Gabriel University College of Medicine

St. Vincent and the Grenadines

Canada

Based on the work of

Michael Schuenke

Erik Schulte

Udo Schumacher

Illustrations by

Markus Voll

Karl Wesker

ThiemeDelhi • Stuttgart • New York • Rio de Janeiro

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Senior Development Editor: Dr. Gurvinder Kaur

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Cover design: Thieme Publishing Group

Cover image source: Voll M and Wesker K

Illustrations by Voll M and Wesker K. From: Schuenke M, Schulte E, Schumacher U, THIEME Atlas of Anatomy.

Page make-up by RECTO Graphics, India

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5 4 3 2 1

ISBN: 978-93-92819-09-4

Also available as an e-book:

eISBN (PDF): 978-93-92819-14-8

eISBN (ePub): 978-93-92819-16-2

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Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers’ leaflets accompanying each drug and to check, if necessary, in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released in the market. Every dosage schedule or every form of application used is entirely at the user’s own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page.

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To my students, past and present.

Vishram Singh

To my grandson, Yatharth.

G. P. Pal

To my family and colleagues, for their support; my patients and students, for teaching me to learn from them; the willed body-donors, for their silent altruism to medical science.

Sanjoy Sanyal

Contents

Video Contents

Note from the Authors

About the Authors

Contributor to Volume I

Introduction to Dissection

1.Osteology of the Upper Limb

2.Pectoral Region and Axilla

3.Dissection of the Back

4.Scapular Region and Shoulder

5.Anterior Compartment of the Arm and Cubital Fossa

6.Posterior Compartment of the Arm

7.Flexor Compartment of the Forearm and Palm

8.Extensor Compartment of the Forearm and Dorsum of the Hand

9.Nerves of the Upper Limb

10.Joints of the Upper Limb

11.Introduction to Thorax

12.Skeleton of the Thorax

13.Thoracic Wall

14.Thoracic Cavity

15.Joints of the Thorax

Appendix

Index

Video Contents

Video 2.1

Structure of breast

Video 2.2

Pectoral region

Video 2.3

Neurovascular structures from axilla to cubital fossa

Video 2.4

Course of axillary and brachial arteries

Video 4.1

Deltoid muscle and axillary nerve

Video 5.1

Flexor/anterior compartment of arm

Video 6.1

Ulnar and radial nerves

Video 7.1

Flexor compartment of forearm and neurovascular structures

Video 7.2

Neurovascular structures of the palm

Video 8.1

Extensors of forearm and dorsum of hand

Video 9.1

Musculocutaneous, axillary, and radial nerves

Video 13.1

Structures of the anterior thoracic wall

Video 14.1

Relations of mediastinal surface of lung

Video 14.2

Mediastinum and great blood vessels

Video 14.3

Azygos and hemiazygos veins and thoracic duct

Video 14.4

Pericardial sinuses

Video 14.5

External features of heart

Video 14.6

Blood vessels of heart

Video 14.7

Internal features of right atrium of heart

Video 14.8

Internal features of right ventricle

Video 14.9

Aortic arch and descending thoracic aorta

Note from the Authors

There was a long-felt need of a good dissection manual for first-year undergraduate medical students undertaking the anatomy course. Anatomy is the foundation of all medical subjects, and hence, its thorough knowledge is essential for all students aspiring to become good doctors, especially in surgical fields.

The best modus operandi to learn anatomy is through dissection. Recently, due to information explosion in the medical field, the health sciences curricula have markedly reduced the time allocation for studying and teaching anatomy; yet it is realized by all that the gross structure of the human body, including its three-dimensional conceptualization, must be understood thoroughly before proceeding further to learn medicine.

Therefore, we have made a sincere effort to meet all the needs of the students in creating this three-volume set of dissection manuals. They not only delineate instructions for students to perform perfect dissection but also provide gross anatomy descriptions, supplemented by clinical correlations of gross structures studied during dissection. The textual descriptions are complemented by numerous colored illustrations that will help students recognize significant structures with more precision. To further enhance understanding, the content of the volumes is organized in sections like (a) Learning Objectives, (b) Surface Landmarks, (c) Dissection and Identification, (d) Description of Gross Anatomy, and (e) Clinical Notes. Laced with all these features, we hope that these volumes will be useful not only for medical and dental students but also for teachers of anatomy. The value of these volumes is further enhanced by providing videos at relevant places.

As educators of anatomy, we have tried our best to make these manuals easy for learning. We highly appreciate the contribution of Prof. Poonam Kharb and Mr. D. Krishna Chaitanya in Volume II and Prof. Shabana M. Borate in Volume I. For further improvements, we would sincerely welcome comments and suggestions from all students and teachers.

The second edition of this dissection manual is thoroughly updated with new line diagrams, X-ray pictures, and CT and MRI scans.

All dissection steps are supplemented by dissection videos in all the three volumes for easy understanding of gross and clinical anatomy by the students.

Vishram Singh, MBBS, MS, PhD (hc), MICPS, FASI, FIMSA

The medical curriculum in India requires basic anatomy, along with some other basic subjects, to be taught to students in the first year of the course. This often leads to an information overload for them. For some students, the situation is made even more difficult due to linguistic limitations and late admissions. As a result, there has long been a pressing need for comprehensive teaching resources that create thorough understanding of these courses in a short time span. Specifically for anatomy, one cannot stress enough on the value of a complete and detailed dissection manual that explains basic concepts in a simple and lucid manner, without duplication of facts or unnecessary complexities.

In Volume III, every care has been taken to describe all steps involved in the dissection of the head, neck, and brain in a stepwise manner that is easy to understand for the beginners. Several high-quality illustrations have been used to explain each step. They help show the dissections with a great amount of detailing and clarity. To make the discourse interesting, relevant clinical conditions have also been presented under separate sections called “Clinical Notes.”

Producing a book with hundreds of illustrations is a joint effort by the author and the publisher in a true sense.

I strongly believe that this book will be an invaluable learning resource for students and teachers of anatomy in medical and dental courses.

G. P. Pal, MBBS, MS, DSc, FASI, FAMS, FNASc, FASc, Bhatnagar Laureate

Cadaveric dissection is an integral part of teaching anatomy in medical schools. It offers an unmatched firsthand experience of exploring the structure of organs and their relationship with each other. Thieme Dissector provides a complete account of dissection of human body through a set of three volumes.

The first volume deals with the upper limb and thorax. The introduction of this volume gives general information about preservation of cadaver, instruments required for dissection, and anatomical terms, followed by a discussion on basic tissues of the body. This is followed by 10 chapters on upper limb and 5 chapters on thorax. Each chapter begins with “Learning Objectives,” followed by an introduction to the topic, dissection steps with description of the relevant structures, and clinical notes.

To facilitate understanding of the subject, photographs of actual dissected parts and real dissection videos have been provided. Access to these videos will help and enrich students’ learning process.

My heartfelt gratitude to Dr. Shabana M. Borate, Associate Professor, Department of Anatomy, at Grant Government Medical College and Sir J. J. Group of Hospitals, Mumbai, Maharashtra, India, Dr. Sachin Yadav, Assistant Professor at Grant Government Medical College and Sir J. J. Group of Hospitals, Mumbai, Maharashtra, India, and Dr. Shilpa Domkundwar, Professor and Head, Department of Radiodiagnosis, Grant Government Medical College and Sir J. J. Group of Hospitals, Mumbai, Maharashtra, India, for their untiring efforts in preparation of this volume. I am grateful to the entire team of Thieme Publishers for their constant support, and special thanks to Dr. Vishram Singh sir, who has been the guiding force for all of us in preparation of the Thieme Dissector.

S. D. Gangane, MBBS, MS, FAIMS

Thieme has taken a positive step by introducing this book for imparting anatomy education to medical students worldwide. The process of depicting videos and pictures of actual cadaver dissections in a textbook is indeed a monumental task. It starts with planning of the region to be dissected. This is followed by meticulous dissection of the region itself, which can take hours if not days. Then comes the process of accurate live narration of the dissection of the region on camera, while the video recording is in progress. The back-breaking task of editing and captioning the video frames and clips follows next, because many anatomical and medical terms used in the narration may otherwise be incomprehensible to the student. Since clinical students like content related to radiology, some videos have radiological images embedded within the frames. The relevant still shots from the dissections are then edited and labeled. Finally, of course, comes the task of publishing the finished product.

There are many digital anatomy tools available to the medical academia, ranging in size and versatility from usage in classrooms and digital labs to those used in individual laptops and tablets. Some have virtual reality–like, immersive three-dimensional, or augmented reality applications. They vary in accuracy, comprehensiveness, and versatility. They are good study tools, which are interactive and interesting to use in teaching and learning anatomy. They show body parts and spatial relationships. They are available offline, accessible anytime, anywhere, and can even show rare pathology. They present consolidated anatomy information to suit users’ learning styles. They do not have the legal, ethical, religious, social, regional, and logistical constraints of human cadaver procurement. These factors are weaning away institutions from the hoary art of cadaver dissection.

However, cadaver dissection is still the gold standard for learning human anatomy and surgery. It is the benchmark for measuring the success of newer learning technologies. Cadavers are medical students’ first “patients.” Digital resources are to be considered as supplements to the armamentarium of learning methods in human anatomy. Digital technologies lack haptic qualities of human tissue, which are essential for a surgeon. Therefore, they can never completely replace cadaver dissection for anatomy students and surgical residents under training. Nobody would want to be treated by surgeons who acquired their entire quantum of expertise in operating on the human body through virtual reality alone, just like nobody would want to be flown by an airline pilot whose only flying experience was in the digital flight simulator.

The author is truly gratified knowing that students have learned the subject of anatomy and mastered the intricacies of the human body by watching Thieme Dissector videos and illustrations.

Sanjoy Sanyal, MBBS, MS, MSc, ADPHA

About the Authors

Vishram Singh

(Editor-in-Chief and Author, Volume II, Abdomen and Lower Limb)

Vishram Singh, MBBS, MS, PhD (hc), MICPS, FASI, FIMSA, is currently the Adjunct Professor, Department of Anatomy, KMC, Manipal Academy of Higher Education, Mangalore, Karnataka, India; Editor-in-Chief, Journal of the Anatomical Society of India; and Member, Federative International Committee for Scientific Publications (FICSP), International Federation of Association on Anatomists (IFAA), Geneva, Switzerland.

A renowned anatomist, Prof. Singh has taught undergraduate and postgraduate students at several colleges and institutes, such as GSVM Medical College, Kanpur; King George Medical College, Lucknow; All India Institute of Medical Sciences, New Delhi; and Al Arab Medical University, Benghazi, Libya. He has more than 50 years of experience in teaching, research, and clinical practice. He has various bestselling titles to his credit, such as Textbook of Clinical Neuroanatomy, Textbook of Anatomy—three volumes, and Textbook of Clinical Embryology. He has published more than 20 books and more than 100 research articles in reputed national and international journals.

Prof. Singh has received various recognitions and awards for his contributions in the field of gross anatomy, neuroanatomy, and embryology.

He has been elected Vice President of the Anatomical Society of India many times. He is currently Editor-in-Chief, Journal of Anatomical Society of India (JASI).

G. P. Pal

(Author, Volume III, Head, Neck, and Brain)

G. P. Pal, MBBS, MS, DSc, FASI, FAMS, FNASc, FASc, Bhatnagar Laureate, is currently the Director Professor of Anatomy at the Index Medical College; Emeritus Professor at MGM Medical College, Indore, Madhya Pradesh, India. Dr. Pal is an eminent teacher with almost five decades of teaching experience in various medical colleges of India and the United States. He has to his credit numerous publications in journals of international repute. He has received several national awards and honors for his research works, which includes Shakuntala Amir Chand Prize of Indian Council of Medical Research (ICMR), Shanti Swarup Bhatnagar Prize of Council of Scientific and Industrial Research (CSIR), and several gold medals, oration awards, and Lifetime Achievement Award by the Anatomical Society of India. He has been elected Fellow at various leading academies of sciences in India—Anatomical Society of India; National Academy of Medical Sciences (New Delhi), National Academy of Sciences (Allahabad), and Indian Academy of Sciences (Bengaluru). His research work is cited in more than 100 standard medical textbooks throughout the world. Recently, his name featured in the list of top 2% scientists of the world. As per a survey conducted by the Stanford University, USA, in 2020, he is ranked as no. 1 Anatomy Scientist in India and 102 in the world. Dr. Pal has authored many well-received books such as Textbook of Histology, Illustrated Textbook of Neuroanatomy, Medical Genetics, Genetics in Dentistry, General Anatomy, Basics of Medical Genetics, Human Osteology, Genetics for Dental Student, Neuroanatomy for Medical Students, and Thieme Dissector. He has edited 16th South Asian edition of Grant’s Atlas of Anatomy (in press). He has also coauthored Prof. Inderbir Singh’s Human Embryology from the 7th to 9th editions. For more information about the author and his works, Google “Indian Anatomists - Wikipedia” or “Gaya Prasad Pal - Wikipedia.”

S. D. Gangane

(Author, Volume I, Upper Limb and Thorax)

S. D. Gangane, MBBS, MS, FAIMS, is currently serving as Professor and Head, Department of Anatomy at Terna Medical College, Navi Mumbai, Maharashtra, India. He has been Professor and Head, Department of Anatomy and Genetic Division at Grant Medical College, Mumbai and Sir J. J. Group of Hospitals, Mumbai. This is a unique Anatomy Department offering services to patients having genetic disorders. Prof. Gangane has authored a bestselling book titled Human Genetics which has been widely accepted by faculty and both undergraduate and postgraduate students.

Prof. Gangane has over four decades of teaching experience and has been guiding students for MD Anatomy, and MSc and PhD in Applied Biology courses at the Mumbai University. He has also been a guide for the MD Anatomy and PhD Genetics courses at Maharashtra University of Health Sciences (the State Health University). He has published several articles in national and international journals and is also a coauthor of the recently published Textbook of Pathology and Genetics for Nurses. In addition, he has been on the national advisory board and the executive editorial board for a few journals, including Indian Journal of Anatomy and National Journal of Medical Sciences.

Prof. Gangane has also worked as an Officer of Special Duty (OSD) for the Government of Maharashtra under the Directorate of Medical Education and Research. He is a member of the advisory panel for the South Asian region of the international publishing house, Lippincott Williams and Wilkins. He is the founder Trustee of “Sandnya Sanwardhan Sanstha”, an organization that takes care of mentally challenged children by imparting vocational training and enabling them to lead better lives.

Sanjoy Sanyal

(Contributor of Videos, Volumes I, II, and III)

Sanjoy Sanyal, MBBS, MS, MSc, ADPHA, is the Provost and Dean of Richmond Gabriel University College of Medicine, St. Vincent and the Grenadines, Canada. He is also the Professor and Department Chair of Anatomical Sciences in the same university. With medical degrees from India and the United Kingdom, Dr. Sanyal has 39 years of clinical, surgical, and teaching experience as a surgeon, surgical anatomist, neuroscientist, and medical informatician.

A prolific medical and educational researcher, he has published 25 original research papers in peer-reviewed journals and presented 15 papers in many international conferences in 11 countries. He is the recipient of five Outstanding Professor Awards from several different universities and medical schools.

He is a surgical skills instructor to American Medical Students’ Association (AMSA). He is a life-member of Indian Medical Association (IMA), and annual member of American Association for Anatomy (AAA) and American Association of Clinical Anatomists (AACA). He is a provisional patent holder (January 2014) of a computerized medical program from the United States Patent and Trademark Office (USPTO). He is peer reviewer of several medical journals.

Dr. Sanjoy Sanyal is honorary faculty of the Multimedia Educational Resource for Learning and Online Teaching (MERLOT), a program of the California State University (CSU), Long Beach, partnering with educational institutions, professional societies, and industry. He is Gold-level MERLOT contributor, having authored more than 350 learning materials. He is a member of Virtual Speaker’s Bureau (VSB) of MERLOT. He is also the recipient of Innovative Use of MERLOT award.

With an underpinning philosophy of lifelong learning, his motto is to make each succeeding generation better than the previous.

Contributor to Volume I

Shabana M. Borate, MBBS, MS, PhD (Medical Genetics)

Associate Professor

Department of Anatomy

Grant Government Medical College and

Sir J. J. Group of Hospitals

Mumbai, Maharashtra, India

Introduction to Dissection

Anatomy is one of the basic subjects in medical education. It deals with the structure of human body. A sound knowledge of this subject provides better understanding of the clinical subjects. The subject of anatomy is best studied by dissection. It will be appropriate to say that dissection forms an integral part of teaching or learning anatomy. It gives you an opportunity to explore, observe, and learn about structures/organs. The experience that you gain in the dissection room is unmatched. It cannot be compared to learning through books, illustrations, CDs, and DVDs that are available to learn the subject. Dissecting a cadaver improves your skill of handling the tissues and instruments that you will be trying later when you start practicing on living subjects. It gives you an understanding about the relationship of various structures to each other and helps you know what is normal and what is anomalous. It offers an anatomical basis of tests that you may do, various signs and symptoms that you encounter in a patient, variations that you may see in some subjects, and overall better understanding of many disease processes. It is well said that the cadaver is the best teacher of anatomy. Once it is accepted, it is our duty to treat the cadaver with the same respect and dignity which is offered to a living patient.

Preservation of the Cadavers

It is done by embalming the cadaver with the embalming fluid which contains a strong fixative. Subsequently, the cadaver is submersed in the preservative fluid. When the cadaver is partly dissected, proper care should be taken by wrapping it so that it is kept moist, or else the cadaver will desiccate and once the part is dry it cannot be restored. Therefore, expose only the part which is to be dissected. Ideally, all the parts of the body should be periodically inspected and moistened during the dissecting session.

Anatomical Terms

It is essential to get familiar with many anatomical terms which are repeatedly used to describe structures, organs, parts, etc. Some of them are given in the following paragraphs.

Anatomical Position

It is the position of the body with the person standing erect, feet approximated (together), toes pointing forward, arms hanging by the side of the body, palms facing forward, and the eyes looking at horizon (Fig. 1).

All the descriptions in anatomy are provided assuming the body is in anatomical position, though the cadaver is lying horizontally on the dissection table. Its relationship with the neighboring structures is essential when you study the structure; remember that the description applies assuming the structure is in anatomical position. The frequently used terms can be put into two groups: the terms of positions and the terms of movements.

Fig. 1 Anatomical position.

Terms of Positions (Fig. 2)

1.Anterior: It means nearer to the front of the body.

2.Posterior: It means nearer to the back.

3.Ventral and dorsal are used in the case of trunk instead of anterior and posterior, respectively.

4.In the hand, palmar means anterior and dorsum means posterior. In the foot, the terms used are dorsum for the upper side and plantar for the sole of the foot.

5.Median: It means in the middle.

6.Medial: It means nearer the median plane.

7.Median plane: It is an imaginary plane bisecting the body into nearly two equal halves.

8.Lateral: It means away from the median plane; for example, there are two forearm bones, the radius is on the lateral side and the ulna is on the medial side. In the bones of the leg, the tibia is on the medial side and the fibula is on the lateral side.

9.Superficial: It means nearer to the skin of surface.

10.Deep/Profundus: It means deeper (as compared to superficial) from the surface.

11.Proximal (nearer to): It indicates relative position of the structure.

12.Distal (further from): For example, elbow is distal to the shoulder but proximal to the wrist.

13.Superior/Cephalic: The term refers to the position of the part which is nearer to the head.

14.Inferior/Caudal: It means nearer to the feet.

Fig. 2 A diagram illustrating the use of anatomical terms. (From: Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy. General Anatomy and Musculoskeletal System. Illustrations by Voll M and Wesker K. © Thieme 2020.)

Anatomical Planes

There are four imaginary planes (Fig. 3) that pass through the body in anatomical position:

1.Median/Sagittal plane: A vertical plane which passes through the center of the body and divides it into two equal halves.

2.Paramedian/Parasagittal plane: Any vertical plane which is parallel to the median plane.

3.Coronal plane: Any vertical plane perpendicular to the median plane.

4.Transverse/Horizontal plane: Any plane at right angle to coronal and sagittal planes.

Fig. 3 Anatomical planes. (From: Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy. General Anatomy and Musculoskeletal System. Illustrations by Voll M and Wesker K. © Thieme 2020.)

Terms of Movements

1.Flexion: It means forward bending of the trunk and folding of limbs.

2.Extension: In case of the trunk, it is backward or posterior bending and in limbs it is straightening.

3.Dorsiflexion: It is the movement of the foot toward the dorsum. It occurs at the ankle joint.

4.Plantar flexion: It is the movement of the foot toward the sole. It also occurs at the ankle joint.

5.Adduction: The movement toward the median plane.

6.Abduction: The movement away from the median plane.

7.Lateral flexion: It is movement of the trunk in the coronal plane.

8.Pronation and supination: These are movements involving the forearm and occur at the radioulnar joints (joints between the forearm bones, the radius and ulna). In anatomical position, the forearm is supinated and the palm faces forward. In pronation, the palm faces backwards/posteriorly.

9.Inversion and eversion: These movements involve the foot and occur at the subtalar and calcaneocuboid joints (joints of the tarsal bones, the bones of the foot). In inversion, the medial border of the foot is raised so that the sole faces medially. In eversion, the lateral border of the foot is raised and the sole of the foot faces laterally.

10.Rotation: The term signifies the movement where the part of the body is turned around its own longitudinal axis. In the limbs, it can be medial or lateral rotation at a particular joint, for example, the shoulder joint.

Structures That Are Encountered in Dissection

The body surface is covered by the skin, beneath which lies the superficial fascia and still deeper lies the deep fascia.

Skin

The skin consists of the outer, avascular, stratified, keratinized epithelium, the epidermis, and inner vascular, dense, fibrous tissue, the dermis. Dermis has protrusions into the epidermis. This increases the area of contact between them; thus, the two are firmly bound together.

Superficial Fascia

It consists of fat-filled fibrous mesh, connecting the dermis (of the skin) with the deep fascia. In the region of the scalp, palms of the hands, soles of the feet, and the back of the neck, the superficial fascia is dense. Hence, in these places the skin is firmly bounded to the underlying deep fascia. In other parts of the body, the superficial fascia is loose and elastic so that the skin can move freely.

The amount of fat in the superficial fascia varies. It is scanty in the nipple and areola of the breast and absent in some parts of the external genital organs. The subcutaneous fat is responsible for the rounded contours of the body and differs in its distribution in males and females. The superficial fascia contains the cutaneous blood vessels, lymphatics, and nerves.

At this stage, it is pertinent to understand how to differentiate between arteries, veins, and nerves. To accomplish this task, students should know the relationship of these structures to each other. It is well said, “Your eyes see the things that your mind knows.” Therefore, students are advised to go through the text to learn about the relationship between arteries, veins, and nerves.

Blood Vessels

The blood vessels comprise arteries and veins (Fig. 4). The arteries convey blood (oxygenated) from the heart to the tissues under high pressure. The arteries can be categorized as follows: (a) Large or elastic arteries, for example, the aorta, resist high internal pressure and their elastic recoil smoothens the intermittent systolic pumping action of the heart producing a continuous flow of blood. (b) The medium-sized arteries are also called muscular or distributing arteries. Their lumen is controlled by the sympathetic nerves, which determines the volume of blood to be distributed through them. (c) As the arteries branch and rebranch into finer vessels, the muscular tissue increases and the elastic elements reduce. The smallest among them, having diameter of less than 0.1 mm, are called arterioles. They then end up into capillaries.

The arteries during dissection look wiggly and maintain more or less circular shape.

Anastomosis found in many tissues form tubular loops through which some smaller arteries unite with each other. The anastomoses are found around joints, for example, the cubital anastomosis around the elbow joint. Anastomosis also occurs at the base of the brain, in the gastrointestinal tract, and at other sites. The importance of anastomosis is that it maintains the circulation when one of the arteries is blocked. Under these circumstances, the anastomosing channels enlarge to a considerable extent to establish collateral circulation. In some tissues, the extent of anastomosis between the adjacent arteries is scanty and hence blockage of such an artery results in death of the tissue supplied by it. Such arteries are called end arteries. This situation occurs in the brain, eyes, kidneys, lungs, etc.

Capillaries: The arterioles discharge blood through the microscopic tubes called capillaries into the tributaries of the veins. The capillary has a single layer of flat endothelial cells forming its wall. Through this thin wall, substances can be exchanged between the blood and tissues.

Fig. 4 Basic functional diagram of the circulatory system (no distinction is made between the systemic and pulmonary systems in the diagram). A, arteriole; C, arterial end of capillaries; LA, large artery; LV, large vein; MA, medium-sized artery; MV, medium-sized vein; SA, small artery; SV, small vein; V, venule. (From: Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy. General Anatomy and Musculoskeletal System. Illustrations by Voll M and Wesker K. © Thieme 2020.)

Arteriovenous anastomosis: In this, the capillaries do not exist and there is direct communication between the smaller arteries and veins. Such anastomoses exist in many exposed parts of the body, for example, the skin. A considerable amount of blood flows when this anastomosis opens. The increased blood flow permits greater transfer of heat without raising the metabolic rate of the tissue. This promotes heat loss from the skin.

Veins: The blood delivered to the tissue/organ through the arteries and capillaries is collected by the veins. The flow of blood in the veins is sluggish. This is because in each inspiration, there is a fall in intrathoracic pressure helping to draw air as well as venous blood into thorax and compression of veins by the surrounding muscles. Even a light compression can retard the blood flow in the veins because of low pressure within them. However, to prevent the backward flow of blood, veins are provided with valves. The position of these valves can be observed in the superficial veins of the forearm as localized swellings when the veins are distended with blood by compression at the elbow.

Venae comitantes: This refers to the veins that accompany deep arteries. This helps in maintaining the temperature of the venous blood as it returns to the heart. The surrounding muscles serve as pumps to direct the flow of blood through the veins. Once these deep veins are emptied by muscular contraction, they get filled again by the communications (perforators) between deep and superficial veins. The veins in cadavers tend to be collapsed/flattened.

Lymphatics and Lymph Nodes

Lymph nodes are small bean-shaped structures which are usually less than 12 mm across, that is, equal to size of a pea or baked bean. They are firm gland-like structures serving as filters for the lymph. Lymph is a clear fluid that flows through the lymph vessels. Lymphatics/Lymph vessels are fine tubes (Fig. 5). They are more in number in tissues closer to the epithelial surfaces, for example, the skin, the lining of the gastrointestinal tract, and respiratory epithelium. They are absent in the central nervous system. Lymph passes into the tissue through the capillary walls. It provides a medium of exchange of substances between the blood and tissues. It is drained by the lymph vessels. More lymph is produced in the active tissues and the inflamed tissues. In fact, the lymph capillaries collect lymph from the tissues and form plexus. They unite to form larger lymph vessels. The larger lymph vessels carry lymph to the lymph node. They are called afferent vessels. From the hilum of the lymph node, an efferent vessel carries it further. Lymph nodes vary in size. They produce lymphocytes. They are enlarged and become palpable when inflammation occurs in the areas/tissues they drain or when a tumor growth occurs in the tissue. They are particularly large in the groin and axilla. They are often associated with veins. They decrease in size in old age. Though the lymph vessels cannot be traced in cadaveric dissection except the largest one, that is, the thoracic duct, they are clinically important as they permit spread of infection or cancerous growth (tumors). In infection, the regional nodes are enlarged and become tender. In tumor/cancerous growth, the regional nodes become stony hard. Thus, they provide important information to the clinician about the disease process.

Fig. 5 Lymphatic system (lymphatics and lymph nodes). (From: Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy. General Anatomy and Musculoskeletal System. Illustrations by Voll M and Wesker K. © Thieme 2020.)

Nerves

The nerve cell along with its processes is called neuron. The cell body is called soma, the short processes are dendrites, and a single long process is called axon.

Nerves are pale-looking cords comprising a large number of thin filaments called nerve fibers. The nerve fiber is a process (axon) of the nerve cell (neuron) that carries nerve impulses away from nerve cell body to another neuron or with muscle or gland (Fig. 6). Each nerve fiber is surrounded by the endoneurium, a fibrous sheath. A collection of these fibers forms a fascicle/bundle which is surrounded by a sheath of cells and fibers. It is called the perineurium (Fig. 7). Many such fascicles form the nerve which is surrounded by a sheath called the epineurium. These fibrous tissue coverings confer considerable tensile strength to the delicate nerve fibers. The large nerve fiber is enclosed in a sheath cell (Schwann cell) which forms a series of concentric layers of discontinuous, laminated, fatty sheath around the fiber. This is the myelin sheath. The thin nerve fiber is simply enclosed in sheath cells which do not form concentric layers. They are called the unmyelinated nerve fibers (Fig. 7).

Fig. 6 Typical neuron. (From: Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy. General Anatomy and Musculoskeletal System. Illustrations by Voll M and Wesker K. © Thieme 2020.)

Fig. 7 Structure of a peripheral nerve. (From: Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy. General Anatomy and Musculoskeletal System. Illustrations by Voll M and Wesker K. © Thieme 2020.)

The nerve fibers transmit nerve impulses from the central nervous system to the various parts/tissues of the body or from these structures to the central nervous system. Among these fibers, those that carry impulses from the central nervous system to the peripheral structures are called the efferent fibers. Some of them pass to the muscles. They are called the motor nerve fibers. The fibers which carry impulses to the central nervous system are called the afferent nerve fibers/sensory nerve fibers. They carry sensory impulses, for example, sensations of pain, touch, and temperature from the skin and other tissues to the central nervous system.

The nerves are broadly classified into (a) cranial nerves which are attached to the brain and (b) spinal nerves which arise from the spinal cord.

Spinal nerves: There are 31 pairs of the spinal nerves. These are cervical (8), thoracic (12), lumbar (5), sacral (5), and coccygeal (1). They emerge through the intervertebral foramina. All of them emerge caudal to the corresponding vertebra except the cervical nerves which emerge cranial to the corresponding vertebra. The first seven cervical nerves are cranial to the corresponding vertebra and the eighth cervical nerve passes below the seventh cervical, that is, between it and the first thoracic vertebra. Each spinal nerve is attached to the spinal cord by two roots, the ventral and dorsal (Fig. 8).

Fig. 8 Typical spinal nerve. G, dorsal root ganglion; GR, gray ramus communicans.

Ventral root consists of efferent fibers that arise from the nerve cells in the spinal cord. The dorsal root is a bundle of afferent fibers. Along the dorsal root, there is a collection of nerve cells that forms a swelling called the dorsal root ganglion. The fibers of the dorsal root are derived from these cells as their central processes while the peripheral process enters the spinal nerve. The two roots unite at the dorsal root ganglion in the intervertebral foramen. This forms the main trunk of the spinal nerve which is short and has a mixture of both the afferent and efferent fibers. It then divides into a ventral ramus and a dorsal ramus.

The dorsal ramus is smaller and it passes backwards in the muscles of the back (erector spinae). It then divides into medial and lateral branches which supply the muscle and also the overlying skin. These cutaneous branches are placed in a row on each side of the midline on the back.

The larger ventral ramus runs laterally. In the thoracic region, the ventral rami run along the lower border of the corresponding ribs and form the intercostal and subcostal nerves. Each of them supplies the muscles (intercostal muscles) and gives an anterior and lateral cutaneous branch supplying the strip of the skin designated as dermatome. Dermatome is the strip of the skin supplied by a single spinal nerve (Fig. 8). The muscle mass supplied by a single spinal nerve is called the myotome.

The ventral rami in the cervical, lumbar, sacral, and coccygeal regions form the nerve plexuses, that is, the cervical and brachial plexuses that later supply the upper limb. The ventral rami of the lumbar and sacral regions contribute to form the plexuses which supply the lower limb. Each ventral ramus receives a slender gray ramus communicans from the corresponding ganglion of the sympathetic chain/trunk.

The sympathetic chain/trunk is formed by the ganglia arranged in a vertical row and connected by nerve fibers. They extend from the base of the skull to the coccyx. They run on each side of the vertebral column. The nerve fibers in the gray ramus arise from the nerve cells (neurons) of the sympathetic ganglia. These are the postganglionic fibers; they pass into the ventral ramus to be distributed through its branches. Through the ventral ramus, some fibers enter the dorsal ramus and are distributed through its branches. These sympathetic nerve fibers supply the muscular element in the wall of blood vessels, arrectores pilorum (associated with the hair follicle), and sweat glands.

In the thoracic and upper lumbar (L1–L3), ventral roots and the rami have myelinated fibers which pass from the ventral ramus to the sympathetic ganglion. These are the preganglionic fibers and they constitute white rami communicans. These fibers run longitudinally. Through them, the central nervous system controls the activity of the sympathetic nerve cells in the sympathetic chain. Thus, the central nervous system can control the amount of blood flowing through various tissues, the secretions of the sweat glands, gooseflesh by action on arrectores pilorum, etc.

Note that the cutaneous nerve supplying the skin is not only entirely sensory but also has sympathetic efferent fibers in it. Likewise, a branch given to a muscle is not entirely motor but contains sensory and sympathetic fibers. Therefore, a nerve injury not only results in paralysis of the muscle but also leads to the loss of sensation, sweating, goose flesh, and control of blood vessels.

Apart from the gray rami communicans, the sympathetic trunk sends postganglionic fibers which pass along the arteries of the limbs, head, and neck and also the body wall. The postganglionic sympathetic fibers also supply the viscera (internal organs) through the periarterial plexus of nerve fibers.

The parasympathetic nervous system supplies the viscera and the eye. This system comprises the peripheral ganglia located in or close to the viscera which they supply. It innervates glands and the smooth muscles of the gastrointestinal tract. This is done by releasing acetylcholine from the terminals of the cholinergic nerve fibers. Similarly, the sympathetic postganglionic fibers are called the adrenergic fibers.

The parasympathetic nervous system has the craniosacral outflow, whereas the sympathetic system has the thoracolumbar outflow. They together form the autonomic nervous system.