CLINICAL ANATOMY BY REGIONS N I N T H E D I T I O N C L I N I C AL A N A T O MY BY R E G I O NS Richard ร. Snell, M.R.C.S., L.R.C.P., M.B., B.S., M.D., Ph.D. Emeritus Professor of Anatomy (formerly Chairman of the Department of Anatomy) George Washington University School of Medicine and Health Sciences Washington, District of Columbia Previously Associate Professor of Anatomy and Medicine, Yale University Medical School Lecturer in Anatomy, King's College, University of London Visiting Professor of Anatomy, Harvard Medical School Acquisitions Editor: Crystal Taylor Product Manager: Julie Montalbano Marketing Manager: Joy Fisher Williams Designer: Steve Druding Compositor: SPi Global 9th Edition Copyright © 2012, 2008, 2004 Lippincott Williams & Wilkins, a Wolters Kluwer business. 351 West Camden Street Two Commerce Square Baltimore, MD 21201 2001 Market Street Philadelphia, PA 19103 Printed in China All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright. To request permission, please con- tact Lippincott Williams & Wilkins at Two Commerce Square, 2001 Market Street, Philadelphia, PA 19103, via email at [email protected], or via website at lww.com (products and services). Library of Congress Cataloging-in-Publication Data Snell, Richard S. Clinical anatomy by regions / Richard S. Snell. – 9th ed. p. ; cm. Includes index. ISBN 978-1-60913-446-4 1. Human anatomy. I. Title. [DNLM: 1. Anatomy, Regional. 2. Body Regions—anatomy & histology. QS 4] QM23.2.S55 2012 612—dc23 2011020326 DISCLAIMER Care has been taken to confirm the accuracy of the information present and to describe generally accepted practices. However, the authors, editors, and publisher are not responsible for errors or omissions or for any consequences from application of the information in this book and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the con- tents of the publication. Application of this information in a particular situation remains the profes- sional responsibility of the practitioner; the clinical treatments described and recommended may not be considered absolute and universal recommendations. The authors, editors, and publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accordance with the current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new or infrequently employed drug. Some drugs and medical devices presented in this publication have Food and Drug Administration (FDA) clearance for limited use in restricted research settings. It is the responsibility of the health care provider to ascertain the FDA status of each drug or device planned for use in their clinical practice. To purchase additional copies of this book, call our customer service department at (800) 638-3030 or fax orders to (301) 223-2320. International customers should call (301) 223-2300. Visit Lippincott Williams & Wilkins on the Internet: http://www.lww.com. Lippincott Williams & Wilkins customer service representatives are available from 8:30 am to 6:00 pm, EST. 9 8 7 6 5 4 3 2 1 P R E F A C E This book provides medical students, dental students, allied 3. Basic Clinical Anatomy: This section provides basic health students, and nursing students with a basic knowl- information on gross anatomic structures that are of edge of anatomy that is clinically relevant. clinical importance. Numerous examples of normal In this new edition, further efforts have been made to radiographs, CT scans, MRI studies, and sonograms are weed out unnecessary material and reduce the size of the also provided. Labeled photographs of cross-sectional text. The following changes have been introduced. anatomy of the head, neck, and trunk are included to stimulate students to think in terms of three-dimen- 1. The text and tables have been reviewed and trimmed sional anatomy, which is so important in the interpreta- where necessary. tion of imaging studies. 2. All the illustrations have been reviewed and some have been discarded where duplication occurs. 4. Surface Anatomy: This section provides surface land- 3. The anatomy of common medical procedures has marks of important anatomic structures, many of which been carefully reviewed. Sections on the complica- are located some distance beneath the skin. This section tions caused by the ignorance of normal anatomy is important because most practicing medical personnel have been retained. seldom explore tissues to any depth beneath the skin. 4. The Clinical Problems and Review Questions are 5. Clinical Problem Solving and Review Questions: available online at www.thePoint.lww.com/Snell9e Available online at www.thePoint.lww.com, the Each chapter of Clinical Anatomy is constructed in a purpose of these questions is threefold: to focus atten- similar manner. This gives students ready access to mate- tion on areas of importance, to enable students to assess rial and facilitates moving from one part of the book to their areas of weakness, and to provide a form of self- another. Each chapter is divided into the following catego- evaluation for questions asked under examination con- ries: ditions. Many of the questions are centered around a clinical problem that requires an anatomic answer. 1. Clinical Example: A short case report that dramatizes the relevance of anatomy in medicine introduces each To assist in the quick understanding of anatomic facts, chapter. the book is heavily illustrated. Most figures have been kept simple, and color has been used extensively. Illustrations 2. Chapter Objectives: This section focuses the student on summarizing the nerve and blood supply of regions have the material that is most important to learn and under- been retained, as have overviews of the distribution of cra- stand in each chapter. It emphasizes the basic structures nial nerves. in the area being studied so that, once mastered, the stu- dent is easily able to build up his or her knowledge base. This section also points out structures on which exam- R.S.S. iners have repeatedly asked questions. v A C K N O W L E D G M E N T S I wish also to express my sincere thanks to Terry Dolan, Virginia Childs, Myra Feldman, and Ira Grunther for preparation of the artwork. I am most grateful to Dr Larry Wineski (Professor of Anatomy at Morehouse School of Medicine) and Dr Wayne Lambert (Associate Professor of Anatomy at West Virginia University School of Medicine) for carefully looking through the Clinical Problem Solving Questions (located online) and making sure that they conform to the format used in the board examinations. Finally, I wish to express my deep gratitude to the staff of Lippincott Williams & Wilkins for their great help and support in the preparation of this new edition. vii