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Anatomy Second Edition
EUGENE C.TOY, MD The John S. Dunn, Senior Academic Chief and Program Director The Methodist Hospital-Houston Obstetrics and Gynecology Residency Program Houston,Texas Clerkship Director, Clinical Associate Professor Department of Obstetrics and Gynecology University of Texas Medical School at Houston Houston,Texas
LAWRENCE M. ROSS, MD, PHD Adjunct Professor Department of Neurobiology and Anatomy University of Texas Medical School at Houston Houston,Texas
LEONARD J. CLEARY, PHD Senior Lecturer Department of Neurobiology and Anatomy Course Director, Gross Anatomy University of Texas Medical School at Houston Houston,Texas
CRISTO PAPASAKELARIOU, MD, FACOG Clinical Professor, Department of Obstetrics and Gynecology University of Texas Medical Branch Galveston,Texas Clinical Director of Gynecologic Surgery St. Joseph Medical Center Houston,Texas
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Hitoshi “Toshi” Nikaidoh (1968–2003)
We dedicate this book to our dear friend, Dr. Toshi Nikaidoh, who led by example, always beyond the call of duty and along the way, taught so many of us about so many important things about life.
As a surgeon-to-be, he tutored fellow lower-level medical students not only how to master the challenges of gross anatomy, but also how to develop the skillful art of dis- section and respect for the human body.
As a spiritual leader, he taught his youth group not only the meaning of good fel- lowship by recalling good times spent on missionary travels abroad, but also the value of good worship by sharing his faith along the way.
As a physician, he taught patients not only to hope when all hope is lost, but also to have faith through which peace can be found.
And as a friend, son, brother, or just that smiling doctor in the hallway with the bow tie, he taught us how truly possible it is for one person to make a world of difference.
Toshi’s dedication to academics and education, his compassion for the sick and less fortunate, and his tireless devotion to his faith, family, and friends have all continued to touch and change lives of all who knew him and even of all who only knew of him.
Miki Takase, MD Fellow classmate,
University of Texas Medical School at Houston St. Joseph Medical Center Ob/Gyn Resident
Written in behalf of Toshi’s many friends, classmates, fellow residents, staff, and faculty at
University of Texas Medical School at Houston and St. Joseph Medical Center
In the memory of Dr. Hitoshi Nikaidoh, who demonstrated unselfishness, love for his fellow man, and compassion for everyone around him.
He is the best example of the physician healer, and we were blessed to have known him.
To my wife, Irene; the children, Chip, Jennifer, Jocelyn, Tricia, and Trey; and the medical students,
each of whom has taught me something of value.
For the students at the University of Texas Medical School at Houston, with thanks to Dr. John Byrne for his support of the Human Structure Facility.
To my parents Kiriaki and Alexander, and my wife Beth, for their support, love, and encouragement.
Applying Basic Sciences to Clinical Situations 1
Clinical Cases 7
Fifty-three Case Scenarios 9
Listing of Cases 353
Listing by Case Number 355 Listing by Disorder (Alphabetical) 356
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John E. Bertini, Jr., MD, FACS Academic Chief Department of Urology St. Joseph Medical Center Houston, Texas Benign Prostatic Hypertrophy Testicular Cancer
Konrad P. Harms, MD Associate Program Director Obstetrics and Gynecology Residency Program The Methodist Hospital-Houston Houston, Texas Clinical Assistant Professor Weill Cornell School of Medicine New York, New York Greater Vestibular Gland Abscess
Lauren Giacobbe, MD Resident in Obstetrics and Gynecology The Methodist Hospital-Houston Houston, Texas Ectopic Pregnancy
Christie S. Keil Medical Student, Class of 2008 University of Texas Medical School at Houston Houston, Texas Carotid Insufficiency Suprarenal (Adrenal) Tumors
Lindsey Kelly Medical Student, Class of 2008 University of Texas Medical School at Houston Houston, Texas Ectopic Pregnancy Greater Vestibular Gland
Vian Nguyen, MD Resident in Obstetrics and Gynecology The Methodist Hospital-Houston Houston, Texas Cephalohematoma Cervical Cancer
Jeané Simmons Holmes, MD, FACOG Assistant Clinical Professor Weill Cornell School of Medicine New York, New York Obstetrics and Gynecology Residency Program The Methodist Hospital-Houston Houston, Texas Cervical Cancer
Brad Blachly Swelstad, MD Chief Resident in Obstetrics and Gynecology The Methodist Hospital-Houston Houston, Texas Injury to Inferior Epigastric Artery
Thomas V. Taylor, MD, FACS, FRCS Academic Chief of Surgery St. Joseph Medical Center Houston, Texas Acute Appendicitis Inguinal Hernia
Kathryn A. Winslow, MD Resident in Obstetrics and Gynecology The Methodist Hospital-Houston Houston, Texas Pulmonary Embolism
vi i i CONTRIBUTORS
The inspiration for this basic science series occurred at an educational retreat led by Dr. Maximillian Buja, who at the time was the Dean of the medical school. Dr. Buja, served as Dean of the University of Texas Medical School at Houston from 1995 to 2003, before being appointed Executive Vice President for Academic Affairs. It has been such a joy to work together with Drs. Len Cleary and Lawrence Ross, who are brilliant anatomists and teachers. Sitting side by side during the writing process as they precisely described the anatom- ical structures was academically fulfilling, but more so, made me a better sur- geon. It has been a privilege to work with Dr. Cristo Papasakelariou, a dear friend, scientist, leader, and the finest gynecological laparoscopic surgeon I know. I would like to thank McGraw-Hill for believing in the concept of teach- ing by clinical cases. I owe a great debt to Catherine Johnson, who has been a fantastically encouraging and enthusiastic editor. I greatly appreciate the tal- ented, thorough and insightful review by Christie Keil, a fourth year medical student. Drs. Cleary and Ross would like to acknowledge the figure drawings from the University of Texas Medical School at Houston originally published in Philo et al., Guide to Human Anatomy. Philadelphia: Saunders, 1985. At Methodist Hospital, I appreciate Drs. Mark Boom, Karin Pollock-Larsen, H. Dirk Sostman, and Judy Paukert, and Mr. John Lyle and Mr. Reggie Abraham. At St. Joseph Medical Center, I would like to recognize our outstanding administrators: Phil Robinson, Pat Mathews, Laura Fortin, Dori Upton, Cecile Reynolds, and Drs. John Bertini and Thomas V. Taylor. I appreciate Marla Buffington’s advice and assistance. Without the help from my colleagues, Drs. Sam Law, Eric Haufrect, Keith Reeves, and Waverly Peakes, this manu- script could not have been written. Most importantly, I am humbled by the love, affection, and encouragement from my lovely wife, Terri, and our four children, Andy, Michael, Allison, and Christina.
Eugene C. Toy
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Mastering the diverse knowledge within a field such as anatomy is a formida- ble task. It is even more difficult to draw on that knowledge, relate it to a clin- ical setting, and apply it to the context of the individual patient. To gain these skills, the student learns best with good anatomical models or a well-dissected cadaver, at the laboratory bench, guided and instructed by experienced teach- ers, and inspired toward self-directed, diligent reading. Clearly, there is no replacement for education at the bench. Even with accurate knowledge of the basic science, the application of that knowledge is not always easy. Thus, this collection of patient cases is designed to simulate the clinical approach and stress the clinical relevance to the anatomical sciences.
Most importantly, the explanations for the cases emphasize the mechanisms and structure–function principles, rather than merely rote questions and answers. This book is organized for versatility to allow the student “in a rush” to go quickly through the scenarios and check the corresponding answers or to consider the thought-provoking explanations. The answers are arranged from simple to complex: the bare answers, a clinical correlation of the case, an approach to the pertinent topic including objectives and definitions, a compre- hension test at the end, anatomical pearls for emphasis, and a list of references for further reading. The clinical vignettes are listed by region to allow for a more synthetic approach to the material. A listing of cases is included in Section III to aid the student who desires to test his/her knowledge of a certain area or to review a topic including basic definitions. We intentionally used open-ended questions in the case scenarios to encourage the student to think through relations and mechanisms.
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S E C T I O N I
Applying Basic Sciences to Clinical Situations
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APPROACH TO LEARNING
Learning anatomy is not just memorization. It is the visualization of the rela- tions between the various structures of the body and the understanding of their corresponding functions. Rote memorization will lead to quick forget- fulness and boredom. Instead, the student should approach an anatomical structure by trying to correlate its purpose with its design. Structures that are close together should be related not only spatially but also functionally. The student should also try to project clinical significance to the anatomical find- ings. For example, if two nerves travel close together down the arm, one could speculate that a tumor, laceration, or ischemic injury might affect both nerves; the next step would be to describe the deficits expected on the physical exami- nation.
The student must approach the subject in a systematic manner, by studying the skeletal relations of a certain region of the body, the joints, the muscular system, the cardiovascular system (including arterial perfusion and venous drainage), the nervous system (such as sensory and motor neural innerva- tions), and the skin. Each bone or muscle is unique and has advantages due to its structure and limitions or perhaps vulnerability to specific injuries. The stu- dent is encouraged to read through the description of the anatomical relation in a certain region, correlate the illustrations of the same structures, and then try to envision the anatomy in three dimensions. For instance, if the anatomi- cal drawings are in the coronal plane, the student may want to draw the same region in the sagittal or cross-sectional plane as an exercise to visualize the anatomy more clearly.
Anatomical position: The basis of all descriptions in the anatomical sci- ences, with the head, eyes, and toes pointing forward, the upper limbs by the side with the palms facing forward, and the lower limbs together.
Anatomical planes: A section through the body, one of four commonly described planes. The median plane is a single vertically oriented plane dividing the body into right and left halves, whereas the sagittal planes are oriented parallel to the median plane but not necessarily in the mid- line. Coronal planes are perpendicular to the median plane and divide the body into anterior (front) and posterior (back) portions. Transverse, axial, or cross-sectional planes pass through the body perpendicular to the median and coronal planes and divide the body into upper and lower parts.
Directionality: Superior (cranial) is toward the head, whereas inferior (caudal) is toward the feet; medial is toward the midline, whereas lat- eral is away from the midline. Proximal is toward the trunk or attach- ment, whereas distal is away from the trunk or attachment. Superficial is near the surface, whereas deep is away from the surface.
APPLYING BASIC SCIENCES TO CLINICAL SITUATIONS 3
Motion: Adduction is movement toward the midline, whereas abduction is movement away from the midline. Extension is straightening a part of the body, whereas flexion is bending the structure. Pronation is the action of rotating the palmar side of the forearm facing posteriorly, whereas supination is the action of rotating the palmar side of the fore- arm anteriorly.
APPROACH TO READING
The student should read with a purpose and not merely to memorize facts. Reading with the goal of comprehending the relation between structure and function is one of the keys to anatomy. Also, being able to relate the anatomi- cal sciences to the clinical picture is critical. Thus, there are seven key ques- tions that help to stimulate the application of basic science information to the clinical setting.
1. Given the importance of a certain required function, which anatom- ical structure provides the ability to perform that function?
2. Given the anatomical description of a body part, what is its function? 3. Given a patient’s symptoms, what structure is affected? 4. Which lymph nodes are most likely to be affected by cancer at a
particular location? 5. If an injury occurs to one part of the body, what is the expected
clinical manifestation? 6. Given a deficit such as weakness or numbness, what other symp-
toms or signs would the patient most likely have? 7. What is the male or female homologue to the organ in question?
1. Given the importance of a certain required function, which anatom- ical structure provides the ability to perform that function?
The student should be able to relate the anatomical structure to a function. When approaching the upper extremity, for instance, the stu- dent may begin with the statement, “The upper extremity must be able to move in many different directions to be able to reach up (flexion), reach backward (extension), reach to the side (abduction), bring the arm back (adduction), or turn a screwdriver (pronation/supination).” Because of the need for the upper extremity to move in all these direc- tions, the joint between the trunk and arm must be very versatile. Thus, the shoulder joint is a ball-and-socket joint to allow the movement in the different directions required. Further, the shallower the socket is, the more mobility the joint has. However, the versatility of the joint makes its dislocation easier.
2. Given the anatomical description of a body part, what is its function? This is the counterpart to the previous question regarding the relation
between function and structure. The student should try to be imaginative
4 CASE FILES: ANATOMY
and not just accept the “textbook” information. One should be inquisi- tive, perceptive, and discriminating. For example, a student might spec- ulate about why bone marrow is in the middle of bones instead of the bones being solid. The student might speculate as follows: “The main purpose of bones is to support the body and protect various organs. If the bones were solid, they might be slightly stronger, but they would be much heavier and be a detriment to the body. Also, production of blood cells is a critical function of the body. Thus, by having the marrow within the center of the bone, the process is protected.”
3. Given a patient’s symptoms, what structure is affected? This is one of the most critical questions of clinical anatomy. It is also
one of the major questions a clinician must answer when evaluating a patient. In clinical problem solving, the physician elicits information by asking questions (taking the history) and performing a physical exami- nation while making observations. The history is the single most impor- tant tool for making a diagnosis. A thorough understanding of the anatomy aids the clinician tremendously because most diseases affect body parts under the skin and require “seeing under the skin.” For exam- ple, the clinical data may be: “a 45-year-old woman complains of numb- ness of the perineal area and has difficulty voiding.” The student may go through the following thinking process: “The sensory innervation of the perineal area is through sacral nerves S2 through S4, and control of the bladder is through the parasympathetic nerves, also S2 through S4. Therefore, two possibilities are a spinal cord problem involving those nerve roots or a peripheral nerve lesion. The internal pudendal nerve innervates the perineal region and is involved with micturition.” Further information is supplied: “The patient states that she has had back pain since falling down 2 weeks ago.” Now the lesion can be isolated to the spine, most likely the cauda equina (horse’s tail), which is a bundle of spinal nerve roots traversing through the cerebrospinal fluid.
4. Which lymph nodes are most likely to be affected by cancer at a particular location?
The lymphatic drainage of a particular region of the body is impor- tant because cancer may spread through the lymphatics, and lymph node enlargement may occur due to infection. The clinician must be aware of these pathways to know where to look for metastasis (spread) of cancer. For example, if a cancer is located on the vulva labia majora (or the scrotum in the male), the most likely lymph node involved is the superficial inguinal nodes. The clinician would then be alert to palpat- ing the inguinal region for lymph node enlargement, which would indi- cate an advanced stage of cancer and a worse prognosis.
5. If an injury occurs to one part of the body, what is the expected clinical manifestation?
If a laceration, tumor, trauma, or bullet causes injury to a specific area of the body, it is important to know which crucial bones, muscles,
APPLYING BASIC SCIENCES TO CLINICAL SITUATIONS 5
joints, vessels, and nerves might be involved. Also, based on experi- ence, the clinician is aware of particular vulnerabilities. For example, the thinnest part of the skull is located in the temple region, and under- neath this is the middle meningeal artery. Thus, a blow to the temple region may be disastrous. A laceration to the middle meningeal artery would lead to an epidural hematoma because this artery is located superficial to the dura and can cause cerebral damage.
6. Given a deficit such as weakness or numbness, what other symp- toms or signs would the patient most likely have?
This requires a three-step process in analysis. First, the student must be able to deduce the initial injury based on the clinical findings. Second, a determination must be made of the probable site of injury. Third, the student must make an educated guess as to which other structures are in close proximity and, if injured, what the clinical man- ifestations would be. To be more skilled in learning these relations, one can begin from a clinical finding, propose an anatomical deficit, pro- pose a mechanism or location of the injury, identify another nerve or vessel or muscle in that location, propose the new clinical finding, and so on.
7. What is the male or female homologue to the organ in question? This knowledge of homologous correlates is important to under-
stand the embryologic relations and, hence, the resultant anatomical relations. By being aware of the female and male homologues, fewer structures need to be memorized because analogous relations are eas- ier to learn than two separate structures. For example, the vascular sup- plies of homologous structures are usually similar. The ovarian arteries arise from the abdominal aorta below the renal arteries; likewise, the testicular arteries arise from the abdominal aorta.
• The student should approach an anatomical structure by visualizing the structure and understanding its function.
• A standard anatomical position is used as a reference for anatomical planes and terminology of movement.
• There are seven key questions to stimulate the application of basic sci- ence information to the clinical arena.
Moore KL, Dalley AF. Clinically oriented anatomy, 5th ed. Baltimore, MD: Lippincott Williams & Wilkins, 2006.
6 CASE FILES: ANATOMY
S E C T I O N I I
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❖ CASE 1
A 32-year-old woman delivered a large (4800 g) baby vaginally after some dif-
ficulty with her labor. Her prenatal course was complicated by diabetes, which
occurred during pregnancy. At delivery, the infant’s head emerged, but the
shoulders were “stuck” behind the maternal symphysis pubis, requiring the
obstetrician to apply some effort and maneuvers to free up the infant’s shoul-
ders and complete the delivery. The infant was noted to have a good cry and
pink color but was not moving its right arm.
◆ What is the most likely diagnosis?
◆ What is the most likely etiology for this condition?
◆ What is the likely anatomical mechanism for this disorder?
ANSWERS TO CASE 1: BRACHIAL PLEXUS INJURY
Summary: A large (4800 g) infant of a diabetic mother is delivered after some difficulty and cannot move its right arm. There is a shoulder dystocia (the infant’s shoulders are stuck after delivery of the head).
◆ Most likely diagnosis: Brachial plexus injury, probably Erb palsy
◆ Most likely etiology for this condition: Stretching of the upper brachial plexus during delivery
◆ Likely anatomical mechanism for this disorder: Stretching of nerve roots C5 and C6 by an abnormal increase in the angle between the neck and the shoulder
During delivery, particularly of a large infant, shoulder dystocia may occur. In this situation, the fetal head emerges, but the shoulders become wedged behind the maternal symphysis pubis. An obstetrician will use maneuvers such as flex- ion of the maternal hips against the maternal abdomen (McRobert maneuver) or fetal maneuvers such as pushing the fetal shoulders into an oblique position. These actions are designed to allow delivery of the fetal shoulders without excessive traction on the fetal neck. Despite such carefully executed maneu- vers, infants may be born with stretch injuries to the brachial plexus, resulting in nerve palsies. The most common of these is an upper brachial plexus stretch injury in which nerve roots C5 and C6 are affected, resulting in the infant’s arm being limp and to its side. Most such injuries resolve spontaneously.
APPROACH TO THE BRACHIAL PLEXUS
1. Be able to describe the spinal cord segments, named terminal branches, and the motor and sensory deficits of an upper brachial plexus injury.
2. Be able to describe the mechanism, spinal cord segments, named ter- minal branches, and the motor and sensory deficits of a lower brachial plexus injury.
3. Be able to describe the mechanism, spinal cord segments, named ter- minal branches, and the motor and sensory deficits with cord injury of the brachial plexus.
Brachial plexus: A major peripheral nerve network formed by the anterior primary rami of the fifth cervical to the first thoracic spinal nerves.
10 CASE FILES: ANATOMY
Upper brachial plexus injury: Typically involves nerve roots C5 and C6, resulting in the upper limb hanging at the side, with medial rotation and the palm facing posteriorly.
Lower brachial plexus injury: Less common injury involving C8 through T1 and the ulnar nerve, leading to interosseous muscle atrophy and claw hand.
Shoulder dystocia: Condition whereby the fetal head delivers vaginally, but the shoulders are impacted behind the maternal bony pelvis.
The brachial plexus arises from the inferior portion of the cervical spinal cord enlargement. It is formed by the ventral primary rami of spinal nerves C5 through C8 and most of T1. The network of nerves that form the brachial plexus is divided anatomically from proximal (medial) to distal (lateral) into roots, trunks, divisions, cords, and terminal branches (mnemonic: Randy Travis Drinks Cold Texas Beer). The roots of the plexus emerge from between the anterior and middle scalene muscles together with the subclavian artery. Arising from the roots are branches to the longus colli and scalene mus- cles and the dorsal scapular and long thoracic nerves. The roots unite to form superior, middle, and inferior trunks. The suprascapular nerve and the nerve to the subclavius muscle arise from the superior trunk. Each trunk is divided into anterior and posterior divisions, which will innervate muscula- ture of the anterior and posterior compartments, respectively (Figure 1-1).
The anterior divisions of the superior and middle trunks unite to form the lateral cord. The lateral cord gives off the lateral pectoral nerve. The ante- rior division of the inferior trunk continues distally as the medial cord, whose branches are the medial pectoral, medial brachial cutaneous, and medial antebrachial cutaneous nerves. The posterior divisions of all three trunks unite to form the posterior cord, and its branches are the upper and lower subscapular and thoracodorsal nerves. The three cords are named for their relation to the axillary artery, which passes through the plexus at this level. The terminal branches of the brachial plexus are the axillary, musculocuta- neous, median, ulnar, and radial nerves.
The axillary nerve (C5 and C6) arises from the posterior cord and courses posteriorly around the surgical neck of the humerus, where it is at risk of injury. The posterior circumflex humeral artery accompanies the nerve in this course. The axillary nerve supplies the deltoid and teres minor muscles, is sensory to the skin over the lower portion of the deltoid, and is optimally tested on the “shoulder patch” portion of the upper arm. Axillary nerve injury such as by fracture at the surgical neck of the humerus results in an inability to abduct the arm at the shoulder to a horizontal position and sensory loss in the shoulder patch area (Figure 1-2).
The musculocutaneous nerve (C5–C7) is the continuation of the lateral cord. It courses distally through the coracobrachialis muscle to innervate it in
CLINICAL CASES 11
12 CASE FILES: ANATOMY
Second intercostal nerve
First intercostal nerve
Thoracodorsal nerve (6–7–8)
Medial antebrachial cutaneous nerve (8–1)
Medial brachial cutaneous nerve (T1)
Ulnar nerve (8–1)
Median nerve (5–6–7–8–1)
Musculocutaneous nerve (4–5–6)
To phrenic nerve
Dorsal scapular nerve (5)To subclavius
Suprascapular nerve (4–5–6)
Late ral c
or d iv.
. d iv
. Mid dle
Lon g th
ner ve (
Lower trunk Subs
r co rdLate
Med ial c
To scaleni and longus colli muscles
Nerves or plexus roots
Post div. (5–6)
Splitting of the plexus into anterior and posterior divisions is one of the most significant features in the redistribution of nerve fibers, because it is here that fibers supplying the flexor and extensor groups of muscles of the upper extremity are separated. Similar splitting is noted in the lumbar and sacral plexuses for the supply of muscles of the lower extremity.
Figure 1-1. The brachial plexus. (Reproduced, with permission, from Waxman SG. Clinical Neuroanatomy, 25th ed. New York: McGraw-Hill, 2003:348.)