UEU-co logo

4.htm

Chapter 4 The Abdomen: Part I—The Abdominal Wall A 26-year-old man complaining of a painful swelling in the right groin was seen by his physician; he had vomited four times in the previous 3 hours. On examination, he was dehydrated and his abdomen was moderately distended. A large, tense swelling, which was very tender on palpation, was seen in the left groin and extended down into the scrotum. An attempt to gently push the contents of the swelling back into the abdomen was impossible. A diagnosis of a right complete, irreducible, indirect inguinal hernia was made. The vomiting and abdominal distention were secondary to the intestinal obstruction caused by the herniation of some bowel loops into the hernial sac. An indirect inguinal hernia is caused by a congenital persistence of a sac formed from the lining of the abdomen. This sac has a narrow neck, and its cavity remains in free communication with the abdominal cavity. Hernias of the abdominal wall are common. It is necessary to know the anatomy of the abdomen in the region of the groin before one can make a diagnosis or understand the different hernial types that can exist. Moreover, without this knowledge it is impossible to appreciate the complications that can occur or to plan treatment. A hernia may start as a simple swelling, but it can end as a life-threatening problem. Chapter Objectives

  • Acute abdominal pain, abdominal swellings, and blunt and penetrating trauma to the abdominal wall are common problems facing the physician. The problems are complicated by the fact that the abdomen contains multiple organ systems, and knowing the spatial relationships of these organs to one another and to the anterior abdominal wall is essential before an accurate and complete diagnosis can be made.
  • The abdominal wall is a flexible structure through which the physician can often feel diseased organs that lie within the abdominal cavity. An intact abdominal wall is essential for the support of the abdominal contents. A defect or malfunction of the wall can allow the abdominal contents to bulge forward and form a hernia. The abdominal wall provides the surgeon with a site for access to deep-lying diseased structures.
  • For the above reasons, the anatomy of the anterior abdominal wall must be learned in detail. Because of its great clinical importance, examiners ask many questions in this area.

P.146
Basic Anatomy The abdomen is the region of the trunk that lies between the diaphragm above and the inlet of the pelvis below. Structure of the Anterior Abdominal Wall The anterior abdominal wall is made up of skin, superficial fascia, deep fascia, muscles, extraperitoneal fascia, and parietal peritoneum. Skin The skin is loosely attached to the underlying structures except at the umbilicus, where it is tethered to the scar tissue. The natural lines of cleavage in the skin are constant and run downward and forward almost horizontally around the trunk. The umbilicus is a scar representing the site of attachment of the umbilical cord in the fetus; it is situated in the linea alba (see below). Clinical Notes Surgical Incisions If possible, all surgical incisions should be made in the lines of cleavage where the bundles of collagen fibers in the dermis run in parallel rows. An incision along a cleavage line will heal as a narrow scar, whereas one that crosses the lines will heal as wide or heaped-up scars. Clinical Notes Infection of the Umbilicus In the adult, the umbilicus often receives scant attention in the shower and is consequently a common site of infection. P.147
Nerve Supply The cutaneous nerve supply to the anterior abdominal wall is derived from the anterior rami of the lower six thoracic and the first lumbar nerves (see Fig. 4-16). The thoracic nerves are the lower five intercostal and the subcostal nerves; the first lumbar nerve is represented by the iliohypogastric and the ilioinguinal nerves. The dermatome of T7 is located in the epigastrium over the xiphoid process. The dermatome of T10 includes the umbilicus, and that of L1 lies just above the inguinal ligament and the symphysis pubis. The dermatomes and distribution of cutaneous nerves are shown in Figure 4-16. Blood Supply Arteries The skin near the midline is supplied by branches of the superior and the inferior epigastric arteries. The skin of the flanks is supplied by branches of the intercostal, the lumbar, and the deep circumflex iliac arteries (see Fig. 4-15). In addition, the skin in the inguinal region is supplied by the superficial epigastric, the superficial circumflex iliac, and the superficial external pudendal arteries, branches of the femoral artery.

Figure 4-1 A. Arrangement of the fatty layer and the membranous layer of the superficial fascia in the lower part of the anterior abdominal wall. Note the line of fusion between the membranous layer and the deep fascia of the thigh (fascia lata). B. Note the attachment of the membranous layer to the posterior margin of the perineal membrane. Arrows indicate paths taken by urine in cases of ruptured urethra.

Veins The venous drainage passes above mainly into the axillary vein via the lateral thoracic vein and below into the femoral vein via the superficial epigastric and the great saphenous veins (see Fig. 4-18). Superficial Fascia The superficial fascia is divided into a superficial fatty layer (fascia of Camper) and a deep membranous layer (Scarpa’s fascia) (Fig. 4-1). The fatty layer is continuous with the superficial fat over the rest of the body and may be extremely thick (3 in. [8 cm] or more in obese patients). The membranous layer is thin and fades out laterally and above, P.148
where it becomes continuous with the superficial fascia of the back and the thorax, respectively. Inferiorly, the membranous layer passes onto the front of the thigh, where it fuses with the deep fascia one fingerbreadth below the inguinal ligament. In the midline inferiorly, the membranous layer of fascia is not attached to the pubis but forms a tubular sheath for the penis (or clitoris). Below in the perineum, it enters the wall of the scrotum (or labia majora). From there it passes to be attached on each side to the margins of the pubic arch; it is here referred to as Colles’ fascia. Posteriorly, it fuses with the perineal body and the posterior margin of the perineal membrane (Fig. 4-1B).

Figure 4-2 External oblique, internal oblique, and transversus muscles of the anterior abdominal wall.

In the scrotum, the fatty layer of the superficial fascia is represented as a thin layer of smooth muscle, the dartos muscle. The membranous layer of the superficial fascia persists as a separate layer. P.149

Figure 4-3 Anterior view of the rectus abdominis muscle and the rectus sheath. Left: The anterior wall of the sheath has been partly removed, revealing the rectus muscle with its tendinous intersections. Right: The posterior wall of the rectus sheath is shown. The edge of the arcuate line is shown at the level of the anterior superior iliac spine.

Clinical Notes Membranous Layer of Superficial Fascia and the Extravasation of Urine The membranous layer of the superficial fascia is important clinically because beneath it is a potential closed space that does not open into the thigh but is continuous with the superficial perineal pouch via the penis and scrotum. Rupture of the penile urethra may be followed by extravasation of urine into the scrotum, perineum, and penis and then up into the lower part of the anterior abdominal wall deep to the membranous layer of fascia. The urine is excluded from the thigh because of the attachment of the fascia to the fascia lata (Fig. 4-1). When closing abdominal wounds it is usual for a surgeon to put in a continuous suture uniting the divided membranous layer of superficial fascia. This strengthens the healing wound, prevents stretching of the skin scar, and makes for a more cosmetically acceptable result. Deep Fascia The deep fascia in the anterior abdominal wall is merely a thin layer of connective tissue covering the muscles; it lies immediately deep to the membranous layer of superficial fascia. Muscles of the Anterior Abdominal Wall The muscles of the anterior abdominal wall consist of three broad thin sheets that are aponeurotic in front; from exterior to interior they are the external oblique, internal oblique, and transversus (Fig. 4-2). On either side of the midline anteriorly is, in addition, a wide vertical muscle, the rectus abdominis (Fig. 4-3). As the aponeuroses of the three sheets pass forward, they enclose the rectus abdominis to form the rectus sheath. The lower part of the rectus sheath might contain a small muscle called the pyramidalis. Clinical Notes General Appearances of the Abdominal Wall The normal abdominal wall is soft and pliable and undergoes inward and outward excursion with respiration. The contour is subject to considerable variation and depends on the tone of its muscles and the amount of fat in the subcutaneous tissue. Well-developed muscles or an abundance of fat can prove to be a severe obstacle to the palpation of the abdominal viscera. P.150
External Oblique The external oblique muscle is a broad, thin, muscular sheet that arises from the outer surfaces of the lower eight ribs and fans out to be inserted into the xiphoid process, the linea alba, the pubic crest, the pubic tubercle, and the anterior half of the iliac crest (Fig. 4-2). Most of the fibers are inserted by means of a broad aponeurosis. Note that the most posterior fibers passing down to the iliac crest form a posterior free border. A triangular-shaped defect in the external oblique aponeurosis lies immediately above and medial to the pubic tubercle. This is known as the superficial inguinal ring (Figs. 4-2 and 4-3). The spermatic cord (or round ligament of the uterus) passes through this opening and carries the external spermatic fascia (or the external covering of the round ligament of the uterus) from the margins of the ring (Figs. 4-4 and 4-5).

Figure 4-4 A. Continuity of the different layers of the anterior abdominal wall with coverings of the spermatic cord. B. The skin and superficial fascia of the abdominal wall and scrotum have been included, and the tunica vaginalis is shown.
Figure 4-5 Scrotum dissected from in front. Note the spermatic cord and its coverings.

Between the anterior superior iliac spine and the pubic tubercle, the lower border of the aponeurosis is folded backward on itself, forming the inguinal ligament (Figs. 4-2 and 4-6). From the medial end of the ligament, the lacunar ligament extends backward and upward to the pectineal line on the superior ramus of the pubis (Fig. 4-6). Its sharp, free crescentic edge forms the medial margin of the femoral ring (see page 579). P.151
P.152
On reaching the pectineal line, the lacunar ligament becomes continuous with a thickening of the periosteum called the pectineal ligament (Fig. 4-6).

Figure 4-6 Bony pelvis viewed from above. Note the attachments of the inguinal, lacunar, and pectineal ligaments.

The lateral part of the posterior edge of the inguinal ligament gives origin to part of the internal oblique and transversus abdominis muscles. To the inferior rounded border of the inguinal ligament is attached the deep fascia of the thigh, the fascia lata (Fig. 4-1). Internal Oblique The internal oblique muscle is also a broad, thin, muscular sheet that lies deep to the external oblique; most of its fibers run at right angles to those of the external oblique (Fig. 4-2). It arises from the lumbar fascia, the anterior two thirds of the iliac crest, and the lateral two thirds of the inguinal ligament. The muscle fibers radiate as they pass upward and forward. The muscle is inserted into the lower borders of the lower three ribs and their costal cartilages, the xiphoid process, the linea alba, and the symphysis pubis. The internal oblique has a lower free border that arches over the spermatic cord (or round ligament of the uterus) and then descends behind it to be attached to the pubic crest and the pectineal line. Near their insertion, the lowest tendinous fibers are joined by similar fibers from the transversus abdominis to form the conjoint tendon (Figs. 4-7 and 4-8). The conjoint tendon is attached medially to the linea alba, but it has a lateral free border. As the spermatic cord (or round ligament of the uterus) passes under the lower border of the internal oblique, it carries with it some of the muscle fibers that are called the cremaster muscle (Figs. 4-7 and 4-8). The cremasteric fascia is the term used to describe the cremaster muscle and its fascia.

Figure 4-7 Anterior view of the pelvis showing the attachment of the conjoint tendon to the pubic crest and the adjoining part of the pectineal line.

Transversus The transversus muscle is a thin sheet of muscle that lies deep to the internal oblique, and its fibers run horizontally forward (Fig. 4-2). It arises from the deep surface of the lower six costal cartilages (interdigitating with the diaphragm), the lumbar fascia, the anterior two thirds of the iliac crest, and the lateral third of the inguinal ligament. It is inserted into the xiphoid process, the linea alba, and the symphysis pubis. The lowest tendinous fibers join similar fibers from the internal oblique to form the conjoint tendon, which is fixed to the pubic crest and the pectineal line (Figs. 4-7 and 4-8). Note that the posterior border of the external oblique muscle is free, whereas the posterior borders of the internal oblique and transversus muscles are attached to the lumbar vertebrae by the lumbar fascia (Figs. 4-2 and 4-9). Rectus Abdominis The rectus abdominis is a long strap muscle that extends along the whole length of the anterior abdominal wall. It is broader above and lies close to the midline, being separated from its fellow by the linea alba.

Figure 4-8 Inguinal canal showing the arrangement of the external oblique muscle (A), the internal oblique muscle (B), the transversus muscle (C), and the fascia transversalis (D). Note that the anterior wall of the canal is formed by the external oblique and the internal oblique and the posterior wall is formed by the fascia transversalis and the conjoint tendon. The deep inguinal ring lies lateral to the inferior epigastric artery.
Figure 4-9 Cross section of the abdomen showing the courses of the lower thoracic and first lumbar nerves.

The rectus abdominis muscle arises by two heads, from the front of the symphysis pubis and from the pubic crest (Figs. 4-6 and 4-10). It is inserted into the fifth, sixth, and seventh costal cartilages and the xiphoid process (Fig. 4-3). When it contracts, its lateral margin forms a curved ridge that can be palpated and often seen and is termed the linea semilunaris (Figs. 4-3, 4-11, and 4-12). This extends from the tip of the ninth costal cartilage to the pubic tubercle. P.153
P.154
The rectus abdominis muscle is divided into distinct segments by three transverse tendinous intersections: one at the level of the xiphoid process, one at the level of the umbilicus, and one halfway between these two (Fig. 4-3). These intersections are strongly attached to the anterior wall of the rectus sheath (see below). The rectus abdominis is enclosed between the aponeuroses of the external oblique, internal oblique, and transversus, which form the rectus sheath. Pyramidalis The pyramidalis muscle is often absent. It arises by its base from the anterior surface of the pubis and is inserted into the linea alba (Fig. 4-3). It lies in front of the lower part of the rectus abdominis. Rectus Sheath The rectus sheath is a long fibrous sheath that encloses the rectus abdominis muscle and pyramidalis muscle (if present) and contains the anterior rami of the lower six thoracic nerves and the superior and inferior epigastric vessels and lymph vessels. It is formed mainly by the aponeuroses of the three lateral abdominal muscles (Figs. 4-2, 4-3, and 4-10). For ease of description the rectus sheath is considered at three levels (Fig. 4-13).

  • Above the costal margin, the anterior wall is formed by the aponeurosis of the external oblique. The posterior wall is formed by the thoracic wall—that is, the fifth, sixth, and seventh costal cartilages and the intercostal spaces.
  • Between the costal margin and the level of the anterior superior iliac spine, the aponeurosis of the internal oblique splits to enclose the rectus muscle; the external oblique aponeurosis is directed in front of the muscle, and the transversus aponeurosis is directed behind the muscle.
  • Between the level of the anterosuperior iliac spine and the pubis, the aponeuroses of all three muscles form the anterior wall. The posterior wall is absent, and the rectus muscle lies in contact with the fascia transversalis.

It should be noted that where the aponeuroses forming the posterior wall pass in front of the rectus at the level of the anterior superior iliac spine, the posterior wall has a free, curved lower border called the arcuate line (Figs. 4-3 and 4-10). At this site, the inferior epigastric vessels enter the P.155
P.156
rectus sheath and pass upward to anastomose with the superior epigastric vessels.

Figure 4-10 Rectus sheath in anterior view (A) and in sagittal section (B). Note the arrangement of the aponeuroses forming the rectus sheath.
Figure 4-11 Anterior abdominal wall of a 27-year-old man.
Figure 4-12 Surface landmarks and regions of the anterior abdominal wall.

The rectus sheath is separated from its fellow on the opposite side by a fibrous band called the linea alba (Figs. 4-3, 4-7, and 4-13). This extends from the xiphoid process down to the symphysis pubis and is formed by the fusion of the aponeuroses of the lateral muscles of the two sides. Wider above the umbilicus, it narrows down below the umbilicus to be attached to the symphysis pubis. The posterior wall of the rectus sheath is not attached to the rectus abdominis muscle. The anterior wall is firmly attached to it by the muscle’s tendinous intersections (Figs. 4-3 and 4-10). Clinical Notes Hematoma of the Rectus Sheath Hematoma of the rectus sheath is uncommon but important, since it is often overlooked. It occurs most often on the right side below the level of the umbilicus. The source of the bleeding is the inferior epigastric vein or, more rarely, the inferior epigastric artery. These vessels may be stretched during a severe bout of coughing or in the later months of pregnancy, which may predispose to the condition. The cause is usually blunt trauma to the abdominal wall, such as a fall or a kick. The symptoms that follow the trauma include midline abdominal pain. An acutely tender mass confined to one rectus sheath is diagnostic. P.157

Figure 4-13 Transverse sections of the rectus sheath seen at three levels. A. Above the costal margin. B. Between the costal margin and the level of the anterior superior iliac spine. C. Below the level of the anterior superior iliac spine and above the pubis.

Function of the Anterior Abdominal Wall Muscles The oblique muscles laterally flex and rotate the trunk (Fig. 4-14). The rectus abdominis flexes the trunk and stabilizes the pelvis, and the pyramidalis keeps the linea alba taut during the process.

Figure 4-14 Action of the muscles of the anterior and lateral abdominal walls. Arrows indicate line of pull of different muscles.

The muscles of the anterior and lateral abdominal walls assist the diaphragm during inspiration by relaxing as the diaphragm descends so that the abdominal viscera can be accommodated. The muscles assist in the act of forced expiration that occurs during coughing and sneezing by pulling down the ribs and sternum. Their tone plays an important part in supporting and protecting the abdominal viscera. By contracting simultaneously with the diaphragm, with the glottis of the larynx closed, they increase the intra-abdominal pressure and help in micturition, defecation, vomiting, and parturition. Nerve Supply of Anterior Abdominal Wall Muscles The oblique and transversus abdominis muscles are supplied by the lower six thoracic nerves and the iliohypogastric and ilioinguinal nerves (L1). The rectus muscle is supplied by the lower six thoracic nerves (Figs. 4-9 and 4-15). The pyramidalis is supplied by the 12th thoracic nerve. A summary of the muscles of the anterior abdominal wall, their nerve supply, and their action is given in Table 4-1. Fascia Transversalis The fascia transversalis is a thin layer of fascia that lines the transversus abdominis muscle and is continuous with a similar layer lining the diaphragm and the iliacus muscle (Fig. 4-10). The femoral sheath for the femoral vessels in the lower limbs is formed from the fascia transversalis and the fascia iliaca that covers the iliacus muscle (see page 579). P.158

Figure 4-15 Segmental innervation of the anterior abdominal wall (left) and arterial supply to the anterior abdominal wall (right).
Table 4-1 Muscles of the Anterior Abdominal Wall
Name of Muscle Origin Insertion Nerve Supply Action
External oblique Lower eight ribs Xiphoid process, linea alba, pubic crest, pubic tubercle, iliac crest Lower six thoracic nerves and iliohypogastric and ilioinguinal nerves (L1) Supports abdominal contents; compresses abdominalcontents; assists in flexing and rotation of trunk; assists inforced expiration, micturition, defecation, parturition, and vomiting
Internal oblique Lumbar fascia, iliac crest, lateral two thirds of inguinal ligament Lower three ribs and costal cartilages, xiphoid process, linea alba, symphysis pubis Lower six thoracic nerves and iliohypogastric and ilioinguinal nerves (L1) As above
Transversus Lower six costal cartilages, lumbar fascia, iliac crest, lateral third of inguinal ligament Xiphoid process linea alba, symphysis pubis Lower six thoracic nerves and iliohypogastric and ilioinguinal nerves (L1) Compresses abdominal contents
Rectus abdominis Symphysis pubis and pubic crest Fifth, sixth, and seventh costal cartilages and xiphoid process Lower six thoracic nerves Compresses abdominal contents and flexes vertebral column; accessory muscle of expiration
Pyramidalis (if present) Anterior surface of pubis Linea alba 12th thoracic nerve Tenses the linea alba

Clinical Notes Abdominal Muscles, Abdominothoracic Rhythm, and Visceroptosis The abdominal muscles contract and relax with respiration, and the abdominal wall conforms to the volume of the abdominal viscera. There is an abdominothoracic rhythm. Normally, during inspiration, when the sternum moves forward and the chest expands, the anterior abdominal wall also moves forward. If, when the chest expands, the anterior abdominal wall remains stationary or contracts inward, it is highly probable that the parietal peritoneum is inflamed and has caused a reflex contraction of the abdominal muscles. The shape of the anterior abdominal wall depends on the tone of its muscles. A middle-aged woman with poor abdominal muscles who has had multiple pregnancies is often incapable of supporting her abdominal viscera. The lower part of the anterior abdominal wall protrudes forward, a condition known as visceroptosis. This should not be confused with an abdominal tumor such as an ovarian cyst or with the excessive accumulation of fat in the fatty layer of the superficial fascia. P.159
Extraperitoneal Fat The extraperitoneal fat is a thin layer of connective tissue that contains a variable amount of fat and lies between the fascia transversalis and the parietal peritoneum (Fig. 4-10). Parietal Peritoneum The walls of the abdomen are lined with parietal peritoneum (Fig. 4-10). This is a thin serous membrane and is continuous below with the parietal peritoneum lining the pelvis (see pages 359 and 376). Clinical Notes Abdominal Pain See also page 280. Muscle Rigidity and Referred Pain Sometimes it is difficult for a physician to decide whether the muscles of the anterior abdominal wall of a patient are rigid because of underlying inflammation of the parietal peritoneum or whether the patient is voluntarily contracting the muscles because he or she resents being examined or because the physician’s hand is cold. This problem is usually easily solved by asking the patient, who is lying supine on the examination table, to rest the arms by the sides and draw up the knees to flex the hip joints. It is practically impossible for a patient to keep the abdominal musculature tensed when the thighs are flexed. Needless to say, the examiner’s hand should be warm. A pleurisy involving the lower costal parietal pleura causes pain in the overlying skin that may radiate down into the abdomen. Although it is unlikely to cause rigidity of the abdominal muscles, it may cause confusion in making a diagnosis unless these anatomic facts are remembered. It is useful to remember the following: Dermatomes over:

  • The xiphoid process: T7
  • The umbilicus: T10
  • The pubis: L1

Anterior Abdominal Nerve Block Area of Anesthesia The area of anesthesia is the skin of the anterior abdominal wall. The nerves of the anterior and lateral abdominal walls are the anterior rami of the 7th through the 12th thoracic nerves and the first lumbar nerve (ilioinguinal and iliohypogastric nerves). Indications An anterior abdominal nerve block is performed to repair lacerations of the anterior abdominal wall.

Figure 4-16 Dermatomes and distribution of cutaneous nerves on the anterior abdominal wall.

Procedure The anterior ends of intercostal nerves T7 through T11 enter the abdominal wall by passing posterior to the costal cartilages (Fig. 4-17). An abdominal field block is most easily carried out along the lower border of the costal margin and then infiltrating the nerves as they emerge between the xiphoid process and the 10th or 11th rib along the costal margin. The ilioinguinal nerve passes forward in the inguinal canal and emerges through the superficial inguinal ring. The iliohypogastric nerve passes forward around the abdominal wall and pierces the external oblique aponeurosis above the superficial inguinal ring. The two nerves are easily blocked by inserting the anesthetic needle 1 in. (2.5 cm) above the anterior superior iliac spine on the spinoumbilical line (Fig. 4-17). Nerves of the Anterior Abdominal Wall The nerves of the anterior abdominal wall are the anterior rami of the lower six thoracic and the first lumbar nerves (Figs. 4-9, 4-15, and 4-16). They pass forward in the interval between the internal oblique and the transversus muscles. The thoracic nerves are the lower five intercostal nerves and the subcostal nerves, and the first lumbar nerve is represented by the iliohypogastric and ilioinguinal nerves, branches of the lumbar plexus. They supply the skin of the anterior abdominal wall, the muscles, and the parietal peritoneum. (Compare with the intercostal nerves, which run forward in the intercostal spaces between the internal intercostal and the innermost intercostal muscles; see page 55). The lower six thoracic nerves pierce the posterior wall of the rectus sheath to supply the rectus muscle and the pyramidalis (T12 only). They terminate by piercing the anterior wall of the sheath and supplying the skin. The first lumbar nerve has a similar course, but it does not enter the rectus sheath (Figs. 4-9, 4-15, and 4-16). It is represented by the iliohypogastric nerve, which pierces the external oblique aponeurosis above the superficial inguinal ring, and by the ilioinguinal nerve, which emerges through the ring. They end by supplying the skin just above the inguinal ligament and symphysis pubis. The dermatome of T7 is located in the epigastrium over the xiphoid process, that of T10 includes the umbilicus, and that of L1 lies just above the inguinal ligament and the symphysis pubis. For the dermatomes of the anterior abdominal wall, see Figure 4-16. P.160

Figure 4-17 Anterior abdominal wall nerve blocks. T7 though T11 are blocked (X) as they emerge from beneath the costal margin. The iliohypogastric ilioinguinal nerves are blocked by inserting the needle about 1 in. (2.5 cm) above the anterior superior iliac spine on the spinoumbilical line (X). The terminal branches of the genitofemoral nerve are blocked by inserting the needle through the skin just lateral to the pubic tubercle and infiltrating the subcutaneous tissue with anesthetic solution (X).

P.161
Arteries of the Anterior Abdominal Wall The superior epigastric artery, one of the terminal branches of the internal thoracic artery, enters the upper part of the rectus sheath between the sternal and costal origins of the diaphragm (Fig. 4-15). It descends behind the rectus muscle, supplying the upper central part of the anterior abdominal wall, and anastomoses with the inferior epigastric artery. The inferior epigastric artery is a branch of the external iliac artery just above the inguinal ligament. It runs upward and medially along the medial side of the deep inguinal ring (Figs. 4-4, 4-8, and 4-15). It pierces the fascia transversalis to enter the rectus sheath anterior to the arcuate line (Fig. 4-10). It ascends behind the rectus muscle, supplying the lower central part of the anterior abdominal wall, and anastomoses with the superior epigastric artery. The deep circumflex iliac artery is a branch of the external iliac artery just above the inguinal ligament (Fig. 4-15). It runs upward and laterally toward the anterosuperior iliac spine and then continues along the iliac crest. It supplies the lower lateral part of the abdominal wall. The lower two posterior intercostal arteries, branches of the descending thoracic aorta, and the four lumbar arteries, branches of the abdominal aorta, pass forward between the muscle layers and supply the lateral part of the abdominal wall (Fig. 4-15). P.162

Figure 4-18 Superficial veins of the anterior abdominal wall. On the left are anastomoses between systemic veins and the portal vein via paraumbilical veins. Arrows indicate the direction taken by venous blood when the portal vein is obstructed. On the right is an enlarged anastomosis between the lateral thoracic vein and the superficial epigastric vein. This occurs if either the superior or the interior vena cava is obstructed.

Veins of the Anterior Abdominal Wall Superficial Veins The superficial veins form a network that radiates out from the umbilicus (Fig. 4-18). Above, the network is drained into the axillary vein via the lateral thoracic vein and, below, into the femoral vein via the superficial epigastric and great saphenous veins. A few small veins, the paraumbilical veins, connect the network through the umbilicus and along the ligamentum teres to the portal vein. This forms an important portal–systemic venous anastomosis. Clinical Notes Portal Vein Obstruction In cases of portal vein obstruction (Fig. 4-19), the superficial veins around the umbilicus and the paraumbilical veins become grossly distended. The distended subcutaneous veins radiate out from the umbilicus, producing in severe cases the clinical picture referred to as caput medusae. Deep Veins The deep veins of the abdominal wall, the superior epigastric, inferior epigastric, and deep circumflex iliac veins, follow the arteries of the same name and drain into the internal thoracic and external iliac veins. The posterior intercostal veins drain into the azygos veins, and the lumbar veins drain into the inferior vena cava. Clinical Notes Caval Obstruction If the superior or inferior vena cava is obstructed, the venous blood causes distention of the veins running from the anterior chest wall to the thigh. The lateral thoracic vein anastomoses with the superficial epigastric vein, a tributary of the great saphenous vein of the leg. In these circumstances, a tortuous varicose vein may extend from the axilla to the lower abdomen (Fig. 4-18). Lymph Drainage of the Anterior Abdominal Wall Superficial Lymph Vessels The lymph drainage of the skin of the anterior abdominal wall above the level of the umbilicus is upward to the anterior axillary (pectoral) group of nodes, which can be palpated just beneath the lower border of the pectoralis major muscle. Below the level of the umbilicus, the lymph drains downward and laterally to the superficial inguinal nodes (Fig. 4-19). The lymph of the skin of the back above the level of the iliac crests is drained upward to the posterior axillary group of nodes, palpated on the posterior wall of the axilla; below the level of the iliac crests, it drains downward to the superficial inguinal nodes (Fig. 4-19). P.163

Figure 4-19 Lymph drainage of the skin of the anterior and posterior abdominal walls. Also shown is an example of caput medusae in a case of portal obstruction caused by cirrhosis of the liver.

Clinical Notes Skin and Its Regional Lymph Nodes Knowledge of the areas of the skin that drain into a particular group of lymph nodes is clinically important. For example, it is possible to find a swelling in the groin (enlarged superficial inguinal node) caused by an infection or malignant tumor of the skin of the lower part of the anterior abdominal wall or that of the buttock. Deep Lymph Vessels The deep lymph vessels follow the arteries and drain into the internal thoracic, external iliac, posterior mediastinal, and para-aortic (lumbar) nodes. Inguinal Canal The inguinal canal is an oblique passage through the lower part of the anterior abdominal wall. In the males, it allows structures to pass to and from the testis to the abdomen. In P.164
females it allows the round ligament of the uterus to pass from the uterus to the labium majus. The canal is about 1.5 in. (4 cm) long in the adult and extends from the deep inguinal ring, a hole in the fascia transversalis (see page 177), downward and medially to the superficial inguinal ring, a hole in the aponeurosis of the external oblique muscle (Figs. 4-3 and 4-8). It lies parallel to and immediately above the inguinal ligament. In the newborn child, the deep ring lies almost directly posterior to the superficial ring so that the canal is considerably shorter at this age. Later, as the result of growth, the deep ring moves laterally. The deep inguinal ring,* an oval opening in the fascia transversalis, lies about 0.5 in. (1.3 cm) above the inguinal ligament midway between the anterior superior iliac spine and the symphysis pubis (Figs. 4-4 and 4-8). Related to it medially are the inferior epigastric vessels, which pass upward from the external iliac vessels. The margins of the ring give attachment to the internal spermatic fascia (or the internal covering of the round ligament of the uterus). The superficial inguinal ring* is a triangular-shaped defect in the aponeurosis of the external oblique muscle and lies immediately above and medial to the pubic tubercle (Figs. 4-3, 4-5, and 4-8). The margins of the ring, sometimes called the crura, give attachment to the external spermatic fascia. Walls of the Inguinal Canal

  • Anterior wall: External oblique aponeurosis, reinforced laterally by the origin of the internal oblique from the inguinal ligament (Figs. 4-3 and 4-8). This wall is therefore strongest where it lies opposite the weakest part of the posterior wall, namely, the deep inguinal ring.
  • Posterior wall: Conjoint tendon medially, fascia transversalis laterally (Figs. 4-4 and 4-8). This wall is therefore strongest where it lies opposite the weakest part of the anterior wall, namely, the superficial inguinal ring.
  • Roof or superior wall: Arching lowest fibers of the internal oblique and transversus abdominis muscles (Fig. 4-7)
  • Floor or inferior wall: Upturned lower edge of the inguinal ligament and, at its medial end, the lacunar ligament (Fig. 4-7).

Function of the Inguinal Canal The inguinal canal allows structures of the spermatic cord to pass to and from the testis to the abdomen in the male. (Normal spermatogenesis takes place only if the testis leaves the abdominal cavity to enter a cooler environment in the scrotum.) In the female, the smaller canal permits the passage of the round ligament of the uterus from the uterus to the labium majus. Mechanics of the Inguinal Canal The inguinal canal in the lower part of the anterior abdominal wall is a site of potential weakness in both sexes. It is interesting to consider how the design of this canal attempts to lessen this weakness.

  • Except in the newborn infant, the canal is an oblique passage with the weakest areas, namely, the superficial and deep rings, lying some distance apart.
  • The anterior wall of the canal is reinforced by the fibers of the internal oblique muscle immediately in front of the deep ring.
  • The posterior wall of the canal is reinforced by the strong conjoint tendon immediately behind the superficial ring.
  • On coughing and straining, as in micturition, defecation, and parturition, the arching lowest fibers of the internal oblique and transversus abdominis muscles contract, flattening out the arched roof so that it is lowered toward the floor. The roof may actually compress the contents of the canal against the floor so that the canal is virtually closed (Fig. 4-20).
  • When great straining efforts may be necessary, as in defecation and parturition, the person naturally tends to assume the squatting position; the hip joints are flexed, and the anterior surfaces of the thighs are brought up against the anterior abdominal wall. By this means, the lower part of the anterior abdominal wall is protected by the thighs (Fig. 4-20).

Spermatic Cord The spermatic cord is a collection of structures that pass through the inguinal canal to and from the testis (Fig. 4-21). It begins at the deep inguinal ring lateral to the inferior epigastric artery and ends at the testis. Structures of the Spermatic Cord The structures are as follows:

  • Vas deferens
  • Testicular artery
  • Testicular veins (pampiniform plexus)
  • Testicular lymph vessels
  • Autonomic nerves
  • Remains of the processus vaginalis
  • Genital branch of the genitofemoral nerve, which supplies the cremaster muscle

Vas Deferens (Ductus Deferens) The vas deferens is a cordlike structure (Figs. 4-5 and 4-21) that can be palpated between finger and thumb in the upper part of the scrotum. It is a thick-walled muscular duct that transports spermatozoa from the epididymis to the urethra. Testicular Artery A branch of the abdominal aorta (at the level of the second lumbar vertebra), the testicular artery is long and slender and descends on the posterior abdominal wall. It traverses the inguinal canal and supplies the testis and the epididymis (Fig. 4-21). P.165

Figure 4-20 Action of the muscles on the inguinal canal. Note that the canal is “obliterated” when the muscles contract. Note also that the anterior surface of the thigh protects the inguinal region when one assumes the squatting position.

Testicular Veins An extensive venous plexus, the pampiniform plexus, leaves the posterior border of the testis (Fig. 4-21). As the plexus ascends, it becomes reduced in size so that at about the level of the deep inguinal ring, a single testicular vein is formed. This runs up on the posterior abdominal wall and drains into the left renal vein on the left side and into the inferior vena cava on the right side. Lymph Vessels The testicular lymph vessels ascend through the inguinal canal and pass up over the posterior abdominal wall to reach the lumbar (para-aortic) lymph nodes on the side of the aorta at the level of the first lumbar vertebra (Fig. 4-22). Autonomic Nerves Sympathetic fibers run with the testicular artery from the renal or aortic sympathetic plexuses. Afferent sensory nerves accompany the efferent sympathetic fibers. Processus Vaginalis The remains of the processus vaginalis are present within the cord (see below). Genital Branch of the Genitofemoral Nerve This nerve supplies the cremaster muscle (Fig. 4-21) (see page 278). Coverings of the Spermatic Cord (the Spermatic Fasciae) The coverings of the spermatic cord are three concentric layers of fascia derived from the layers of the anterior abdominal wall. Each covering is acquired as the processus vaginalis descends into the scrotum through the layers of the abdominal wall (Fig. 4-23).

  • External spermatic fascia derived from the external oblique aponeurosis and attached to the margins of the superficial inguinal ring
  • Cremasteric fascia derived from the internal oblique muscle
  • Internal spermatic fascia derived from the fascia transversalis and attached to the margins of the deep inguinal ring

To understand the coverings of the spermatic cord, one must first consider the development of the inguinal canal. Development of the Inguinal Canal Before the descent of the testis and the ovary from their site of origin high on the posterior abdominal wall (L1), a peritoneal diverticulum called the processus vaginalis is formed (Fig. 4-23). The processus vaginalis passes through the layers of the lower part of the anterior abdominal wall P.166
and, as it does so, acquires a tubular covering from each layer. It traverses the fascia transversalis at the deep inguinal ring and acquires a tubular covering, the internal spermatic fascia (Fig. 4-4). As it passes through the lower part of the internal oblique muscle, it takes with it some of its lowest fibers, which form the cremaster muscle. The muscle fibers are embedded in fascia, and thus the second tubular sheath is known as the cremasteric fascia (Fig. 4-4). The processus vaginalis passes under the arching fibers of the transversus abdominis muscle and therefore does not acquire a covering from this abdominal layer. On reaching the aponeurosis of the external oblique, it evaginates this to form the superficial inguinal ring and acquires a third tubular fascial coat, the external spermatic fascia (Figs. 4-4 and 4-5). It is in this manner that the inguinal canal is formed in both sexes. (In the female the term spermatic fascia should be replaced by the covering of the round ligament of the uterus.)

Figure 4-21 Testis and epididymis, spermatic cord, and scrotum. Also shown is the testis and epididymis cut across in horizontal section.

Meanwhile, a band of mesenchyme, extending from the lower pole of the developing gonad through the inguinal canal to the labioscrotal swelling, has condensed to form the gubernaculum (Fig. 4-23). In the male, the testis descends through the pelvis and inguinal canal during the seventh and eighth months of fetal life. The normal stimulus for the descent of the testis is testosterone, which is secreted by the fetal testes. The testis follows the gubernaculum and descends behind the peritoneum on the posterior abdominal wall. The testis then passes behind the processus vaginalis and pulls down its duct, blood vessels, nerves, and lymph vessels. The testis P.167
takes up its final position in the developing scrotum by the end of the eighth month.

Figure 4-22 Lymph drainage of the testis and the skin of the scrotum.

Because the testis and its accompanying vessels, ducts, and so on follow the course previously taken by the processus vaginalis, they acquire the same three coverings as they pass down the inguinal canal. Thus, the spermatic cord is covered by three concentric layers of fascia: the external spermatic fascia, the cremasteric fascia, and the internal spermatic fascia. In the female, the ovary descends into the pelvis following the gubernaculum (Fig. 4-23). The gubernaculum becomes attached to the side of the developing uterus, and the gonad descends no farther. That part of the gubernaculum extending from the uterus into the developing labium majus persists as the round ligament of the uterus. Thus, in the female, the only structures that pass through the inguinal canal from the abdominal cavity are the round ligament of the uterus and a few lymph vessels. The lymph vessels convey a small amount of lymph from the body of the uterus to the superficial inguinal nodes. Clinical Notes Vasectomy Bilateral vasectomy is a simple operation performed to produce infertility. Under local anesthesia, a small incision is made in the upper part of the scrotal wall, and the vas deferens is divided between ligatures. Spermatozoa may be present in the first few postoperative ejaculations, but that is simply an emptying process. Now only the secretions of the seminal vesicles and prostate constitute the seminal fluid, which can be ejaculated as before. Scrotum, Testis, and Epididymides Scrotum The scrotum is an outpouching of the lower part of the anterior abdominal wall. It contains the testes, the epididymides, and the lower ends of the spermatic cords (Figs. 4-4 and 4-21). The wall of the scrotum has the following layers:

  • Skin: The skin of the scrotum is thin, wrinkled, and pigmented and forms a single pouch. A slightly raised ridge in the midline indicates the line of fusion of the two lateral labioscrotal swellings. (In the female, the swellings remain separate and form the labia majora.)
  • Superficial fascia: This is continuous with the fatty and membranous layers of the anterior abdominal wall; the fat is, however, replaced by smooth muscle called the dartos muscle. This is innervated by sympathetic nerve fibers and is responsible for the wrinkling of the overlying skin. The membranous layer of the superficial fascia (often referred to as Colles’ fascia) is continuous in front with the membranous layer of the anterior abdominal wall (Scarpa’s fascia), and behind it is attached to the perineal body and the posterior edge of the perineal membrane (Fig. 4-1). At the sides it is attached to the ischiopubic rami. Both layers of superficial fascia contribute to a median partition that crosses the scrotum and separates the testes from each other.
  • Spermatic fasciae: These three layers lie beneath the superficial fascia and are derived from the three layers of the anterior abdominal wall on each side, as previously explained. The external spermatic fascia is derived from the aponeurosis of the external oblique muscle; the cremasteric fascia is derived from the internal oblique muscle; and, finally, the internal spermatic fascia is derived from the fascia transversalis. The cremaster muscle is P.168
    supplied by the genital branch of the genitofemoral nerve (see page 279). The cremaster muscle can be made to contract by stroking the skin on the medial aspect of the thigh. This is called the cremasteric reflex. The afferent fibers of this reflex arc travel in the femoral branch of the genitofemoral nerve (L1 and 2), and the efferent motor nerve fibers travel in the genital branch of the genitofemoral nerve. The function of the cremaster muscle is to raise the testis and the scrotum upward for warmth and for protection against injury. For testicular temperature and fertility, see page 169.
    Figure 4-23 Origin, development, and fate of the processus vaginalis in the two sexes. Note the descent of the testis into the scrotum and the descent of the ovary into the pelvis.
  • Tunica vaginalis (Figs. 4-4, 4-5, and 4-21): This lies within the spermatic fasciae and covers the anterior, medial, and lateral surfaces of each testis. It is the lower expanded part of the processus vaginalis; normally, just before birth, it becomes shut off from the upper part of the processus and the peritoneal cavity. The tunica vaginalis is thus a closed sac, invaginated from behind by the testis.

P.169
Lymph Drainage of the Scrotum Lymph from the skin and fascia, including the tunica vaginalis, drains into the superficial inguinal lymph nodes (Fig. 4-22). Testis The testis is a firm, mobile organ lying within the scrotum (Figs. 4-5 and 4-21). The left testis usually lies at a lower level than the right. Each testis is surrounded by a tough fibrous capsule, the tunica albuginea. Extending from the inner surface of the capsule is a series of fibrous septa that divide the interior of the organ into lobules. Lying within each lobule are one to three coiled seminiferous tubules. The tubules open into a network of channels called the rete testis. Small efferent ductules connect the rete testis to the upper end of the epididymis (Fig. 4-21). Normal spermatogenesis can occur only if the testes are at a temperature lower than that of the abdominal cavity. When they are located in the scrotum, they are at a temperature about 3°C lower than the abdominal temperature. The control of testicular temperature in the scrotum is not fully understood, but the surface area of the scrotal skin can be changed reflexly by the contraction of the dartos and cremaster muscles. It is now recognized that the testicular veins in the spermatic cord that form the pampiniform plexus—together with the branches of the testicular arteries, which lie close to the veins—probably assist in stabilizing the temperature of the testes by a countercurrent heat exchange mechanism. By this means, the hot blood arriving in the artery from the abdomen loses heat to the blood ascending to the abdomen within the veins. Epididymis The epididymis is a firm structure lying posterior to the testis, with the vas deferens lying on its medial side (Fig. 4-21). It has an expanded upper end, the head, a body, and a pointed tail inferiorly. Laterally, a distinct groove lies between the testis and the epididymis, which is lined with the inner visceral layer of the tunica vaginalis and is called the sinus of the epididymis (Fig. 4-21). Clinical Notes Clinical Conditions Involving the Scrotum and Testis Varicocele A varicocele is a condition in which the veins of the pampiniform plexus are elongated and dilated. It is a common disorder in adolescents and young adults, with most occurring on the left side. This is thought to be because the right testicular vein joins the low-pressure inferior vena cava, whereas the left vein joins the left renal vein, in which the venous pressure is higher. Rarely, malignant disease of the left kidney extends along the renal vein and blocks the exit of the testicular vein. A rapidly developing left-sided variocele should therefore always lead one to examine the left kidney. Malignant Tumor of the Testis A malignant tumor of the testis spreads upward via the lymph vessels to the lumbar (para-aortic) lymph nodes at the level of the first lumbar vertebra. It is only later, when the tumor spreads locally to involve the tissues and skin of the scrotum, that the superficial inguinal lymph nodes are involved. The process of the descent of the testis is shown in Figure 4-23. The testis may be subject to the following congenital anomalies: Torsion of the Testis Torsion of the testis is a rotation of the testis around the spermatic cord within the scrotum. It is often associated with an excessively large tunica vaginalis. Torsion commonly occurs in active young men and children and is accompanied by severe pain. If not treated quickly, the testicular artery may be occluded, followed by necrosis of the testis. Processus Vaginalis The formation of the processus vaginalis and its passage through the lower part of the anterior abdominal wall with the formation of the inguinal canal in both sexes were described elsewhere (see page 165). Normally, the upper part becomes obliterated just before birth and the lower part remains as the tunica vaginalis. The processus is subject to the following common congenital anomalies:

  • It may persist partially or in its entirety as a preformed hernial sac for an indirect inguinal hernia (Fig. 4-24).
  • It may become very much narrowed, but its lumen remains in communication with the abdominal cavity. Peritoneal fluid accumulates in it, forming a congenital hydrocele (Fig. 4-24).
  • The upper and lower ends of the processus may become obliterated, leaving a small intermediate cystic area referred to as an encysted hydrocele of the cord (Fig. 4-24).

The tunica vaginalis is closely related to the front and sides of the testis. It is therefore not surprising to find that inflammation of the testis can cause an accumulation of fluid within the tunica vaginalis. This is referred to simply as a hydrocele (Fig. 4-25). Most hydroceles are idiopathic. To remove excess fluid from the tunica vaginalis, a procedure termed tapping a hydrocele, a fine trocar and cannula are inserted through the scrotal skin (Fig. 4-25). The following anatomic structures are traversed by the cannula: skin, dartos muscle and membranous layer of fascia (Colles’ fascia), external spermatic fascia, cremasteric fascia, internal spermatic fascia, and parietal layer of the tunica vaginalis. The epididymis is a much coiled tube nearly 20 ft (6 m) long, embedded in connective tissue. The tube emerges from the tail of the epididymis as the vas deferens, which enters the spermatic cord. The long length of the duct of the epididymis provides storage space for the spermatozoa and allows them to mature. A main function of the epididymis is the absorption of fluid. Another function may be the addition of substances to the seminal fluid to nourish the maturing sperm. Blood Supply of the Testis and Epididymis The testicular artery is a branch of the abdominal aorta. The testicular veins emerge from the testis and the epididymis as a venous network, the pampiniform plexus. This becomes reduced to a single vein as it ascends through the inguinal canal. The right testicular vein drains into the inferior vena cava, and the left vein joins the left renal vein. Lymph Drainage of the Testis and Epididymis The lymph vessels (Fig. 4-22) ascend in the spermatic cord and end in the lymph nodes on the side of the aorta (lumbar or para-aortic) nodes at the level of the first lumbar vertebra (i.e., on the transpyloric plane). This is to be expected because during development the testis has migrated from high up on the posterior abdominal wall, down through the inguinal canal, and into the scrotum, dragging its blood supply and lymph vessels after it. P.170

Figure 4-24 Common congenital anomalies of the processus vaginalis. A. Congenital hydrocele. B. Encysted hydrocele of the cord. C. Preformed hernial sac for indirect inguinal hernia.

P.171

Figure 4-25 The tunica vaginalis distended with fluid (hydrocele). Also shown are the various anatomic layers traversed by a trocar and cannula when a hydrocele is tapped.

Embryologic Notes Development of the Testis The male sex chromosome causes the genital ridge to secrete testosterone and induces the development of the testis and the other internal and external organs of reproduction. The sex cords of the genital ridge become separated from the coelomic epithelium by the proliferation of the mesenchyme (Fig. 4-26). The outer part of the mesenchyme condenses to form a dense fibrous layer, the tunica albuginea. The sex cords become U-shaped and form the seminiferous tubules. The free ends of the tubules form the straight tubules, which join one another in the mediastinum testis to become the rete testis. The primordial sex cells in the seminiferous tubules form the spermatogonia, and the sex cord cells form the Sertoli cells. The mesenchyme in the developing gonad makes up the connective tissue and fibrous septa. The interstitial cells, which are already secreting testosterone, are also formed of mesenchyme. The rete testis becomes canalized, and the tubules extend into the mesonephric tissue, where they join the remnants of the mesonephric tubules; the latter tubules become the efferent ductules of the testis. The duct of the epididymis, the vas deferens, the seminal vesicle, and the ejaculatory duct are formed from the mesonephric duct (Fig. 4-26). Descent of the Testis The testis develops high up on the posterior abdominal wall, and in late fetal life it “descends” behind the peritoneum, dragging its blood supply, nerve supply, and lymphatic drainage after it (for details, see pages 166). The process of the descent of the testis is shown in Figure 4-23. Congenital Anomalies of the Testis The testis may be subject to the following congenital anomalies.

  • Anterior inversion, in which the epididymis lies anteriorly and the testis and the tunica vaginalis lie posteriorly
  • Polar inversion, in which the testis and epididymis are completely inverted
  • Imperfect descent (cryptorchidism): Incomplete descent (Fig. 4-27), in which the testis, although traveling down its normal path, fails to reach the floor of the scrotum. It may be found within the abdomen, within the inguinal canal, at the superficial inguinal ring, or high up in the scrotum. Maldescent (Fig. 4-28), in which the testis travels down an abnormal path and fails to reach the scrotum. It may be found in the superficial fascia of the anterior abdominal wall above the inguinal ligament, in front of the pubis, in the perineum, or in the thigh.

It is necessary for the testes to leave the abdominal cavity because the temperature there retards the normal process of spermatogenesis. If an incompletely descended testis is brought down into the scrotum by surgery before puberty, it will develop and function normally. A maldescended testis, although often developing normally, is susceptible to traumatic injury and, for this reason, should be placed in the scrotum. Many authorities believe that the incidence of tumor formation is greater in testes that have not descended into the scrotum. The appendix of the testis and the appendix of the epididymis are embryologic remnants found at the upper poles of these organs that may become cystic. The appendix of the testis is derived from the paramesonephric ducts, and the appendix of the epididymis is a remnant of the mesonephric tubules. P.172

Figure 4-26 The formation of the testis and the ducts of the testis.
Figure 4-27 Four degrees of incomplete descent of the testis. 1. In the abdominal cavity close to the deep inguinal ring. 2. In the inguinal canal. 3. At the superficial inguinal ring. 4. In the upper part of scrotum.

P.173
Labia Majora The labia majora are prominent, hair-bearing folds of skin formed by the enlargement of the genital swellings in the fetus. (In the male, the genital swellings fuse in the midline to form the scrotum.) Within the labia are a large amount of adipose tissue and the terminal strands of the round ligaments of the uterus. (For further details see page 367.)

Figure 4-28 Four types of maldescent of the testis. 1. In the superficial fascia of the anterior abdominal wall, above the superficial inguinal ring. 2. At the root of the penis. 3. In the perineum. 4. In the thigh.

Structure of the Posterior Abdominal Wall The posterior abdominal wall is formed in the midline by the five lumbar vertebrae and their intervertebral discs and laterally by the 12th ribs, the upper part of the bony pelvis (Fig. 4-29), the psoas muscles, the quadratus lumborum muscles, and the aponeuroses of origin of the transversus abdominis muscles. The iliacus muscles lie in the upper part of the bony pelvis. Lumbar Vertebrae The body of each vertebra (Fig. 4-30) is massive and kidney shaped, and it has to bear the greater part of the body weight. The fifth lumbar vertebra articulates with the base of the sacrum at the lumbosacral joint. The intervertebral discs (Fig. 4-31) in the lumbar region are thicker than in other regions of the vertebral column. They are wedge shaped and are responsible for the normal posterior concavity in the curvature of the vertebral column in the lumbar region (lordosis). For a full description of the structure of the lumbar vertebrae and the intervertebral discs, see pages 855 and 858. Twelfth Pair of Ribs The ribs are described on page 47. It should be noted that the head of the 12th rib has a single facet for articulation with the body of the 12th thoracic vertebra. The anterior end is pointed and has a small costal cartilage, which is embedded in the musculature of the anterior abdominal wall. In many people it is so short that it fails to protrude beyond the lateral border of the erector spinae muscle on the back. Ilium The ilium, together with the ischium and pubis, forms the hip bone (Fig. 4-32); they meet one another at the acetabulum. The medial surface of the ilium is divided into two parts P.174
by the arcuate line. Above this line is a concave surface called the iliac fossa; below this line is a flattened surface that is continuous with the medial surfaces of the pubis and ischium. It should be noted that the arcuate line of the ilium forms the posterior part of the iliopectineal line, and the pectineal line forms the anterior part of the iliopectineal line. The iliopectineal line runs forward and demarcates the false from the true pelvis. For further details on the structure of the hip bone, see page 316.

Figure 4-29 Costal margin and bones of the abdomen.
Figure 4-30 Fifth lumbar vertebra.

Muscles of the Posterior Abdominal Wall Psoas Major The psoas muscle* arises from the roots of the transverse processes, the sides of the vertebral bodies, and the intervertebral discs, from the 12th thoracic to the 5th lumbar vertebrae (Fig. 4-33). The fibers run downward and laterally and leave the abdomen to enter the thigh by passing behind the inguinal ligament. The muscle is inserted into the lesser trochanter of the femur. The psoas is enclosed in a fibrous sheath that is derived from the lumbar fascia. The sheath is thickened above to form the medial arcuate ligament.

  • Nerve supply: This muscle is supplied by the lumbar plexus.
  • Action: The psoas flexes the thigh at the hip joint on the trunk, or if the thigh is fixed, it flexes the trunk on the thigh, as in sitting up from a lying position.

P.175

Figure 4-31 Sagittal section of the lumbar part of the vertebral column showing intervertebral discs and ligaments.

Clinical Notes Psoas Fascia and Tuberculosis The psoas fascia covers the anterior surface of the psoas muscle and can influence the direction taken by a tuberculous abscess. Tuberculous disease of the thoracolumbar region of the vertebral column results in the destruction of the vertebral bodies, with possible extension of pus laterally under the psoas fascia (Fig. 4-34). From there, the pus tracks downward, following the course of the psoas muscle, and appears as a swelling in the upper part of the thigh below the inguinal ligament. It may be mistaken for a femoral hernia.

Figure 4-32 Internal aspect of the right hip bone.

Quadratus Lumborum The quadratus lumborum is a flat, quadrilateral-shaped muscle that lies alongside the vertebral column. It arises below from the iliolumbar ligament, the adjoining part of the iliac crest, and the tips of the transverse processes of the lower lumbar vertebrae (Fig. 4-33). The fibers run upward and medially and are inserted into the lower border of the 12th rib and the transverse processes of the upper four lumbar vertebrae. The anterior surface of the muscle is covered by lumbar fascia, which is thickened above to form the lateral arcuate ligament and below to form the iliolumbar ligament.

  • Nerve supply: This muscle is supplied by the lumbar plexus.
  • P.176

  • Action: It fixes or depresses the 12th rib during respiration (see page 102) and laterally flexes the vertebral column to the same side.
Figure 4-33 Muscles and bones forming the posterior abdominal wall.

Transversus Abdominis The transversus abdominis muscle is fully described on page 152. Iliacus The iliacus muscle is fan shaped and arises from the upper part of the iliac fossa (Figs. 4-32 and 4-33). Its fibers join the lateral side of the psoas tendon to be inserted into the lesser trochanter of the femur. The combined muscles are often referred to as the iliopsoas.

Figure 4-34 Case of advanced tuberculous disease of the thoracolumbar region of the vertebral column. A psoas abscess is present, and swellings occur in the right groin above and below the right inguinal ligament.
  • Nerve supply: This muscle is supplied by the femoral nerve, a branch of the lumbar plexus.
  • Action: The iliopsoas flexes the thigh on the trunk at the hip joint, or if the thigh is fixed, it flexes the trunk on the thigh.

The posterior part of the diaphragm (Fig. 4-33) also forms part of the posterior abdominal wall. It is described on page 57. A summary of the muscles of the posterior abdominal P.177
wall, their nerve supply, and their action is given in Table 4-2.

Table 4-2 Muscles of the Posterior Abdominal Wall
Name of Muscle Origin Insertion Nerve Supply Action
Psoas Transverse processes, bodies, and intervertebral discs of 12th thoracic and five lumbar vertebrae With iliacus into lesser trochanter of femur Lumbar plexus Flexes thigh on trunk; if thigh is fixed, it flexes trunk on thigh, as in sitting up from lying position
Quadratus lumborum Iliolumbar ligament, iliac crest, tips of transverse processes of lower lumbar vertebrae 12th rib Lumbar plexus Fixes 12th rib during inspiration; depresses 12th rib during forced expiration; laterally flexes vertebral column same side
Iliacus Iliac fossa With psoas into lesser trochanter of femur Femoral nerve Flexes thigh on trunk; if thigh is fixed, it flexes the trunk on the thigh, as in sitting up from lying position

Fascial Lining of the Abdominal Walls As mentioned previously, the abdominal walls are lined by one continuous layer of connective tissue that lies between the parietal peritoneum and the muscles (Fig. 4-35). It is continuous below with a similar fascial layer lining the pelvic walls. It is customary to name the fascia according to the structure it overlies. For example, the diaphragmatic fascia covers the undersurface of the diaphragm, the transversalis fascia lines the transversus abdominis, the psoas fascia covers the psoas muscle, the quadratus lumborum fascia covers the quadratus lumborum, and the iliaca fascia covers the iliacus muscle. The abdominal blood and lymph vessels lie within this fascial lining, whereas the principal nerves lie outside the fascia. This fact is important in the understanding of the femoral sheath (Fig. 4-35). This is simply a downward prolongation of the fascial lining around the femoral vessels and lymphatics, for about 1.5 in. (4 cm) into the thigh, behind the inguinal ligament. Because the femoral nerve lies outside the fascial envelope, it has no sheath (see page 582). In certain areas of the abdominal wall, the fascial lining performs particularly important functions. Inferior to the level of the anterior superior iliac spines, the posterior wall of the rectus sheath is devoid of muscular aponeuroses (Figs. 4-10 and 4-13) and is formed by the fascia transversalis and peritoneum only (see page 154). Embryologic Notes Development of the Abdominal Wall Following segmentation of the mesoderm, the lateral mesoderm (see page 37) splits into a somatic and a splanchnic layer associated with ectoderm and entoderm, respectively (Fig. 4-36). The muscles of the anterior abdominal wall are derived from the somatopleuric mesoderm and retain their segmental innervation from the anterior rami of the spinal nerves. Unlike the thorax, the segmental arrangement becomes lost due to the absence of ribs, and the mesenchyme fuses to form large sheets of muscle. The rectus abdominis retains indications of its segmental origin, as seen by the presence of the tendinous intersections. The somatopleuric mesoderm becomes split tangentially into three layers, which form the external oblique, internal oblique, and transversus abdominis muscles. The anterior body wall finally closes in the midline at 3 months, when the right and left sides meet in the midline and fuse. The line of fusion of the mesenchyme forms the linea alba, and on either side of this, the rectus muscles come to lie within their rectus sheaths. Development of the Umbilical Cord and the Umbilicus As the tail fold of the embryo develops, the embryonic attachment of the body stalk to the caudal end of the embryonic disc comes to lie on the anterior surface of the embryo, close to the remains of the yolk sac (Fig. 4-37). The amnion and chorion now fuse, so that the amnion encloses the body stalk and the yolk sac with their blood vessels to form the tubular umbilical cord. The mesenchymal core of the cord forms the loose connective tissue called Wharton’s jelly. Embedded in this are the remains of the yolk sac, the vitelline duct, the remains of the allantois, and the umbilical blood vessels. The umbilical vessels consist of two arteries that carry deoxygenated blood from the fetus to the chorion (later the placenta). The two umbilical veins convey oxygenated blood from the placenta to the fetus. The right vein soon disappears (Fig. 4-37). The umbilical cord is a twisted tortuous structure that measures about 0.75 in. (2 cm) in diameter. It increases in length until, at the end of pregnancy, it is about 20 in. (50 cm) long—that is, about the same length as the child. At the midpoint between the anterior superior iliac spine and the symphysis pubis, the spermatic cord pierces the fascia transversalis to form the deep inguinal ring (Fig. 4-8). From the margins of the ring, the fascia is continued over the cord as a tubular sheath, the internal spermatic fascia (Fig. 4-4). Peritoneal Lining of the Abdominal Walls The walls of the abdomen are lined with parietal peritoneum. This is a thin serous membrane consisting of a layer of mesothelium resting on connective tissue. It is continuous below with the parietal peritoneum lining the pelvis (Fig. 4-35). For further details, see pages 352 and 373. Nerve Supply The central part of the diaphragmatic peritoneum is supplied by the phrenic nerves, and the peripheral part is supplied by the lower intercostal nerves. The peritoneum lining the anterior and posterior abdominal walls is supplied segmentally by intercostal and lumbar nerves, which also supply the overlying muscles and skin. P.178

Figure 4-35 Sagittal section of the abdomen showing arrangement of the fascial and peritoneal linings of walls. The femoral sheath with its contained vessels is also shown. Note that the femoral nerve is devoid of a fascial sheath.

P.179

Figure 4-36 Transverse sections through the embryo at different stages of development showing the formation of the abdominal wall and peritoneal cavity. A. The intraembryonic coelom in free communication with the extraembryonic coelom (double-headed arrows). B. The development of the lateral folds of the embryo and the beginning of the closing off of the intraembryonic coelom. C. The lateral folds of the embryo finally fused in the midline and closing off the intraembryonic coelom or future peritoneal cavity. Most of the ventral mesentery will break down and disappear.

P.180

Figure 4-37 The formation of the umbilical cord. Note the expansion of the amniotic cavity (arrows) so that the cord becomes covered with amnion. Note also that the umbilical vessels have been reduced to one vein and two arteries.

Clinical Notes Tying the Cord At birth, the cord is tied off close to the umbilicus. About 2 in. (5 cm) of cord is left between the umbilicus and the ligature, since a piece of intestine may be present as an umbilical hernia in the remains of the extraembryonic coelom. After application of the ligature, the umbilical vessels constrict and thrombose. Later, the stump of the cord is shed and the umbilical scar tissue becomes retracted and assumes the shape of the umbilicus, or navel. Patent Urachus The urachus is the remains of the allantois of the fetus and normally persists as a fibrous cord that runs from the apex of the bladder to the umbilicus. Occasionally, the cavity of the allantois persists, and urine passes from the bladder through the umbilicus. In newborns, it usually reveals itself when a congenital urethral obstruction is present. More often, it remains undiscovered until old age, when enlargement of the prostate may obstruct the urethra (Fig. 4-38). Vitellointestinal Duct The vitelline duct in the early embryo connects the developing gut to the yolk sac. Normally, as development proceeds, the duct is obliterated, severs its connection with the small intestine, and disappears. Persistence of the vitellointestinal duct can result in an umbilical fecal fistula (Fig. 4-38). If the duct remains as a fibrous band, a loop of bowel can become wrapped around it, causing intestinal obstruction (Fig. 4-38).

Figure 4-38 Umbilicus and some common congenital defects.

Meckel’s diverticulum is a congenital anomaly representing a persistent portion of the vitellointestinal duct. It occurs in 2% of patients (Fig. 4-38), is located about 2 ft (61 cm) from the ileocolic junction, and is about 2 in. (5 cm) long. It can become ulcerated or cause intestinal obstruction. Umbilical Vessel Catheterization The umbilical cord is surrounded by the fetal membrane, amnion, and contains Wharton’s jelly. Embedded in this jelly are the remains of the vitellointestinal duct and the allantois, and the single umbilical vein and the two umbilical arteries (Fig. 4-39). The vein is a larger thin-walled vessel and is located at the 12 o’clock position when facing the umbilicus; the two arteries, which lie adjacent to one another and are located at the 4 and 8 o’clock positions when facing the umbilicus, are smaller and thick walled.

Figure 4-39 Catheterization of the umbilical blood vessels. Arrangement of the single umbilical vein and the two umbilical arteries in the umbilical cord and the paths taken by the catheter in the umbilical vein and the umbilical artery.

Indications for Umbilical Artery Catheterization

  • Administration of fluids or blood for resuscitation purposes
  • Arterial blood gas and blood pressure monitoring. The umbilical arteries may be cannulated most easily during the first few hours after birth, but they may be cannulated up to 6 days after delivery.

Anatomy of Procedure One of the small, thick-walled arteries is identified in the Wharton’s jelly in the umbilical stump. Because the umbilical arteries are branches of the internal iliac arteries in the pelvis, the catheter is introduced and advanced slowly in the direction of the feet. The catheter can be inserted for about 2.75 in. (7 cm) in a premature infant and 4.75 in. (12 cm) in a full-term infant. The course of the catheter can be confirmed on a radiograph and is as follows: (a) umbilical artery (directed downward into the pelvis), (b) internal iliac artery (acute turn into this artery), and (c) common iliac artery and the aorta. Anatomy of Complications

  • Catheter perforates arterial wall at a point where the artery turns downward toward the pelvis at the anterior abdominal wall.
  • Catheter enters the thin-walled wider umbilical vein instead of the thick-walled smaller artery.
  • Catheter enters the thin-walled persistent urachus (urine is returned into catheter).
  • Vasospasm of the umbilical and the iliac arteries occurs, causing blanching of the leg.
  • Perforation of arteries distal to the umbilical artery occurs, for example, the iliac arteries or even the aorta.
  • Other complications include thrombosis, emboli, and infection of the umbilical stump.

Indications for Umbilical Vein Catheterization

  • Administration of fluids or blood for resuscitation purposes
  • Exchange transfusions. The umbilical vein may be cannulated up to 7 days after birth.

Anatomy of Procedure The umbilical vein is located in the cord stump at the 12 o’clock position (Fig. 4-39), as described previously, and is easily recognized because of its thin wall and large lumen. The catheter is advanced gently and is directed toward the head, because the vein runs in the free margin of the falciform ligament to join the ductus venosus at the porta hepatis. The catheter may be advanced about 2 in. (5 cm) in a full-term infant. The course of the catheter may be confirmed by radiography and is as follows: (a) the umbilical vein, (b) the ductus venosus, and (c) the inferior vena cava (4 to 4.75 in. [10 to 12 cm]). Anatomy of the Complications of Umbilical Vein Catheterization

  • Catheter may perforate the venous wall. This is most likely to occur where the vein turns cranially at the abdominal wall.
  • Other complications include liver necrosis, hemorrhage, and infection.

Abdominal Herniae A hernia is the protrusion of part of the abdominal contents beyond the normal confines of the abdominal wall (Fig. 4-40). It consists of three parts: the sac, the contents of the sac, and the coverings of the sac. The hernial sac is a pouch (diverticulum) of peritoneum and has a neck and a body. The hernial contents may consist of any structure found within the abdominal cavity and may vary from a small piece of omentum to a large viscus such as the kidney. The hernial coverings are formed from the layers of the abdominal wall through which the hernial sac passes. Abdominal herniae are of the following common types:

  • Inguinal (indirect or direct)
  • Femoral
  • Umbilical (congenital or acquired)
  • Epigastric
    Figure 4-40 Different parts of a hernia.
  • Separation of the recti abdominis
  • Incisional
  • Hernia of the linea semilunaris (Spigelian hernia)
  • Lumbar (Petit’s triangle hernia)
  • Internal

Indirect Inguinal Hernia The indirect inguinal hernia is the most common form of hernia and is believed to be congenital in origin (Fig. 4-41A). The hernial sac is the remains of the processus vaginalis (an outpouching of peritoneum that in the fetus is responsible for the formation of the inguinal canal [see page 165]). It follows that the sac enters the inguinal canal through the deep inguinal ring lateral to the inferior epigastric vessels (Fig. 4-41). It may extend part of the way along the canal or the full length, as far as the superficial inguinal ring. If the processus vaginalis has undergone no obliteration, then the hernia is complete and extends through the superficial inguinal ring down into the scrotum or labium majus. Under these circumstances the neck of the hernial sac lies at the deep inguinal ring lateral to the inferior epigastric vessels, and the body of the sac resides in the inguinal canal and scrotum (or base of labium majus). An indirect inguinal hernia is about 20 times more common in males than in females, and nearly one third are bilateral. It is more common on the right (normally, the right processus vaginalis becomes obliterated after the left; the right testis descends later than the left). It is most common in children and young adults. The indirect inguinal hernia can be summarized as follows:

  • It is the remains of the processus vaginalis and therefore is congenital in origin.
  • It is more common than a direct inguinal hernia.
  • It is much more common in males than females.
  • It is more common on the right side.
  • It is most common in children and young adults.
    Figure 4-41 A. Indirect inguinal hernia. B. Direct inguinal hernia. Note that the neck of the indirect inguinal hernia lies lateral to the inferior epigastric artery, and the neck of the direct inguinal hernia lies medial to the inferior epigastric artery.
  • The hernial sac enters the inguinal canal through the deep inguinal ring and lateral to the inferior epigastric vessels. The neck of the sac is narrow.
  • The hernial sac may extend through the superficial inguinal ring above and medial to the pubic tubercle. (Femoral hernia is located below and lateral to the pubic tubercle.)
  • The hernial sac may extend down into the scrotum or labium majus.

Direct Inguinal Hernia The direct inguinal hernia makes up about 15% of all inguinal hernias. The sac of a direct hernia bulges directly anteriorly through the posterior wall of the inguinal canal medial to the inferior epigastric vessels (Fig. 4-41B). Because of the presence of the strong conjoint tendon (combined tendons of insertion of the internal oblique and transversus muscles), this hernia is usually nothing more than a generalized bulge; therefore, the neck of the hernial sac is wide. Direct inguinal hernias are rare in women and most are bilateral. It is a disease of old men with weak abdominal muscles. A direct inguinal hernia can be summarized as follows:

  • It is common in old men with weak abdominal muscles and is rare in women.
  • The hernial sac bulges forward through the posterior wall of the inguinal canal medial to the inferior epigastric vessels.
  • The neck of the hernial sac is wide.

An inguinal hernia can be distinguished from a femoral hernia by the fact that the sac, as it emerges through the superficial inguinal ring, lies above and medial to the pubic tubercle, whereas that of a femoral hernia lies below and lateral to the tubercle (Fig. 4-42). Femoral Hernia The hernial sac descends through the femoral canal within the femoral sheath, creating a femoral hernia. The femoral sheath, which is fully described on page 579, is a protrusion of the fascial envelope lining the abdominal walls and surrounds the femoral vessels and lymphatics for about 1 in. (2.5 cm) below the inguinal ligament (Fig. 4-43). The femoral artery, as it enters the thigh below the inguinal ligament, occupies the lateral compartment of the sheath. The femoral vein, which lies on its medial side and is separated from it by a fibrous septum, occupies the intermediate compartment. The lymph vessels, which are separated from the vein by a fibrous septum, occupy the most medial compartment. The femoral canal, the compartment for the lymphatics, occupies the medial part of the sheath. It is about 0.5 in. (1.3 cm) long, and its upper opening is referred to as the femoral ring. The femoral septum, which is a condensation of extraperitoneal tissue, plugs the opening of the femoral ring.

Figure 4-42 Relation of inguinal and femoral hernial sacs to the pubic tubercle.

A femoral hernia is more common in women than in men (possibly because of a wider pelvis and femoral canal). The hernial sac passes down the femoral canal, pushing the femoral septum before it. On escaping through the lower end, it expands to form a swelling in the upper part of the thigh deep to the deep fascia (Fig. 4-43). With further expansion, the hernial sac may turn upward to cross the anterior surface of the inguinal ligament. The neck of the sac always lies below and lateral to the pubic tubercle (Fig. 4-42), which serves to distinguish it from an inguinal hernia. The neck of the sac is narrow and lies at the femoral ring. The ring is related anteriorly to the inguinal ligament, posteriorly to the pectineal ligament and the pubis, medially to the sharp free edge of the lacunar ligament, and laterally to the femoral vein. Because of the presence of these anatomic structures, the neck of the sac is unable to expand. Once an abdominal viscus has passed through the neck into the body of the sac, it may be difficult to push it up and return it to the abdominal cavity (irreducible hernia). Furthermore, after straining or coughing, a piece of bowel may be forced through the neck and its blood vessels may be compressed by the femoral ring, seriously impairing its blood supply (strangulated hernia). A femoral hernia is a dangerous disease and should always be treated surgically. A femoral hernia can be summarized as follows:

  • It is a protrusion of abdominal parietal peritoneum down through the femoral canal to form the hernial sac.
  • It is more common in women than in men.
  • The neck of the hernial sac lies below and lateral to the pubic tubercle.
  • The neck of the hernial sac lies at the femoral ring and at that point is related anteriorly to the inguinal ligament, posteriorly to the pectineal ligament and the pubis, laterally to the femoral vein, and medially to the sharp free edge of the lacunar ligament.

Umbilical Herniae Congenital umbilical hernia, or exomphalos (omphalocele), is caused by a failure of part of the midgut to return to the abdominal cavity from the extraembryonic coelom during fetal life. The hernial sac and its relationship to the umbilical cord are shown in Figure 4-44. Acquired infantile umbilical hernia is a small hernia that sometimes occurs in children and is caused by a weakness in the scar of the umbilicus in the linea alba (Fig. 4-44). Most become smaller and disappear without treatment as the abdominal cavity enlarges. Acquired umbilical hernia of adults is more correctly referred to as a paraumbilical hernia. The hernial sac does not protrude through the umbilical scar, but through the linea alba in the region of the umbilicus (Fig. 4-44). Paraumbilical herniae gradually increase in size and hang downward. The neck of the sac may be narrow, but the body of the sac often contains coils of small and large intestine and omentum. Paraumbilical herniae are much more common in women than in men. Epigastric Hernia Epigastric hernia occurs through the widest part of the linea alba, anywhere between the xiphoid process and the umbilicus. The hernia is usually small and starts off as a small protrusion of extraperitoneal fat between the fibers of the linea alba. During the following months or years the fat is forced farther through the linea alba and eventually drags behind it a small peritoneal sac. The body of the sac often contains a small piece of greater omentum. It is common in middle-aged manual workers.

Figure 4-43 The femoral sheath as seen from below. Arrow emerging from the femoral canal indicates the path taken by the femoral hernial sac. Note relations of the femoral ring.

Separation of the Recti Abdominis Separation of the recti abdominis occurs in elderly multiparous women with weak abdominal muscles (Fig. 4-44). In this condition, the aponeuroses forming the rectus sheath become excessively stretched. When the patient coughs or strains, the recti separate widely, and a large hernial sac, containing abdominal viscera, bulges forward between the medial margins of the recti. This can be corrected by wearing a suitable abdominal belt. Incisional Hernia A postoperative incisional hernia is most likely to occur in patients in whom it was necessary to cut one of the segmental nerves supplying the muscles of the anterior abdominal wall; postoperative wound infection with death (necrosis) of the abdominal musculature is also a common cause. The neck of the sac is usually large, and adhesion and strangulation of its contents are rare complications. In very obese individuals the extent of the abdominal wall weakness is often difficult to assess. Hernia of the Linea Semilunaris (Spigelian Hernia) The uncommon hernia of the linea semilunaris occurs through the aponeurosis of the transversus abdominis just lateral to the lateral edge of the rectus sheath. It usually occurs just below the level of the umbilicus. The neck of the sac is narrow, so that adhesion and strangulation of its contents are common complications. Lumbar Hernia The lumbar hernia occurs through the lumbar triangle and is rare. The lumbar triangle (Petit’s triangle) is a weak area in the posterior part of the abdominal wall. It is bounded anteriorly by the posterior margin of the external oblique muscle, posteriorly by the anterior border of the latissimus dorsi muscle, and inferiorly by the iliac crest. The floor of the triangle is formed by the internal oblique and the transversus abdominis muscles. The neck of the hernia is usually large, and the incidence of strangulation low. Internal Hernia Occasionally, a loop of intestine enters a peritoneal recess (e.g., the lesser sac or the duodenal recesses) and becomes strangulated at the edges of the recess (see page 214). Abdominal Stab Wounds Abdominal stab wounds may or may not penetrate the parietal peritoneum and violate the peritoneal cavity and consequently may or may not significantly damage the abdominal viscera. The structures in the various layers through which an abdominal stab wound penetrates depend on the anatomic location.

Figure 4-44 A. Congenital umbilical hernia. B. Infantile umbilical hernia. C. Paraumbilical hernia. D. Epigastric hernia. E. Separation of recti abdominis.

Lateral to the rectus sheath are the following: skin, fatty layer of superficial fascia, membranous layer of superficial fascia, thin layer of deep fascia, external oblique muscle or aponeurosis, internal oblique muscle or aponeurosis, transversus abdominis muscle or aponeurosis, fascia transversalis, extraperitoneal connective tissue (often fatty), and parietal peritoneum. Anterior to the rectus sheath are the following: skin, fatty layer of superficial fascia, membranous layer of superficial fascia, thin layer of deep fascia, anterior wall of rectus sheath, rectus abdominis muscle with segmental nerves and epigastric vessels lying behind the muscle, posterior wall of rectus sheath, fascia transversalis, extraperitoneal connective tissue (often fatty), and parietal peritoneum. In the midline are the following: skin, fatty layer of superficial fascia, membranous layer of superficial fascia, thin layer of deep fascia, fibrous linea alba, fascia transversalis, extraperitoneal connective tissue (often fatty), and parietal peritoneum. In an abdominal stab wound, washing out the peritoneal cavity with saline solution (peritoneal lavage) can be used to determine whether any damage to viscera or blood vessels has occurred. Abdominal Gunshot Wounds Gunshot wounds are much more serious than stab wounds; in most patients, the peritoneal cavity has been entered, and significant visceral damage has ensued. Surgical Incisions The length and direction of surgical incisions through the anterior abdominal wall to expose the underlying viscera are largely governed by the position and direction of the nerves of the abdominal wall, the direction of the muscle fibers, and the arrangement of the aponeuroses forming the rectus sheath. Ideally, the incision should be made in the direction of the lines of cleavage in the skin so that a hairline scar is produced. The surgeon usually has to compromise, placing the safety of the patient first and the cosmetic result second. Incisions that necessitate the division of one of the main segmental nerves lying within the abdominal wall result in paralysis of part of the anterior abdominal musculature and a segment of the rectus abdominis. The consequent weakness of the abdominal musculature causes an unsightly bulging forward of the abdominal wall and visceroptosis; extreme cases may require a surgical belt for support. If the incision can be made in the line of the muscle fibers or aponeurotic fibers as each layer is traversed, on closing the incision the fibers fall back into position and function normally. Incisions through the rectus sheath are widely used, provided that the rectus abdominis muscle and its nerve supply are kept intact. On closure of the incisions, the anterior and posterior walls of the sheath are sutured separately, and the rectus muscle springs back into position between the suture lines. The result is a very strong repair, with minimum interference with function. The following incisions are commonly used.

  • Paramedian incision: This may be supraumbilical, for exposure of the upper part of the abdominal cavity, or infraumbilical, for the lower abdomen and pelvis. In extensive operations in which a large exposure is required, the incision can run the full length of the rectus sheath. The anterior wall of the rectus sheath is exposed and incised about 1 in. (2.5 cm) from the midline. The medial edge of the incision is dissected medially, freeing the anterior wall of the sheath from the tendinous intersections of the rectus muscle. The rectus abdominis muscle is retracted laterally with its nerve supply intact, and the posterior wall of the sheath is exposed. The posterior wall is then incised, together with the fascia transversalis and the peritoneum. The wound is closed in layers.
  • Pararectus incision: The anterior wall of the rectus sheath is incised medially and parallel to the lateral margin of the rectus muscle. The rectus is freed and retracted medially, exposing the segmental nerves entering its posterior surface. If the opening into the abdominal cavity is to be small, these nerves may be retracted upward and downward. The posterior wall of the sheath is then incised, as in the paramedian incision. The great disadvantage of this incision is that the opening is small, and any longitudinal extension requires that one or more segmental nerves to the rectus abdominis be divided, with resultant postoperative rectus muscle weakness.
  • Midline incision: This incision is made through the linea alba. The fascia transversalis, the extraperitoneal connective tissue, and the peritoneum are then incised. It is easier to perform above the umbilicus because the linea alba is wider in that region. It is a rapid method of gaining entrance to the abdomen and has the obvious advantage that it does not damage muscles or their nerve and blood supplies. Midline incision has the additional advantage that it may be converted into a T-shaped incision for greater exposure. The anterior and posterior walls of the rectus sheath are then cut across transversely, and the rectus muscle is retracted laterally.
  • Transrectus incision: The technique of making and closing of this incision is the same as that used in the paramedian incision, except that the rectus abdominis muscle is incised longitudinally and not retracted laterally from the midline. This incision has the great disadvantage of sectioning the nerve supply to that part of the muscle that lies medial to the muscle incision.
  • Transverse incision: This can be made above or below the umbilicus and can be small or so large that it extends from flank to flank. It can be made through the rectus sheath and the rectus abdominis muscles and through the oblique and transversus abdominis muscles laterally. It is rare to damage more than one segmental nerve so that postoperative abdominal weakness is minimal. The incision gives good exposure and is well tolerated by the patient. Closure of the wound is made in layers. It is unnecessary to suture the cut ends of the rectus muscles, provided that the sheaths are carefully repaired.
  • Muscle splitting, or McBurney’s incision: This is chiefly used for cecostomy and appendectomy. It gives a limited exposure only, and should any doubt arise about the diagnosis, an infraumbilical right paramedian incision should be used instead.

An oblique skin incision is made in the right iliac region about 2 in. (5 cm) above and medial to the anterior superior iliac spine. The external and internal oblique and transversus muscles are incised or split in the line of their fibers and retracted to expose the fascia transversalis and the peritoneum. The latter are now incised and the abdominal cavity is opened. The incision is closed in layers, with no postoperative weakness.

  • Abdominothoracic incision: This is used to expose the lower end of the esophagus, as, for example, in esophagogastric resection for carcinoma of this region. An upper oblique or paramedian abdominal incision is extended upward and laterally into the seventh, eighth, or ninth intercostal space, the costal arch is transected, and the diaphragm is incised. Wide exposure of the upper abdomen and thorax is then obtained by the use of a rib-spreading retractor.

On completion of the operation, the diaphragm is repaired with nonabsorbable sutures, the costal margin is reconstructed, and the abdominal and thoracic wounds are closed. Paracentesis of the Abdomen Paracentesis of the abdomen may be necessary to withdraw excessive collections of peritoneal fluid, as in ascites secondary to cirrhosis of the liver or malignant ascites secondary to advanced ovarian cancer. Under a local anesthetic, a needle or catheter is inserted through the anterior abdominal wall. The underlying coils of intestine are not damaged because they are mobile and are pushed away by the cannula.

Figure 4-45 Paracentesis of the abdominal cavity in midline (1) and laterally (2).
Figure 4-46 Peritoneal lavage. A. The two common sites used in this procedure. Note the positions of the superior and inferior epigastric arteries in the rectus sheath. B. Cross section of the anterior abdominal wall in the midline. Note the structures pierced by the catheter. C. Cross section of the anterior abdominal wall just lateral to the umbilicus. Note the structures pierced by the catheter. The rectus muscle has been retracted laterally.

If the cannula is inserted in the flank (Fig. 4-45) lateral to the inferior epigastric artery and above the deep circumflex artery, it will pass through the following: skin, superficial fascia, deep fascia (very thin), aponeurosis or muscle of external oblique, internal oblique muscle, transversus abdominis muscle, fascia transversalis, extraperitoneal connective tissue (fatty), and parietal peritoneum. Anatomy of Peritoneal Lavage Peritoneal lavage is used to sample the intraperitoneal space for evidence of damage to viscera and blood vessels. It is generally employed as a diagnostic technique in certain cases of blunt abdominal trauma. In nontrauma situations, peritoneal lavage has been used to confirm the diagnosis of acute pancreatitis and primary peritonitis, to correct hypothermia, and to conduct dialysis. The patient is placed in the supine position and the urinary bladder is emptied by catheterization. In small children the bladder is an abdominal organ (see page 348); in adults, the full bladder may rise out of the pelvis and reach as high as the umbilicus (see page 330). The stomach is emptied by a nasogastric tube because a distended stomach may extend to the anterior abdominal wall. The skin is anesthetized and a 2.25-in. (3-cm) vertical incision is made. Midline Incision Technique The following anatomic structures are penetrated, in order, to reach the parietal peritoneum (Fig. 4-46): skin, fatty layer of superficial fascia, membranous layer of superficial fascia, thin layer of deep fascia, linea alba, fascia transversalis, extraperitoneal fat, and parietal peritoneum. Paraumbilical Incision Technique The following anatomic structures are penetrated, in order, to reach the parietal peritoneum (Fig. 4-46): skin, fatty layer of superficial fascia, membranous layer of superficial fascia, thin layer of deep fascia, anterior wall of rectus sheath, the rectus abdominis muscle is retracted, posterior wall of the rectus sheath, fascia transversalis, extraperitoneal fat, and parietal peritoneum. It is important that all the small blood vessels in the superficial fascia be secured, because bleeding into the peritoneal cavity might produce a false-positive result. These vessels are the terminal branches of the superficial and deep epigastric arteries and veins. Anatomy of the Complications of Peritoneal Lavage

  • In the midline technique, the incision or trocar may miss the linea alba, enter the rectus sheath, traverse the vascular rectus abdominis muscle and encounter branches of the epigastric vessels. Bleeding from this source could produce a false-positive result.
  • Perforation of the gut by the scalpel or trocar
  • Perforation of the mesenteric blood vessels or vessels on the posterior abdominal wall or pelvic walls
  • Perforation of a full bladder
  • Wound infection

Endoscopic Surgery Endoscopic surgery on the gallbladder, bile ducts, and the appendix has become a common procedure. It involves the passage of the endoscope into the peritoneal cavity through small incisions in the anterior abdominal wall. The anatomic structures traversed by the instruments are similar to those enumerated for peritoneal lavage. Great care must be taken to preserve the integrity of the segmental nerves as they course down from the costal margin to supply the abdominal musculature. The advantages of this surgical technique are that the anatomic and physiologic features of the anterior abdominal wall are disrupted only minimally and, consequently, convalescence is brief. The great disadvantages are that the surgical field is small and the surgeon is limited in the extent of the operation (Fig. 4-47).

Figure 4-47 Inguinal canal anatomy as viewed during laparoscopic exploration of the peritoneal cavity. A. The normal anatomy of the inguinal region from within the peritoneal cavity. Black arrow indicates the closed deep inguinal ring; white arrow, the inferior epigastric vessels. B. An indirect inguinal hernia. Curved black arrow indicates the mouth of the hernial sac; white arrow, the inferior epigastric vessels. (Courtesy of N.S. Adzick.)

P.181
P.182
P.183
P.184
P.185
P.186
P.187
P.188
P.189
P.190
P.191
Radiographic Anatomy For a detailed discussion, see page 282. Surface Anatomy Surface Landmarks of the Abdominal Wall Xiphoid Process The xiphoid process is the thin cartilaginous lower part of the sternum. It is easily palpated in the depression where the costal margins meet in the upper part of the anterior abdominal wall (Figs. 4-11 and 4-12). The xiphisternal junction is identified by feeling the lower edge of the body of the sternum, and it lies opposite the body of the ninth thoracic vertebra. Costal Margin The costal margin is the curved lower margin of the thoracic wall and is formed in front by the cartilages of the 7th, 8th, 9th, and 10th ribs (Figs. 4-11 and 4-12) and behind by the cartilages of the 11th and 12th ribs. The costal margin reaches its lowest level at the 10th costal cartilage, which lies opposite the body of the third lumbar vertebra. The 12th rib may be short and difficult to palpate. Iliac Crest The iliac crest can be felt along its entire length and ends in front at the anterior superior iliac spine (Figs. 4-11 and 4-12) and behind at the posterior superior iliac spine (Fig. 4-49). Its highest point lies opposite the body of the fourth lumbar vertebra. About 2 in. (5 cm) posterior to the anterior superior iliac spine, the outer margin projects to form the tubercle of the crest (Fig. 4-12). The tubercle lies at the level of the body of the fifth lumbar vertebra. Pubic Tubercle The pubic tubercle is an important surface landmark. It may be identified as a small protuberance along the superior surface of the pubis (Figs. 4-3, 4-12, and 4-32). Symphysis Pubis The symphysis pubis is the cartilaginous joint that lies in the midline between the bodies of the pubic bones (Fig. 4-11). It is felt as a solid structure beneath the skin in the midline at the lower extremity of the anterior abdominal wall. The pubic crest is the name given to the ridge on the superior surface of the pubic bones medial to the pubic tubercle (Fig. 4-32). Inguinal Ligament The inguinal ligament lies beneath a skin crease in the groin. It is the rolled-under inferior margin of the aponeurosis of the external oblique muscle (Figs. 4-2, 4-6, and 4-11). It is attached laterally to the anterior superior iliac spine and curves downward and medially, to be attached to the pubic tubercle. Superficial Inguinal Ring The superficial inguinal ring is a triangular aperture in the aponeurosis of the external oblique muscle and is situated above and medial to the pubic tubercle (Figs. 4-2, 4-3, 4-8, and 4-12). In the adult male, the margins of the ring can be felt by invaginating the skin of the upper part of the scrotum with the tip of the little finger. The soft tubular spermatic cord can be felt emerging from the ring and descending over or medial to the pubic tubercle into the scrotum (Fig. 4-8). Palpate the spermatic cord in the upper part of the scrotum between the finger and thumb and note the presence of a firm cordlike structure in its posterior part called the vas deferens (Figs. 4-5 and 4-21). In the female, the superficial inguinal ring is smaller and difficult to palpate; it transmits the round ligament of the uterus. Scrotum The scrotum is a pouch of skin and fascia containing the testes, the epididymides, and the lower ends of the spermatic cords. The skin of the scrotum is wrinkled and is covered with sparse hairs. The bilateral origin of the scrotum is indicated by the presence of a dark line in the midline, called the scrotal raphe, along the line of fusion. The testis on each side is a firm ovoid body surrounded on its lateral, anterior, and medial surfaces by the two layers of the tunica vaginalis (Fig. 4-21). The testis should therefore lie free and not tethered to the skin or subcutaneous tissue. Posterior to the testis is an elongated structure, the epididymis (Fig. 4-21). It has an enlarged upper end called the head, a body, and a narrow lower end, the tail. The vas deferens emerges from the tail and ascends medial to the epididymis to enter the spermatic cord at the upper end of the scrotum. Linea Alba The linea alba is a vertically running fibrous band that extends from the symphysis pubis to the xiphoid process and lies in the midline (Fig. 4-3). It is formed by the fusion of the aponeuroses of the muscles of the anterior abdominal wall and is represented on the surface by a slight median groove (Figs. 4-11 and 4-12). Umbilicus The umbilicus lies in the linea alba and is inconstant in position. It is a puckered scar and is the site of attachment of the umbilical cord in the fetus. Rectus Abdominis The rectus abdominis muscles lie on either side of the linea alba (Fig. 4-11) and run vertically in the abdominal wall; they can be made prominent by asking the patient to raise the shoulders while in the supine position without using the arms. Tendinous Intersections of the Rectus Abdominis The tendinous intersections are three in number and run across the rectus abdominis muscle. In muscular individuals P.192
they can be palpated as transverse depressions at the level of the tip of the xiphoid process, at the umbilicus, and halfway between the two (Fig. 4-11). Linea Semilunaris The linea semilunaris is the lateral edge of the rectus abdominis muscle and crosses the costal margin at the tip of the ninth costal cartilage (Figs. 4-11 and 4-12). To accentuate the semilunar lines, the patient is asked to lie on the back and raise the shoulders off the couch without using the arms. To accomplish this, the patient contracts the rectus abdominis muscles so that their lateral edges stand out. Abdominal Lines and Planes Vertical lines and horizontal planes (Fig. 4-12) are commonly used to facilitate the description of the location of diseased structures or the performing of abdominal procedures. Vertical Lines Each vertical line (right and left) passes through the midpoint between the anterior superior iliac spine and the symphysis pubis. Transpyloric Plane The horizontal transpyloric plane passes through the tips of the ninth costal cartilages on the two sides—that is, the point where the lateral margin of the rectus abdominis (linea semilunaris) crosses the costal margin (Fig. 4-12). It lies at the level of the body of the first lumbar vertebra. This plane passes through the pylorus of the stomach, the duodenojejunal junction, the neck of the pancreas, and the hila of the kidneys. Subcostal Plane The horizontal subcostal plane joins the lowest point of the costal margin on each side—that is, the 10th costal cartilage (Fig. 4-12). This plane lies at the level of the third lumbar vertebra. Intercristal Plane The intercristal plane passes across the highest points on the iliac crests and lies on the level of the body of the fourth lumbar vertebra. This is commonly used as a surface landmark when performing a lumbar spinal tap (see page 871). Intertubercular Plane The horizontal intertubercular plane joins the tubercles on the iliac crests (Fig. 4-12) and lies at the level of the fifth lumbar vertebra. Abdominal Quadrants It is common practice to divide the abdomen into quadrants by using a vertical and a horizontal line that intersect at the umbilicus (Fig. 4-12). The quadrants are the upper right, upper left, lower right, and lower left. The terms epigastrium and periumbilical are loosely used to indicate the area below the xiphoid process and above the umbilicus and the area around the umbilicus, respectively. Surface Landmarks of the Abdominal Viscera It must be emphasized that the positions of most of the abdominal viscera show individual variations as well as variations in the same person at different times. Posture and respiration have a profound influence on the position of viscera. The following organs are more or less fixed, and their surface markings are of clinical value. Liver The liver lies under cover of the lower ribs, and most of its bulk lies on the right side (Fig. 4-48). In infants, until about the end of the third year, the lower margin of the liver extends one or two fingerbreadths below the costal margin (Fig. 4-48). In the adult who is obese or has a well-developed right rectus abdominis muscle, the liver is not palpable. In a thin adult, the lower edge of the liver may be felt a fingerbreadth below the costal margin. It is most easily felt when the patient inspires deeply and the diaphragm contracts and pushes down the liver. Gallbladder The fundus of the gallbladder lies opposite the tip of the right ninth costal cartilage—that is, where the lateral edge of the right rectus abdominis muscle crosses the costal margin (Fig. 4-48). Spleen The spleen is situated in the left upper quadrant and lies under cover of the 9th, 10th, and 11th ribs (Fig. 4-48). Its long axis corresponds to that of the 10th rib, and in the adult it does not normally project forward in front of the midaxillary line. In infants, the lower pole of the spleen may just be felt (Fig. 4-48). Pancreas The pancreas lies across the transpyloric plane. The head lies below and to the right, the neck lies on the plane, and the body and tail lie above and to the left. Kidneys The right kidney lies at a slightly lower level than the left kidney (because of the bulk of the right lobe of the liver), and the lower pole can be palpated in the right lumbar region at the end of deep inspiration in a person with poorly developed abdominal muscles. Each kidney moves about 1 in. (2.5 cm) in a vertical direction during full respiratory movement of the diaphragm. The normal left kidney, which is higher than the right kidney, is not palpable. On the anterior abdominal wall the hilum of each kidney lies on the transpyloric plane, about three fingerbreadths from the midline (Fig. 4-49). On the back, the kidneys extend from the 12th thoracic spine to the third lumbar spine, and the hili are opposite the first lumbar vertebra (Fig. 4-49). P.193

Figure 4-48 Surface markings of the fundus of the gallbladder, spleen, and liver. In a young child, the lower margin of the normal liver and the lower pole of the normal spleen can be palpated. In a thin adult, the lower margin of the normal liver may just be felt at the end of deep inspiration.

Stomach The cardioesophageal junction lies about three fingerbreadths below and to the left of the xiphisternal junction (the esophagus pierces the diaphragm at the level of the 10th thoracic vertebra). The pylorus lies on the transpyloric plane just to the right of the midline. The lesser curvature lies on a curved line joining the cardioesophageal junction and the pylorus. The greater curvature has an extremely variable position in the umbilical region or below. Duodenum (First Part) The duodenum lies on the transpyloric plane about four fingerbreadths to the right of the midline. Cecum The cecum is situated in the right lower quadrant. It is often distended with gas and gives a resonant sound when percussed. It can be palpated through the anterior abdominal wall. P.194
P.195

Figure 4-49 A. Surface anatomy of the kidneys and ureters on the anterior abdominal wall. Note the relationship of the hilum of each kidney to the transpyloric plane. B. Surface anatomy of the kidneys on the posterior abdominal wall.

Appendix The appendix lies in the right lower quadrant. The base of the appendix is situated one third of the way up the line, joining the anterior superior iliac spine to the umbilicus (McBurney’s point). The position of the free end of the appendix is variable. Ascending Colon The ascending colon extends upward from the cecum on the lateral side of the right vertical line and disappears under the right costal margin. It can be palpated through the anterior abdominal wall. Transverse Colon The transverse colon extends across the abdomen, occupying the umbilical region. It arches downward with its concavity directed upward. Because it has a mesentery, its position is variable. Descending Colon The descending colon extends downward from the left costal margin on the lateral side of the left vertical line. In the left lower quadrant it curves medially and downward to become continuous with the sigmoid colon. The descending colon has a smaller diameter than the ascending colon and can be palpated through the anterior abdominal wall. Urinary Bladder and Pregnant Uterus The full bladder and pregnant uterus can be palpated through the lower part of the anterior abdominal wall above the symphysis pubis (see page 330). Aorta The aorta lies in the midline of the abdomen and bifurcates below into the right and left common iliac arteries opposite the fourth lumbar vertebra—that is, on the intercristal plane. The pulsations of the aorta can be easily palpated through the upper part of the anterior abdominal wall just to the left of the midline. External Iliac Artery The pulsations of this artery can be felt as it passes under the inguinal ligament to become continuous with the femoral artery. It can be located at a point halfway between the anterior superior iliac spine and the symphysis pubis. Clinical Problem Solving Study the following case histories and select the best answer to the questions following them. An obese 40-year-old woman was seen in the emergency department complaining of a severe pain over the right shoulder and in her right side and back below the shoulder blade. She said that she had experienced the pain on several occasions before and that when she ate fatty foods it seemed to make the pain worse. Ultrasound demonstrated the presence of gallstones. Her condition was diagnosed as cholelithiasis, and the pain was attributed to gallstone colic. 1. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The fundus of the gallbladder lies against the anterior abdominal wall next to the tip of the right ninth costal cartilage. (b) The parietal peritoneum in this area is innervated by the 10th and 11th intercostal nerves, which give rise to referred pain in the 10th and 11th dermatomes on the side and back. (c) The parietal peritoneum on the central part of the undersurface of the diaphragm is supplied by the phrenic nerve. (d) The spinal segmental nerves within the phrenic nerve are C3, C4, and C5. (e) The pain was referred to the shoulder along the supraclavicular nerves (C3 and C4). View Answer1. B. The parietal peritoneum in the region of the fundus of the gallbladder is innervated by the eighth and ninth intercostal nerves, which give rise to referred pain in the eighth and ninth thoracic dermatomes on the side and back. An 8-year-old boy was admitted to the hospital with a temperature of 101°F, a furred tongue, and pain in the right lower quadrant. On examination, the skin on the right lower quadrant was tender to the touch, and the abdominal muscles were contracted and rigid. A diagnosis of acute appendicitis was made. 2. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) An acutely inflamed appendix produces an inflammation of the peritoneal coat covering it. (b) Should the inflammatory process spread, for example, if the appendix should rupture, the parietal peritoneum would become involved. (c) The parietal peritoneum, the abdominal muscles, and the overlying skin are supplied by the same segmental spinal nerves. (d) The segmental nerves supplying the right lower quadrant of the abdominal wall are T7, T8, and T9. (e) The pain in the right lower quadrant and the regional contraction of the abdominal muscles are an attempt by the body to keep the inflamed appendix immobile so that the inflammatory process remains localized. View Answer2. D. The segmental nerves supplying the right lower quadrant of the abdominal wall are T11, T12, and L1. A workman engaged in demolishing a building lost his balance and fell astride a girder on the floor below. On examination, he was found to have extensive swelling of his perineum, scrotum, and penis. He was unable to urinate normally, passing only a few drops of blood-stained urine. The lower part of the anterior abdominal wall was also swollen, but his thighs were normal. 3. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The patient’s fall ruptured the urethra in the perineum. (b) When the patient attempted to micturate, the urine extravasated beneath Colles’ fascia. (c) The urine passed over the scrotum and penis under the membranous layer of superficial fascia. (d) The urine passed upward beneath the membranous layer of superficial fascia on the anterior abdominal wall. (e) The urine could not extend posteriorly because of the attachment of Colles’ fascia to the tip of the coccyx. (f) The urine did not extend into the thigh because of the attachment of the membranous layer of superficial fascia to the fascia lata, just below the inguinal ligament. View Answer3. E. The urine could not extend posteriorly because of the attachment of the Colles’ fascia to the posterior edge of the perineal membrane. A 45-year-old woman was shopping in a liquor store when an armed robbery took place. A shoot-out occurred and a bullet ricocheted off the wall and entered her left side. Fortunately, the bullet did not enter the peritoneal cavity. One year later, in addition to diminished skin sensation over the left lumbar region and umbilicus, she noticed a bulging forward of the left side of her anterior abdominal wall. 4. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The bullet cut the 9th and 10th intercostal nerves just below the costal margin on the left side. (b) The diminished skin sensation was caused by the loss of the sensory nerve supply to the 9th and 10th thoracic dermatomes. (c) Portions of the oblique, transversus, and rectus abdominis muscles on the left side were paralyzed. (d) Atrophy of the pyramidalis muscle resulted in loss of support to the abdominal viscera, which then sagged forward. View Answer4. D. The pyramidalis muscle (if present) is innervated by the 12th thoracic nerve. A 9-week-old boy was admitted to the hospital with a swelling in the right groin that extended down into the upper part of the scrotum. When he cried, the swelling enlarged. On careful palpation it was possible to reduce the size of the swelling, and this procedure was accompanied by a gurgling noise. 5. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The swelling was situated above and medial to the pubic tubercle on the right side. (b) The child had a right indirect inguinal hernia. (c) The processus vaginalis in its upper part had failed to become obliterated before birth. (d) The hernial sac in an indirect inguinal hernia emerges from the superficial inguinal ring. (e) The superficial inguinal ring lies above and medial to the pubic tubercle. (f) The contents of the hernial sac consisted only of the greater omentum. View Answer5. F. The contents of this hernial sac included coils of small intestine, which were responsible for the gurgling noises that occurred as the hernia was reduced. A 75-year-old man with chronic bronchitis noticed that a bulge was developing in his left groin. On examination, an elongated swelling was seen above the medial end of the left inguinal ligament. When the patient coughed, the swelling enlarged but did not descend into the scrotum. The patient had weak abdominal muscles. 6. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The inguinal swelling was a direct inguinal hernia. (b) The cause of the hernia was weak abdominal muscles. (c) The hernial sac was wide and in direct communication with the peritoneal cavity. (d) A rise in intra-abdominal pressure on coughing caused the hernial swelling to expand. (e) The swelling occurred lateral to the inferior epigastric artery. View Answer6. E. The swelling occurs medial to the inferior epigastric artery. A 40-year-old woman noticed a painful swelling in her right groin after helping her husband move some heavy furniture. On examination, a small tender swelling was noted in the right groin. 7. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) The excessive exertion caused a rise in intra-abdominal pressure. (b) A hernial sac formed of parietal peritoneum was forced downward. (c) The peritoneum was forced through the right femoral canal. (d) The patient had a right-sided femoral hernia. (e) The neck of a femoral hernial sac is situated below and medial to the pubic tubercle. View Answer7. E. The neck of a femoral hernial sac is situated below and lateral to the pubic tubercle. A 55-year-old man was admitted to the hospital with a large, hard, fixed, intra-abdominal mass. On examination of the abdomen the mass was situated on the transpyloric plane. The inguinal lymph nodes were normal. 8. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) Radiologic examination of the stomach showed nothing abnormal. (b) The right testicle was enlarged and was much harder than normal. (c) A diagnosis of malignant disease of the right testis was made. (d) The malignant tumor had metastasized to the lumbar lymph nodes lying on the transpyloric plane on the posterior abdominal wall, which is the normal lymphatic drainage of the testis. (e) In malignant disease of the testis the superficial inguinal lymph nodes only become involved if the tumor spreads to involve the scrotal skin. (f) The normal testis is tethered to the skin of the scrotum. View Answer8. F. The normal testis is freely mobile within the scrotum and is not tethered to the subcutaneous tissue or skin. A 25-year-old man involved in purchasing drugs was knifed in the abdomen in the left upper quadrant. On examination in the emergency department, it was difficult to determine whether the knife had penetrated into the peritoneal cavity. It was decided to do a midline peritoneal lavage below the umbilicus to see if there was any free blood in the peritoneal cavity. 9. The following layers of tissue were penetrated by the trocar and cannula to enter the peritoneal cavity except which? (a) Skin (b) Fatty and membranous layers of superficial fascia (c) Rectus sheath and rectus abdominis muscle (d) Deep fascia (e) Fascia transversalis (f) Extraperitoneal tissue and parietal peritoneum View Answer9. C. The linea alba lies in the midline; the rectus sheath lies lateral to the linea alba. A 20-year-old soccer player was accidentally kicked on the left side of her chest. On returning to the locker room she said she felt faint and collapsed to the floor. On examination in the emergency department, she was found to be in hypovolemic shock. She had tenderness and muscle rigidity in the left upper quadrant of her abdomen. She also had extreme local tenderness over her left 10th rib in the midaxillary line. 10. The symptoms and signs displayed by this patient can be explained by the following statements except which? (a) Radiology revealed a fractured left 10th rib. (b) The spleen was severely bruised and the bloolass=”A”>(c) Later in the locker room the capsule of the spleen gave way and the blood escaped into the peritoneal cavity. (d) Blood does not irritate the parietal peritoneum. (e) Stimulation of the sensory nerves supplying the parietal peritoneum was responsible for the extreme tenderness of the left upper quadrant of the abdomen. (f) The muscles forming the anterior abdominal wall in that region were reflexly stimulated, producing muscle rigidity. View Answer10. D. Blood is very irritating to the parietal peritoneum. P.196
P.197
P.198
P.199
P.200
Review Questions Multiple-Choice Questions Select the best answer for each question. 1. The following structures form the walls of the inguinal canal except which? (a) The conjoint tendon (b) The aponeurosis of the external oblique muscle (c) The internal oblique muscle (d) The lacunar ligament (e) The fascia transversalis View Answer1. D 2. The following statements concerning the walls of the inguinal canal are correct except which? (a) The inguinal ligament is made tense by flexing the hip joint. (b) The contracting internal oblique muscle reinforces the anterior wall of the canal in front of the weak deep inguinal ring. (c) The strong conjoint tendon reinforces the posterior wall of the canal behind the weak superficial inguinal ring. (d) Contraction of the arching fibers of the internal oblique and transversus abdominis muscles lowers the roof of the canal so that the canal is practically obliterated. (e) After birth, as the result of growth, the deep inguinal ring moves away from the superficial ring so that the canal becomes oblique and the two rings no longer lie opposite one another. View Answer2. A 3. In the female, the inguinal canal contains the following structures except which? (a) Ilioinguinal nerve (b) Remnant of the processus vaginalis (c) Round ligament of the uterus (d) Inferior epigastric artery (e) Lymph vessels from the fundus of the uterus View Answer3. D 4. The following statements concerning the spermatic cord are correct except which? (a) It extends from the deep inguinal ring to the scrotum. (b) It contains the testicular artery. (c) It is covered by five layers of spermatic fascia. (d) It contains the pampiniform plexus. (e) It contains lymph vessels that drain the testis. View Answer4. C. The spermatic cord is covered by three layers of spermatic fascia, which are derived from the three layers of the anterior abdominal wall. The external spermatic fascia is from the aponeurosis of the external oblique muscle, the cremasteric fascia is derived from the internal oblique muscle, and the internal spermatic fascia is formed from the fascia transversalis. 5. The following structures are present in the inguinal canal in the male except which? (a) Internal spermatic fascia (b) Genital branch of the genitofemoral nerve (c) Testicular vessels (d) Deep circumflex iliac artery (e) Ilioinguinal nerve View Answer5. D. The deep circumflex iliac artery is a branch of the external iliac artery and runs upward and laterally toward the anterior superior iliac spine away from the inguinal canal. 6. The following statements concerning the conjoint tendon are correct except which? (a) It is attached to the pubic crest and the pectineal line. (b) It is formed by the fusion of the aponeuroses of the transversus abdominis and internal oblique muscles. (c) It is attached medially to the linea alba. (d) It is continuous with the inguinal ligament. (e) It may bulge forward in a direct inguinal hernia. View Answer6. D 7. The following statements concerning an indirect inguinal hernia are correct except which? (a) It is the most common form of abdominal hernia. (b) The neck of the hernial sac lies medial to the inferior epigastric artery. (c) The sac is the remains of the processus vaginalis. (d) The hernial sac can extend into the scrotum. (e) At the superficial inguinal ring, the hernial sac lies above and medial to the pubic tubercle. View Answer7. B 8. To pass a needle into the cavity of the tunica vaginalis in the scrotum, the following structures have to be pierced except which? (a) Skin (b) Dartos muscle and Colles’ fascia (c) Tunica albuginea (d) Internal spermatic fascia (e) Cremasteric fascia View Answer8. C 9. The following statements are correct concerning the muscles forming the posterior abdominal wall except which? (a) The psoas major muscle has a fascial sheath that extends down into the thigh as far as the lesser trochanter of the femur. (b) The quadratus lumborum is covered anteriorly by fascia that forms the lateral arcuate ligament. (c) The iliacus muscle is innervated by the femoral nerve. (d) The transversus abdominis muscle forms part of the posterior abdominal wall. (e) The diaphragm does not contribute to the musculature on the posterior abdominal wall. View Answer9. E Matching Questions Match each structure listed below with the region on the anterior abdominal wall in which it is located. Each lettered answer may be used more than once. 10. Appendix 11. Gallbladder 12. Cecum 13. Left colic flexure (a) Right upper quadrant (b) Left lower quadrant (c) Right lower quadrant (d) None of the above View Answer10. C 11. A 12. C 13. D Match each structure listed below with the structure with which it is most closely associated. 14. External spermatic fascia 15. Round ligament of the uterus 16. Cremasteric fascia 17. Internal spermatic fascia 18. Deep inguinal ring (a) Internal oblique (b) Fascia transversalis (c) Gubernaculum (d) External oblique (e) None of the above View Answer14. D 15. C 16. A 17. B 18. B Match each structure listed below with the group of lymph nodes that drain it. 19. Testis 20. Skin of anterior abdominal wall below the level of the umbilicus 21. Epididymis 22. Skin of the scrotum (a) Anterior axillary lymph nodes (b) Para-aortic or lumbar lymph nodes (c) Superficial inguinal lymph nodes (d) External iliac nodes (e) None of the above View Answer19. B 20. C 21. B 22. C Read the case histories and select the best answer to the question following them. A 30-year-old man was seen in the emergency department with a stab wound in the right inguinal region. 23. Which of the following nerves supplies the skin of the inguinal region? (a) The 11th thoracic nerve (b) The 10th thoracic nerve (c) The 12th thoracic nerve (d) The first lumbar nerve (e) The femoral nerve View Answer23. D. The first lumbar nerve, represented by the iliohypogastric and ilioinguinal nerves, supply the skin just above the inguinal ligament and the symphysis pubis. Immediately after delivery, it was noted that a 7.5-lb male neonate had a large swelling on the anterior abdominal wall. The swelling consisted of a large sac, the walls of which were translucent and soft. The umbilical cord was attached to the apex of the sac, and the umbilical arteries and vein ran within its walls. 24. The following statements concerning this case are probably correct except which? (a) On closer examination it was possible to see within the sac coils of small intestine and the lower margin of the liver. (b) As the baby cried and started to swallow air, the sac became larger. (c) Failure of the formation of adequate head and tail folds of the embryonic disc causes a defect in the anterior abdominal wall in the umbilical region. (d) The defect in the anterior abdominal wall is filled with thin amnion, which forms the wall of the sac. (e) The condition is known as exomphalos or omphalocele. View Answer24. C. The defect is caused by a failure of the formation of adequate lateral folds in the umbilical region, which is filled in by amnion only. During the first 24 hours after birth, the wall of the sac becomes dry and opaque and may rupture, causing evisceration. Bacteria at once gain entrance to the peritoneal cavity, producing peritonitis. The sac of amnion should be surgically excised as soon as possible after birth and the contained viscera returned to the abdominal cavity. The defect in the anterior abdominal wall should then be closed. Footnotes *A common frustration for medical students is the inability to observe these rings as openings. One must remember that the internal spermatic fascia is attached to the margins of the deep inguinal ring and the external spermatic fascia is attached to the margins of the superficial inguinal ring so that the edges of the rings cannot be observed externally. Compare this arrangement with the openings for the fingers seen inside a glove with the absence of openings for the fingers when the glove is viewed from the outside. *The psoas minor is a small muscle with a long tendon that lies anterior to the psoas major. It is unimportant and is absent in 40% of patients.

Leave a Reply


Time limit is exhausted. Please reload the CAPTCHA.

Categories

apply_now Pepperstone Group Limited