Block 6 Anatomy Abdomen BRS Pretest W Xpl Prt 2

(Moore and Dalley, pp 284–285.) The spleen is one of the most frequently injured organs in the abdomen. This is especially so if the spleen was enlarged as a consequence of infectious mononucleosis making it more susceptible to rupture. Because it has an extensive blood supply, shock and death from bleeding into the peritoneal cavity can occur if a ruptured spleen is left untreated. The symptoms described above are consistent with blood loss most likely associated with a ruptured spleen.
None of the other abdominal organs, stomach (answer a), duodenum (answer b), pancreas (answer c), and kidney (answer d) are likely to cause the sudden drop in blood pressure.

(Moore and Dalley, p 285.) The patient in the scenario has infectious mononucleosis, a virus-induced illness, leading to swollen lymph nodes and spleen. The splenomegaly is evidenced by the very rounded contours of the organ. Infectious mononucleosis can exhibit liver involvement; however, the organ indicated is not the liver (not answers a, d, and e) but the spleen in the upper left hypochondrium. The bright organ between it and the vertebra is the left kidney. The liver is on the opposite side of the abdominal cavity. The stomach (answer c) is not seen.

Moore and Dalley, pp 213, 223–225.) A direct inguinal hernia protrudes through a space bounded superolaterally by the inferior epigastric vessels, medially by the rectus abdominus muscle, and superior to the inguinal ligament (Hesselbach’s triangle). The other statements (answers b, c, d, e) are true of an indirect inguinal hernia. A direct hernia traverses only the most medial part of the inguinal canal and is not covered by the most internal layers of spermatic cord fascia.

(Moore and Dalley, p 338.) An aortic aneurysm. This patient may have an abdominal aortic aneurysm. Risk factors for the development of an abdominal aortic aneurysm include hypertension, excessive weight and smoking. Males are about five times more likely to have an aortic aneurysm than females. About 5% of men over 60 years of age have abdominal aortic aneurysms. Ninety percent of the time abdominal aortic aneurysms develop inferior to the renal arteries. About two-third of the time they extend inferiorly to include one of the common iliac arteries. (What blood vessel comes off the aorta inferior to the renal arteries and superior to the bifurcation into common iliac arteries? Answer: gonadal and inferior mesenteric arteries.) Despite the retroperitoneal location of the abdominal aorta, the high-pressure in the vessel typically makes ruptures of abdominal aortic aneurysms fatal. Blood fills the peritoneal cavity and the individual bleeds to death. If discovered prior to rupture they are typically repaired if greater than about 5.5 cm in diameter. Currently they tend to be repaired intravascularly by placing a 6-inch Dacron tube with metalmesh cylinder into the aorta via the femoral artery. Anecdotally, abdominal aortic aneurysms have been known to rupture with straining, such as during defecation. None of the other conditions, a hiatal hernia (answer a), splenomegaly (answer b), cirrhosis of the liver (answer c), nor a horseshoe kidney (answer d) would normally pulsate.

(Moore and Dalley, p 284.) The splenic artery originates from the celiac trunk and courses tortuously along the posterior aspect of the pancreas. The left gastric artery (answer a) is a separate branch of the celiac trunk and courses along the lesser curvature of the stomach where it anastomoses with the right gastric artery (answer d), a branch of hepatic artery. The right gastro-omental (gastroepiploic) artery (answer e) is a branch of the gastroduodenal artery and courses along the greater curvature of the stomach. The superior mesenteric artery (answer b) is more inferior seen running to the right side of the patient.

. (Moore and Dalley pp 257–258, 330.) Enlargement of the gallbladder is a common complication of gallstone development. If the gallbladder enlarges enough and becomes inflamed then it can contact the inferior surface of the diaphragm, leading to right-sided shoulder/neck pain. The liver, if inflamed, would also produce right-sided shoulder/neck pain [thus not (answer a)]. The pancreas (answer c) is mainly a midline organ that is retroperitoneal, thus even when infected and inflamed it is unlikely to contact the center of the diaphragm (that portion which carries afferent information back to cervical levels of the spinal cord). An enlarged spleen could cause left sided shoulder/neck pain [thus not (answer d)]. Normally the appendix (answer e) is too inferior to contact the diaphragm and would cause pain on the left not right side.

(Moore and Dalley, pp 223–225.) Most indirect inguinal hernias are congenital [present at birth; thus not (answers d and e)]. Indirect inguinal hernias recapitulate the passage of the testis through the abdominal wall, and as such, originate lateral to the inferior epigastric vessels and reopen the process vaginalis if it had ever separated from the peritoneal cavity. Large indirect inguinal hernias need to be repaired to prevent intestinal organs from being strangulated within the inguinal canal and the process vaginalis needs to be closed to prevent abdominal peritoneal fluid from accumulating in the scrotum, causing swelling upon increased intraabdominal pressure. Only about 1 in 20 inguinal hernias occur in females [thus not (answers a and b)]; 95% are within males.

Moore and Dalley, pp 63–64, 320.) The adrenal medulla is innervated from thoracic levels of the spinal cord mediated by preganglionic sympathetic nerve fibers traveling in the lesser and least splanchnic nerves, with some contribution from the greater splanchnic and lumbar splanchnic nerves [thus not (answer b)]. Because both the adrenal medulla and postganglionic sympathetic neurons are adrenergic and derived from neural crest tissue, the homology of the chromaffin cells and postganglionic sympathetic neurons is apparent. There appears to be no parasympathetic innervation (answers c and d) to the adrenal medulla or cortex. There is no somatic (answer e) innervation by the adrenal medulla, by definition a visceral organ.

Sadler, pp 229–231.) The kidney forms in three stages. The pronephric, metanephric, and mesonephric kidneys all form from the urogenital ridge, an extension of intermediate mesoderm into the coelomic cavity. Mesoderm derived from the somites (somatic; answer a) gives rise to components of the axial skeleton and associated muscle and connective tissues. Splanchnic lateral plate mesoderm (answer c) gives rise to the smooth muscle and connective tissue tunics of the abdominal viscera. Somatic lateral plate mesoderm (answer d) contributes substantially to the skeleton, connective tissue, and muscle mass of the appendages. Neural crest (answer e) forms the sensory and sympathetic chain ganglia and other structures.

Moore and Dalley, pp 316–318.) The venous drainage from each adrenal gland tends to be through a single vein. The left adrenal gland usually drains into the left renal vein superior [thus not (answers a and b)] to the point where the gonadal vein enters the left renal vein. The left adrenal vein usually anastomoses with the hemiazygos vein and may provide an important route of collateral venous return. Left inferior phrenic vein (answer c) and superior mesenteric vein (answer e) has no connections with adrenal veins. The right adrenal gland usually drains directly into the inferior vena cava.

(Moore and Dalley, pp 277– 280.) The colon normally has two regions where it is retroperitoneal: the ascending and descending colon. There are also two normal points of flexure: the hepatic (right) and splenic (left) flexures. Therefore, the sigmoid colon, splenic flexure, and hepatic flexure are the regions where the gastroenterologist has the greatest difficulty passing the fiberoptic scope, and thus have the greatest risk of bowel perforation. This is perhaps most easily visualized by looking at Fig. 2.44 on p 278 of Moore & Dalley. Other answers (answers a, b, c, and e) are not correct.

(Moore and Dalley, pp 284–287.) The body and tail of the pancreas receive most of their blood supply from the splenic artery via the great pancreatic, dorsal pancreatic, and caudal pancreatic arteries. The head of the pancreas is supplied by the superior pancreaticoduodenal artery that arises from the gastroduodenal branch of the common hepatic artery. In addition, the pancreatic head is supplied by the inferior pancreaticoduodenal arteries that arise from the superior mesenteric artery. The chief supply to the left side of the gastric (answer c) fundus is from the splenic artery via the short gastric branches. The splenic artery also gives rise to the left gastro-omental artery that runs along the greater curvature to anastomose with the right gastro-omental branch that arises indirectly from the common hepatic artery. None of the other arteries, common hepatic (answer a), the inferior phrenic (answer b), and superior mesenteric (answer e) are close to the pancreas.

(Moore and Dalley, p 284.) Structure 20 is the common hepatic artery. The celiac [18; (answer a)] artery (trunk) gives off the splenic [19; (answer d)] artery (to the patient’s left) and the common hepatic [20; (answer b)] artery (to the patient’s right). Other labeled structures are as follows: 17, right adrenal gland; 21, portal vein; and 22, left adrenal gland. The crus of diaphragm (answer c) is seen covering each side of the abdominal aorta. The superior mesenteric artery (answer e) is not seen in this image and would be further inferior with the abdomen.

(Moore and Dalley, p 276.) Sensation produced by distention of the rectum travels along the pelvic splanchnic nerves to sacral levels S2–S4. Fecal continence is affected by nerves from the S2–S4 segments of the spinal cord. The principal effector, the puborectalis portion of the levator ani muscle, is innervated by somatic twigs from the sacral plexus. The external anal sphincter is controlled by the pudendal nerve (answer c), which also carries pain sensation associated with external hemorrhoids. The lumbar (answer a) and sacral (answer d) sympathetic chain would provide motor innervation to the rectum. The vagus (answer e) nerve does not innervate the rectum.

(Moore and Dalley, pp 250, 252.) This patient has a sliding hiatal hernia. Sliding hiatal hernias are more common than paraesophageal hiatal hernias (answer b). Sliding hiatal hernias are generally acquired in middle age and lead to chest pain, difficulty swallowing food and acid reflux. A congenital Bochdalek hernia (answer c) is unlikely since they usually allow a portion of the small intestine to enter the left pleural cavity and are a medical emergency in newborns. Neither pylorospasm (answer d) nor congenital hypertrophic pyloric stenosis (answer e) is likely since barium is reaching the small intestine.

. (Moore and Dalley, pp 212, 298, 300.) The findings are consistent with hepatomegaly. There are two pieces of physical evidence that point towards an enlarged liver as being the likely cause of the physical findings. While the liver lies in the upper right quadrant of the abdomen it is generally fairly well covered by the costal margin. Enlargement of the liver can be caused by chronic alcohol consumption. In addition, the prominent veins on her anterior abdominal wall (called caput medusae) may be a site of portal hypertension as blood backs up within the hepatic portal system and uses alternative routes, rather than through the liver, to return to the systemic circulatory system. In addition to prominent abdominal veins, portal hypertension may also cause esophageal varices and hemorrhoids. Splenomegaly (answer a) would be palpated on the left side. While both the gall bladder and appendix are on the right side of the abdomen, both cholecystitis (answer d) and appendicitis (answer c) should result in abdominal pain, which is absent in this patient. An abdominal aortic aneurysm (answer e) would normally appear in the midline and pulsate.

(Moore and Dalley, pp 276, 279–281.) The major artery that is going to be reconnected is the marginal artery and the superior and inferior mesenteric lymph nodes will be collected. About a foot long section of the splenic flexure along with the marginal artery (of Drummond) and vein, paracolic lymph nodes and adjacent mesentery would all be surgically removed. The splenic flexure receives blood from the marginal artery. Blood from the splenic flexure portion of the marginal artery comes from both the middle colic artery, which is a branch off the superior mesenteric artery and from the left colic, which is a branch of the inferior mesenteric artery. Thus, it is essential to collect lymph nodes from the base of both the superior mesenteric and inferior mesenteric arteries. Neither the splenic artery (answers b and c) nor aorta (answer a) would be sectioned. The sigmoid artery (answer e) serves the sigmoid colon and would remain intact.

Moore and Dalley, pp 311–312.) The newly transplanted kidney will be placed in the iliac fossa in the greater pelvis, attached to branched iliac vessels and the ureter connected directly to the bladder. Generally unless the kidneys are infected the host kidneys are left in place [thus not (answers a and b)]. The newly transplanted kidney is placed in the greater pelvis and connected to the iliac vessels [thus not (answer c)]. Often the internal iliac artery is connected to the renal arteries. Normally, anastomotic connections across the midline from the opposite internal iliac artery keep pelvic organs with enough blood to maintain proper function. The transplanted renal vein is often connected to, the external iliac vein, since it is typically larger and thus easier to establish anastomoses.

(Moore and Dalley, pp 326–329.) The diaphragm possesses three principal hiatuses shown in the diagram accompanying the question: the hiatus for the inferior vena cava (answer a), the esophageal hiatus (answer c), and the aortic hiatus (answer e). Potential diaphragmatic developmental defects include the foramen of Morgagni (answer b), just lateral to the xiphoid attachment of the diaphragm, and the pleuroperitoneal canal of Bochdalek (answer d), which is the most common site for congenital hernias. The inferior vena cava and frequently small branches of the right phrenic nerve pass through a hiatus (A) slightly to the right of the midline at the T8 level. The left phrenic nerve usually passes through the central tendon of the diaphragm on the left side to innervate the left hemidiaphragm from below. The esophageal hiatus (C) just to the left of the midline at the T10 level transmits the esophagus, the left and right vagus nerves, and the esophageal branches of the left gastric artery and vein. An acquired hiatal hernia usually is the consequence of a short esophagus or of a weakened esophageal hiatus. The two diaphragmatic crura are joined superiorly by the median arcuate ligament to form an opening (E) at the T12 level. The aortic hiatus transmits the aorta, thoracic duct, and a continuation of the azygos vein into the abdomen. The splanchnic nerves penetrate the crura on each side of the aortic hiatus to reach the abdomen.

(Moore and Dalley, pp 277, 257–258.) Volvulus (twisting of the GI tract on itself) which limits movement of material within the lumen and may compromise blood flow occurs most frequently with the jejunum and ileum and the sigmoid colon. These are intraperitoneal segments of the GI tract. The jejunum and ileum are both midgut derivatives and thus refer pain to the periumbilical region [thus not (answer b)]. The sigmoid colon is the most mobile portion of the large bowel and is derived from the hindgut and tends to refer pain to the suprapubic region (especially on the left side) [thus not answers c and d)]. The duodenum (answer a) is retroperitoneal and generally does not undergo volvulus.

(Moore and Dalley, pp 280, 306, 450–451.) Potential causes of blood in the stool (hematochezia) include diverticular disease, internal hemorrhoids, and colorectal cancer [thus not (answers a and b)]. Diverticular disease mainly affects middle age and older adults. It is an outpocketing of the lining of the colon, occurring most frequently in the sigmoid colon. Diverticular disease may be caused by lack of fiber in the diet. If the diverticula get large, they may rupture blood vessels and bleed. Internal hemorrhoids are dilated (varicose) veins that develop above the pectinate line within the internal rectal venous plexus. They can develop as a consequence of hepatic cirrhosis, which could cause portal hypertension as blood resistance within the liver increases. Venous blood within the portal system backflows down the superior rectal veins and into the inferior rectal veins, that are part of the systemic venous system that does not have to pass through the liver. Most colorectal cancers initially develop as polyps, which continue to grow and differentiate and in later stages develop increased vascularity and bleed. External hemorrhoids and fissures may result in blood in the stool, but are generally painful [thus not (answers c and d)].

(Moore and Dalley, pp 321–324.) The diffuse central abdominal pain in the patient presented is probably referred pain from the loop of small bowel incarcerated within the herniated peritoneal sac that then undergoes ischemic necrosis. Compression of the bowel results in compromise of the blood supply and subsequent ischemic necrosis [thus not (answer e)]. The visceral afferent fibers from the distal small bowel travel along the blood vessels to reach the superior mesenteric plexus and lesser splanchnic nerves, which they follow to the T10–T11 levels of the spinal cord. The pain, therefore, is referred to (appears as if originating from) the T10–T11 dermatomes, which supply the umbilical region. Because the gut develops as a midline structure, visceral pain tends to be centrally located regardless of the adult location of any particular region of the gut. As a result of dilation (answer c) of the inguinal canal by the hernial sac, however, the patient also experiences localized somatic pain mediated by the iliohypogastric, ilioinguinal (answer b), and genitofemoral nerves (answer a), but this was not what
the question asked.

(Moore and Dalley, pp 306, 445, 450–451.) A, b, and c. The rectum receives blood from three different arteries, which come from three different major branches: superior rectal artery off the inferior mesenteric artery; middle rectal artery off the internal iliac artery, and inferior rectal artery off the internal pudendal artery (Moore & Dalley, p 445). Thus none of the other answers are complete (answers a, b, c, and d). There are also three sets of veins: superior rectal veins, which drain into the hepatic portal system; middle rectal veins, which drain into the internal iliac veins (part of the systemic venous system); and inferior rectal veins, which drain into internal pudendal veins (also part of the systemic venous system). Because the internal rectal venous plexus is a potential site of portal-systemic anastomoses, internal hemorrhoids may be an indication of liver pathology.