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 infor-
mation 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 notright side.
404.The answer is b.(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 seg-
ments 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 notinnervate the rectum.
405.The answer is d.(Moore and Dalley, pp 277– 280.)The colon nor-
mally 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 great-
est 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)arenotcorrect.
406.The answer is d.(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 pancreati-
coduodenal 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
526 Anatomy, Histology, and Cell Biology