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Chapter 29: Colon, Rectum, and Anus

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A 74-year-old man with biopsy-proven rectal adenocarcinoma is undergoing a low anterior resection. Which layers must be stapled through when resecting the distal portion of resection specimen?

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A. Mucosa, submucosa, circular muscle layer, longitudinal muscle layer, and serosa

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B. Mucosa, submucosa, longitudinal muscle layer, circular muscle layer, and serosa

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C. Mucosa, submucosa, longitudinal muscle layer, and circular muscle layer

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D. Mucosa, submucosa, circular muscle layer, and serosa

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Answer: C

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The wall of the colon and rectum are made of five separate layers: mucosa, submucosa, circular muscle layer, longitudinal muscle layer, and serosa. The mid and lower rectum lack serosa so this layer would not be stapled through if the surgeon were stapling through the mid or lower rectum. (See Schwartz 10th ed., p. 1176.)

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Which layer of muscle in the rectum joins together to form the internal anal sphincter?

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A. Circumferential muscle layer

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B. Longitudinal muscle layer

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C. Puborectalis muscle

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D. Inner smooth muscle layer

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Answer: D

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The inner smooth muscle joins to form the internal anal sphincter. The subcutaneous, superficial, and deep external sphincter surrounds it. The deep external anal sphincter is an extension of the puborectalis muscle. (See Schwartz 10th ed., p. 1176.)

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A 24-year-old woman with medically refractory ulcerative colitis decides to undergo a total colectomy. During this procedure, where would it be most appropriate to look for the inferior mesenteric vein in order to ligate it?

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A. Look for the inferior mesenteric artery; the veins of the colon usually parallel with the corresponding arteries.

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B. The inferior mesenteric artery can be ligated within the peritoneum, where it joins with the superior mesenteric artery.

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C. The inferior mesenteric vein is often ligated at the inferior edge of the pancreas, just below where it joins with the splenic vein.

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D. The inferior mesenteric vein will not be ligated for this procedure.

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Answer: C

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The inferior mesenteric vein does not run with the inferior mesenteric artery. Instead, it travels cranially in the retroperitoneum over the psoas and then posterior to the pancreas to join the splenic vein. The vein is often ligated at the inferior edge of the pancreas during a colectomy. (See Schwartz 10th ed., p. ...

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