Answer to Dune

Question: Can you identify an intraperitoneal area of the colon that exhibits a mesentery?

Correct answer is D, the sigmoid colon. To answer this question correctly, you need to know that the caecum, transverse colon and sigmoid colon are considered intraperitoneal. Also, the stem of the question asked you to identify a part of the colon, not the small intestines. Hence, the only one of the three parts of the colon that can serve as a correct answer is the sigmoid colon. While one can argue that the identity of the small intestines is somewhat masked, their blood supply is not. The jejunal ileal branches are clear in the image. The same can be said for the parts of the colon. Here too, the left colic artery is clearly traveling to the left colic flexure and the descending colon, identifying them as retroperitoneal structures. In contrast, several sigmoidal branches are emerging form the IMA and traveling to the sigmoid colon, confirming its identity.

1.= Small intestines

2.= Small intestines

3.= Left colic flexure

4.= Descending colon

5.= Sigmoid colon

Answer to this question is based on material presented in lectures 3 of the Pelvis Lecture Series.