Anatomy of the abdominal viscera: Large intestine

The large intestine is a part of the digestive tract specialized in absorbing water from the residual digested food coming from the small intestines, while forming and storing feces until defecation occurs.

The large intestine or colon begins at the ileocecal junction, where it is continuous with the ileum, which is the final part of the small intestine.

There are three main features that distinguish the large intestine from the small intestine - besides the fact that the large intestine has a, well, larger caliber!

First, the large intestine has omental appendices, which present as fatty outgrowths covered by visceral peritoneum.

Second, there are the teniae coli, which are three strips of smooth muscle that run lengthwise from the base of the appendix through the colon and merge at the rectosigmoid junction to form a longitudinal layer around the rectum.

The third and final differentiating feature is that the large intestine has haustra, which are pouch-like bulges of the intestinal wall that form between the teniae when they contract.

The large intestine has several major components: the cecum, appendix, ascending, transverse and descending colon, sigmoid colon, rectum and anal canal.

The cecum is the first part of the large intestine and it receives the terminal ileum, which invaginates into the medial side of the cecum. The cecum lies in the right iliac fossa in the right lower quadrant of the abdomen, and it looks a bit like an intestinal pouch.

It is intraperitoneal, mobile, and doesn’t have its own mesentery. On its posteromedial wall, inferior to the ileocecal junction, the cecum has a blind-ended organ called the appendix, which can vary in length up to and over 10cm.