The large bowl is about 1.5 m long, starting with the caecum and ending at the rectum. The caecum starts at the ileocaecal valve, which acts as a oneway valve to stop the reflux of bacteria from the colon into the small bowel.
The colon proceeds into the ascending colon, which passes up the right-hand side of the abdomen to the lower edge of the liver at the hepatic flexure. The transverse colon crosses from right to left across the abdomen, and extends from the hepatic to the splenic flexure. The endoscopist recognizes this area of the colon by its triangular shape. The descending colon extends from the splenic flexure to the sigmoid juncture - about 30 cm. It goes down the left side of the abdomen from the spleen to the left iliac crest. The sigmoid colon is S shaped and 40 cm long (Jackson, 1979). The rectum is a curved pouch, 9 cm long in young people, extending to 20 cm in adults. The rectum extends into the anal canal and is controlled by internal and external sphincters, which control defecation.
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