3. (Aeronautics) any structure corresponding to or resembling the keel of a ship, such as the central member along the bottom of an aircraft fuselage. 4. (Biology) biology a ridgelike part; carina. 5. a poetic word for ship.
Transverse colon and sigmoid colon. The transverse colon and the sigmoid colon have a mesentery (ie, transverse mesocolon and sigmoid mesocolon, respectively), but the ascending colon and descending colon are retroperitoneal, while the cecum is intraperitoneal but uses the mesentery of the ileum.
Inflammatory bowel disease such as ulcerative colitis and Crohn's disease may occur here. Diverticulitis, in which little outpouchings of bowel form and become inflamed, is more common in the sigmoid than any other part of the bowel. Small growths called polyps, as well as cancers, also favour this site. The good thing about investigating sigmoid disease is that this part of the colon isn't far from the outside world. It is easy to pass a rigid sigmoidoscope into the anus and get a decent view.