Part of colon with no mesentery-
Ans. C. Ascending colona. The large intestine develops as a fully mesenteric organ. However, after the rotation of the gut tube in utero, large portions of it come to lie adherent to the retroperitoneum, which means that some parts of the colon are fixed within the retroperitoneum, and other parts are suspended by a mesentery within the peritoneal cavity. Those portions of the colon within the retroperitoneum are separated from other retroperitoneal structures by a thin layer of connective tissue which forms an avascular field during surgical dissection, but which offers little or no barrier to the spread of disease within the retroperitoneum.b. The caecum may be within the retroperitoneum, but more frequently is suspended by a short mesentery. The ascending colon is usually a retroperitoneal structure although the hepatic flexure may be suspended by a mesentery. The transverse colon emerges from the retroperitoneum on a rapidly elongating mesentery and lies, often freely mobile, in the upper abdomen.c. The transverse mesocolon shortens to the left of the upper abdomen and may become retroperitoneal at the splenic flexure. Occasionally the splenic flexure is suspended by a short mesentery. The descending colon is retroperitoneal usually to the level of the left iliac crest.d. As the colon enters the pelvis it becomes increasingly more mesenteric again at the origin of the sigmoid colon, although the overall length of the sigmoid mesentery is highly variable. The distal sigmoid colon lies on a rapidly shortening mesentery as it approaches the pelvis; by the level of the rectosigmoid junction the mesentery has all but disappeared, so that the rectum enters the pelvis as a retroperitoneal structure. The caecum and proximal ascending colon are often more mobile on a longer mesentery in the neonate and infant than they are in the adult.e. The mesorectum is enclosed by meso rectal fascia, a distinct covering derived from the visceral peritoneum that is also called the visceral fascia of the mesorectum, fascia propria of the rectum or the presacral wing of the hypogastric sheath. The fascia bounds the mesorectum posteriorly and thus lies anterior to the retro rectal space and the pre-sacral fascia. The meso rectal fascia is surrounded by a very thin layer of loose areolar tissue which separates it from the posterior and lateral walls of the true pelvis. Superiorly, the meso rectal fascia blends with the connective tissue bounding the sigmoid mesentery. Laterally, it extends around the rectum and mesorectum and becomes continuous with a denser condensation of fascia anteriorly. In males this anterior fascia is known as the rectovesical fascia of Denon Villiers, and in females it forms the fascia of the rectovaginal septum.
Transverse colon
Sigmoid colon
Ascending colon
Rectum
Large Intestine, Rectum, and Anal canal