Anatomy - Laparoscopic colectomy with ileorectostomy - general and visceral surgery

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  • Colon

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    The colon is divided into the cecum with vermiform appendix, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.
    The colon originates in the right iliac fossa and merges with the rectum at the level of the second sacral vertebra. The colon frames the loops of small bowel in inverted U-fashion.

    Blood supply

    Ascending and transverse colon are supplied by the ileocolic, right colic, and middle colic arteries, which originate on the right side of the superior mesenteric artery. To its right, the middle colic artery communicates with a branch of the right colic artery, and to its left with a branch of the left colic artery.
    The descending and sigmoid colon and most of the rectum receive its blood supply from the inferior mesenteric artery via the left colic, sigmoid, and superior rectal arteries.

    Anastomosis of Riolan

    This anastomosis between the middle and left colic arteries, i.e., between the superior and inferior mesenteric arteries, is not always present. It can provide collateral arterial blood supply to the colon if one of these two mesenteric vessels is occluded.

    Overview Arterial blood supply to the colon

    Veins

    The arteries are paralleled by the homonymous veins draining the blood into the superior and inferior mesenteric veins. Both vessels empty into the hepatic

  • Colon segments

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    The large bowel differs from the small bowel in that it has taeniae coli, haustra and epiploic appendages.

    There are three taeniae coli, i.e., the free (libera), epiploic and mesocolic taeniae. These are strips of reinforced longitudinal muscle about 1 cm wide. Only the free taenia is fully exposed. Haustra are sacculations presenting the length of the large intestine because of peristaltic contraction of the colon. Between the haustra, the intestinal wall condenses into transverse crescent folds protruding into the intestinal lumen. These are known as semilunar folds because of their shape. The epiploic appendages are fatty appendages of the free taenia.

    Cecum and vermiform appendix

    The cecum in the right iliac fossa is the commencement of the large intestine and is the portion located below a transverse line passing just above the ileocecal valve. Most often the cecum is intraperitoneal but may also cling to9 the posterior abdominal wall to a greater or lesser extent due to secondary adhesions.
    The intraperitoneal cul-de-sac tubular vermiform appendix arises from the medial wall of the cecum directly caudad of the ileocecal valve in the taenia libera.

    Ascending colon

    The cecum merges with the ascending colon superior to the ileocecal valve. The ascending colon ascends to the right colic flexure, which is usually located between the right inferior pole of kidney and the inferior aspect of the right lobe of liver, where it forms the colic impression. It is covered on all sides with peritoneum, except its posterior surface and is bound by areolar tissue to the posterior abdominal wall.

    Transverse colon

    The transverse colon begins at the hepatic flexure and varies greatly in length. While attached to the posterior abdominal wall by the transverse mesocolon, it is also mobile. There are peritoneal connections to neighboring organs: The hepatocolic ligament to the liver and the gastrocolic ligament to the stomach or large gastric curvature. The transverse colon lies intraperitoneally.

    Descending colon

    At the splenic flexure inferior to the dome-shaped diaphragm, the transverse colon joins the descending colon at an acute angle. This segment is located retroperitoneally once again.

    Sigmoid

    The descending colon joins the sigmoid colon at the level of the left iliac fossa. This S-shaped portion has a free mesentery, the sigmoid mesocolon, and becomes continuous with the rectum at the level of the second sacral vertebra.

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