In the large intestine, one distinguishes the cecum with the vermiform appendix, the ascending colon, transverse colon, descending colon, sigmoid colon, and the rectum.
The colon begins in the right iliac fossa and transitions into the rectum at the level of the second sacral vertebra. The colon forms a frame around the loops of the small intestine.
Vessels
The arterial supply for the ascending and transverse colon is provided by the ileocolic artery, right colic artery, and middle colic artery, which originate on the right side of the superior mesenteric artery. The middle colic artery connects to the right with a branch of the right colic artery, to the left with a branch of the left colic artery.
The descending and sigmoid colon and the majority of the rectum are supplied by the inferior mesenteric artery through the left colic artery, sigmoid arteries, and superior rectal artery.
Riolan's Anastomosis
It is an anastomosis that does not regularly occur between the middle colic artery and the left colic artery, ultimately between the superior and inferior mesenteric arteries. It can ensure collateral circulation of the colon in the event of an occlusion of one of the mesenteric vessels.
Veins
Parallel to the arteries run the veins of the same name, which drain the blood into the superior and inferior mesenteric veins. Both vessels empty into the portal vein of the liver.