Inferior mesenteric artery
The inferior mesenteric artery (IMA) brings oxygenated blood to the large intestine, specifically to the top of the rectum and the left colic flexure. The upper part of the rectum should not be confused with the anus itself. The IMA serves the part of the rectum near the descending and sigmoid colons. As it runs its course, the IMA branches into the left colic and the superior rectal arteries, as well as the sigmoid branches. The IMA also has a similarly named venal counterpart, the inferior mesenteric vein. This vessel serves to drain deoxygenated blood from areas within the large intestine, and it feeds into the splenic vein. From there, blood eventually moves back to the heart, pulmonary artery, and lungs for a new supply of oxygen, as well as recirculation. There is one congenital condition that effects the inferior mesenteric artery. Some people are born with their kidneys fused. This alters the anatomy around the large intestines, and parts of the resulting "horseshoe kidney" is located below the IMA.
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In Depth: Inferior mesenteric artery