Inferior mesenteric artery
In human anatomy, the inferior mesenteric artery is the third main branch of the abdominal aorta and arises at the level of L3, supplying the large intestine from the distal transverse colon to the upper part of the anal canal. The regions supplied by the IMA are the descending colon, the sigmoid colon, and part of the rectum.
Structure
Origin
The IMA arises from the anterior aspect of the abdominal aorta.'The vertebral level of its origin is situated at L3,' below the origins of the two renal arteries, 3.8 cm above the aortic bifurcation, at the level of the umbilicus, and posterior to the inferior border of the horizontal part of the duodenum.''''''
Branches
Along its course, the IMA has the following branches:All these arterial branches further divide into arcades which then supply the colon at regular intervals.
Relations
The IMA is accompanied along its course by a similarly named vein, the inferior mesenteric vein, which drains into the splenic vein. The IMV drains to the portal vein and does therefore not fully mirror the course of the IMA.Distribution
Proximally, its territory of distribution overlaps with the middle colic artery, and therefore the superior mesenteric artery. The SMA and IMA anastomose via the marginal artery of the colon and via Riolan's arcade. The territory of distribution of the IMA is more or less equivalent to the embryonic hindgut.Clinical significance
The IMA and/or its branches must be resected for a left hemicolectomy.A horseshoe kidney, a common anomaly of the kidneys, will be positioned below the IMA.