Superior mesenteric artery

In human anatomy, the superior mesenteric artery (SMA) arises from the anterior surface of the abdominal aorta, just inferior to the origin of the celiac trunk, and supplies the intestine from the lower part of the duodenum to the left colic flexure and the pancreas.

Location and path
It arises anterior to vertebra L1 in an adult. It is usually 1cm lower than the celiac trunk. It initially travels in an anterior/inferior direction, passing behind/under the neck of the pancreas and the splenic vein. Located under this portion of the superior mesenteric artery, between it and the aorta, are the following:
 * left renal vein - travels between the left kidney and the inferior vena cava (can be compressed by the SMA at this location, leading to the so-called nutcracker syndrome.
 * the third part of the duodenum, part of the small intestines
 * uncinate process of the pancreas - this is a small part of the pancreas that hooks around the SMA

The SMA typically runs to the left of the similarly named vein, the superior mesenteric vein. After passing the neck of the pancreas it starts giving off its branches.

Branches
The middle, right, and ileocecal branches anastomose with each other to form a marginal artery along the inner border of the colon. This artery is completed by branches of the left colic which is a branch of the inferior mesenteric artery.

Pathology

 * Compared to other vessels of similar size, the SMA is largely spared the effects of atherosclerosis. This is likely due to protective haemodynamic conditions
 * Occlusion of the SMA almost invariably leads to intestinal ischemia and often has devastating consequences; up to 80% of SMA occlusions lead to death.
 * The SMA can compress the left renal vein, leading to the nutcracker syndrome and/or the third (horizontal) part of the duodenum, leading to SMA syndrome.