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:
(terminal branch of the SMA) supplies last part of ileum, cecum, and appendix
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.
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.
^ Redaelli CA, Schilling MK, Buchler MW. Intraoperative laser Doppler flowmetry: a predictor of ischemic injury in acute mesenteric infarction. Dig Surg. 1998;15(1):55-9. PMID 9845564. Full Text.