Superior mesenteric artery

At a glance

English

Superior mesenteric artery

Latin (TA2)

Arteria mesenteries superior

System

Artery

Region

Trunk

Side

Single, on the midline

About the superior mesenteric artery

The superior mesenteric artery, often shortened to SMA, is the second of the three unpaired arteries that leave the front of the abdominal aorta for the digestive tract. It arises roughly a centimetre below the coeliac trunk, opposite the lower part of the first lumbar vertebra in adults. Its territory is the midgut: the small intestine from the lower half of the duodenum onwards, the caecum and appendix, the ascending colon and the proximal two-thirds or so of the colon's transverse part, together with part of the pancreas.

From its origin the artery heads forwards and downwards. It first lies behind the splenic vein and the pancreatic neck, then emerges below the neck and crosses in front of three structures that sit in the angle between it and the aorta: the left renal vein on its way to the inferior vena cava, the horizontal (third) part of the duodenum, and the uncinate process of the pancreas, which curls around behind it. The superior mesenteric vein runs beside it on the right. The artery then enters the root of the mesentery and curves down towards the right iliac fossa.

Its branches include the inferior pancreaticoduodenal artery, a row of jejunal and ileal arteries from its left side, and the middle colic, right colic and ileocolic arteries from its right side. The jejunal and ileal vessels join one another in arcades, which become more numerous and shorter towards the ileum. The colic branches link up along the inner edge of the colon to form the marginal artery, which is completed on the left by the left colic artery, which comes from the inferior mesenteric.

The SMA is relatively protected from atherosclerosis compared with arteries of similar size, perhaps because of the way blood flows through it. Sudden blockage, by an embolus or thrombus, starves the intestine of blood and is a surgical emergency. The narrow angle between the artery and the aorta also explains two compression syndromes: squeezing of the left renal vein, called nutcracker syndrome, and obstruction of the horizontal duodenum, known as superior mesenteric artery syndrome.

Course and supply

Arises from

The front of the abdominal aorta at the level of the first lumbar vertebra, about a centimetre below the coeliac trunk.

Ends in

After giving its jejunal, ileal and colic branches, its tapering end reaches the lower ileum in the right iliac fossa and joins the ileal branch of the ileocolic artery.

Supplies

Supplies the midgut: the lower duodenum, jejunum, ileum, caecum, appendix, ascending colon and greater part of the transverse colon, and part of the head of the pancreas.