SMA / IMA
(SMA – Ryan p.168, 172f, 173; IMA Ryan p.173f, 174f, 174)
Arterial supply of the small intestine
- The entire small intestine is supplied by the superior mesenteric artery, which arises from the aorta at the L1 vertebral level.
- Jejunal and ilea branches arise from the left of the main trunk.
- These branches link with one another in a series of arcades, which are usually single in the jejunum but number up to 5 in the distal ileum.
- The arteries that enter the intestinal wall – the vasa recta – are end arteries.
The arterial supply of the colon
- The part of the colon derived from the midgut (i.e. caecum to the midtransverse colon) is supplied by the superior mesenteric artery as follows:
- The ileocolic artery (the lowest right-sided branch of the main trunk of the superior mesenteric artery) supplies the caecum, appendix and the beginning of the ascending colon
- The right colic artery (arising about the midway down right side of the SMA, occasionally from a common trunk with ileocolic artery) supplies the remainder of the ascending colon
- The middle colic artery (arising from SMA just below pancreas) supplies the transverse colon to its midpoint
- The inferior mesenteric artery supplies the colon as far as the upper rectum as follows:
- The left colic artery to the descending colon;
- The sigmoid artery to the sigmoid colon; and
- The superior rectal (superior haemorrhoidal) artery to the upper rectum
Each of these vessels anastomoses with its neighbor, forming a marginal artery (of Drummond) close to the colon. The vessels that enter the bowel are, however, end arteries
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