n :  either of two arteries arising from the aorta and passing between the two layers of the mesentery to the intestine:  a  :  one that arises just above the bifurcation of the abdominal aorta into the common iliac arteries and supplies the left half of the transverse colon, the descending colon, the sigmoid colon, and most of the rectum - called also inferior mesenteric artery   b  :  a large artery that arises from the aorta just below the celiac artery at the level of the first lumbar vertebra and supplies the greater part of the small intestine, the cecum, the ascending colon, and the right half of the transverse colon - called also superior mesenteric artery  .
 
 
 
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