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Veins which return blood from the intestines; the inferior mesenteric vein empties into the splenic vein, the superior mesenteric vein joins the splenic vein to form the portal vein.

Are two in number, and belong to the vena porta. They are distinguished into, 1. The Superior mesenteric or mesaraic or great mesaraic. This trunk received, from above to below and on the right side, the three venae colicae dextrae and the Gastroepiploica dextra. Into its left side, the veins of the small intestine open. It passes in front of the transverse portion of the duodenum; and, behind the pancreas, unites with splenic vein to concur in the formation of the vena porta. The inferior or lesser mesenteric vein corresponds to the artery of the same name, and opens into the splenic, near the union of that vein with the superior mesenteric, and behind the pancreas.