Inferior Mesenteric Vein
Superior Mesenteric Vein
The Portal vein is formed posterior to the neck of the pancreas by the confluence of the Superior Mesenteric and Splenic veins. The portal vein leaves the posterior body wall to enter the lesser omentum as one of the constituents of the porta hepatis. Important relationships of the three primary veins contributing to the formation of the portal vein: the superior mesenteric vein lies to the right of the superior mesenteric artery; the Inferior Mesenteric vein courses superior to the duodenojejunal junction to variably enter the splenic vein or the superior mesenteric vein; the splenic vein is embedded in the posterior aspect of the body and tail of the pancreas; the mesenteric veins lie anterior to the branches of the gonadal vessels crossing the posterior body wall.