Return to the porta hepatis and again locate the hepatic portal vein, posterior to the common bile duct and the hepatic artery.

Follow this vein away from the liver to identify the three tributaries of the portal vein:

Figure 3-26
Tributaries at the beginning of the hepatic portal vein.

• The large splenic vein running from the spleen with the splenic artery
• The superior mesenteric vein draining most of the small intestine. (this vein was found in the mesentery with the superior mesenteric artery)
• The inferior mesenteric vein coming from the descending colon.

The inferior mesenteric vein may empty into either the splenic vein or the superior mesenteric vein, or it may join the portal vein at the junction of the splenic and superior mesenteric vein. The hepatic portal vein officially begins at this latter junction. The portal system has received tributaries from the rest of the organs of the digestive system. (Figure 3-26)