The Hepatic Portal Vein
This is the major route of venous drainage from the gastrointestinal organs, the pancreas, the spleen and the rectum. It arises from a capillary bed in the mesojejunum and terminates in the hepatic capillary bed.
There are three main tributaries corresponding to the three arteries that supply the gastrointestinal organs:• Gastrosplenic tributary draining the intra-abdominal oesophagus, the stomach, early duodenum, pancreas and the spleen. It is about 5 mm in diameter.
• Cranial mesenteric vein draining the small intestine via the jejunal veins that accompany the corresponding arteries.
• Caudal mesenteric vein originating as the cranial rectal vein, which then gathers several tributaries, namely the ileocaecocolic, common colic, left and right colic veins.
The distal rectum and anus are drained via the paired internal iliac veins, which then drain to the caudal vena cava via the common iliac veins.
The hepatic portal vein enters the liver at the porta together with hepatic arteries, nerves and the bile duct; this gateway to the liver is termed the hilus (see Section 7.2).
9.3