Hepatic portal circulation (hepatic venous system) begins in the capillaries in the digestive system. It ends in the portal vein. Its directs all the blood from the gastrointestinal tract to the liver. Keep in mind that not all parts of the gastrointestinal tract are a part of the hepatic portal system. This blood that is circulated contains materials that the stomach and intestines absorbed. The hepatic lobules absorb, excrete, or convert all of the materials (both good and bad) from the portal blood.
A complication related to hepatic portal circulation is called portal hypertension and is usually caused by cirrhosis.