Portal venous system

The portal venous system includes all the vessels which collect venous blood from the abdominal part of the digestive tract (except for the lower part of the rectum) and the spleen, pancreas, and gallbladder. Blood from these organs enters the inferior surface of the liver through the large hepatic portal vein. 

One of the main functions of the portal venous system is providing the liver with the nutrient-rich blood from the gastrointestinal tract before distributing it to the rest of the body, as well as transporting toxins from the GI tract to the liver for the process of detoxification.

The main blood vessel of this system is the hepatic portal vein.