In simple words hepatic portal system can be considered as a shunting mechanism between the digestive tract and the blood circulation of the body. Normally blood from all body parts is directly carried back to heart by veins, but in this system the venous blood from the digestive tract is first taken to the liver and then to heart. It comprises of
a. Hepatic portal vein
b. Splenic vein
c. Superior and inferior mesenteric veins.
(i) Since liver is responsible for most of the metabolic functions, hepatic portal system takes most of the absorbed nutrients from the digestive tract first to the liver to process them accordingly. After that they are released in normal circulation by liver through hepatic vein.
(ii) This system is also responsible for proper action of various drugs on the body by activating them by liver before reaching to other organs.
(iii) It also helps in neutralizing many toxic materials absorbed from the digestive tract.
(iv) It helps in venous drainage from the pancreas and spleen also.