Answer:
Inferior vena cava.
Explanation:
The hepatic portal system may be defined as the connection of different veins that carry blood from the different parts of the body to the like spleen, intestine, stomach to the liver.
The hepatic portal system helps in the detoxification of the blood. This system consists of the liver, hepatic arteries, hepatic veins, splenic vein and the mesentric vein. The inferior vena cava helps in the circulation of blood to the heart not to the hepatic portal system.
Thus, the answer is inferior vena cava.
