Define a portal vein. Explain the functions of such a vein in our digestive tract.

Explanation

A vein which pours its blood to some intermediate organ like liver or kidney before taking it to heart is called portal vein. The absorbed nutrients from the small intestline are first brought to liver via hepatic portal vein. Here, excess unwanted substances are modified and the blood is then sent to heart via hepatic veins. So, heart is protected from loading with nutrients.