What is called a portal system? Give names of the portal systems seen in a frog.

(N/A) portal system is a circulatory arrangement where blood collected from one organ or part of the body is transported to another organ through a vein before returning to the heart,instead of going directly to the heart.
In frogs,two types of portal systems are present:
$1$. Hepatic portal system: This is a special venous connection between the intestine and the liver.
$2$. Renal portal system: This is a special venous connection between the lower parts of the body (hind limbs) and the kidneys.