In frogs, a special venous connection carries blood from the lower parts of the body to the kidneys before it returns to the heart. This specific venous connection is known as the:

Step-by-step solution

In frogs, there are special venous connections present in the circulatory system. The venous connection that carries blood from the lower parts of the body to the kidneys is called the renal portal system. The hepatic portal system connects the liver and the intestine. The pulmocutaneous vein and hepatic vein are other blood vessels but do not form the portal system between the lower body and kidneys. Answer: Renal portal system