Question

The venous system of frog differs from that of a mammal in the presence of
A. Renal portal system
B. Hepatic portal system
C. Three superior vena cava
D. Hepatic vein

Answer 1

Hint: The renal portal system is a part of the circulatory system using which the blood is transported from the peripheral organs back into the guts.
It is characteristically found in living vertebrates apart from hagfishes, lampreys, and mammals.

Complete answer: The renal portal system is defined as a system of blood vessels by which veins carrying blood from different parts of the body is first to split into capillaries in another organ like kidney or liver then the blood is collected by another set of capillaries which unite to make another vein that carries blood to the guts.
The veins which carry blood to the capillary system in kidneys constitute the renal vascular system. The renal hepatic portal vein runs outside to the kidneys and receives blood from the dorso-lumbar vein and enters the kidney by a number of branches from the outer margin.
Inside the kidney, these veins break and rebreak to make capillaries.

So, the correct answer is option A. Renal portal system.

Note: The different parts of the body are furnished with mixed blood and this blood returns to the kidneys, it becomes more impure containing harmful substances like urea and other nitrogenous wastes.
The harmful substances are separated from the blood by kidneys and are passed outside within the sort of urine.