Question

A portal system is one which
(a) A vein starts from the organ and ends up at the heart.
(b) An artery breaks up in an organ and restarts by the union of its capillaries
(c) The blood from the gut is brought into the kidney before it is poured into the post caval
(d) A vein breaks up in an organ into capillaries and restarts by their union as a new vein from the same organ.

Answer 1

Hint: In animals with circulatory systems, a portal system is created when a bunch of capillaries connect with another bunch of capillaries with the help of veins. This network does not go through the heart.

Complete Answer:
The blood vessels that connect the bed of capillaries and the bed of capillaries are a part of the portal venous system.
Portal venous systems are relatively not found in the circulatory system of animals as all major beds of capillaries directly drain into veins of the circulatory system and then further drain into the heart. Most of the capillary beds do not drain into other capillary beds of the circulatory system. Portal systems are considered to be venous systems in the circulatory system because the blood vessels of the portal system are joined to the capillary bed by either a vein or several venules.

Therefore, the correct option is (d) A vein breaks up in an organ into capillaries and restarts by their union as a new vein from the same organ

Note:
There are many portal venous systems in the circulatory systems of animals. These portal venous systems include the:
1. Hepatic Portal System
2. Hypophyseal Portal System
3. Renal Portal System