Question

A vein that collects blood from one network of capillaries and transports it directly to a second capillary network in another region of the body without returning to the heart is called
A. Coronary vein
B. Pulmonary vein
C. Portal vein
D. Carotid vein

Answer 1

Hint: Heart is thick, muscular, automatic pulsating and contractile organ which pumps the blood to various parts of the body through blood vessels. Blood vessels are narrow tubular vessels that conduct the blood.

Complete answer: Portal vein is a vein that collects the blood from some organs but supplies an intermediated organ before the heart. A portal vein and its branches collectively form a portal system.
In humans, there are two portal systems-
Hepatic portal system- Here, the liver acts as intermediate organs. In this, hepatic portal vein carries nutrients-rich deoxygenated blood from gut to liver so as to regulate the sugar level of blood and to change excess amino acids to urea.
Hypophyseal portal system- In this, pituitary acts as intermediate organs. It transports the releasing factors and inhibitory factors of hypothalamus to adenohypophysis to stimulate or inhibit the secretion of trophic hormones. Through this system hormones of hypothalamus reach the pituitary.
Renal portal system- It is absent in mammals but well developed in some fishes, all amphibians and lower reptiles. In this, veins from hind limbs and other posterior parts of the body join to form renal portal vein which branches into kidney. Here the excretory substances are filtered from blood. Femoral veins from the outer sides of hind limbs divide into the outer renal portal vein and inner pelvic vein. Sciatic vein from inner side of hind limbs join renal portal vein of its side. Blood is drained out of the kidney by the renal vein.
So, the correct answer is “Option C”.

Note: In humans, a network of arteries, arterioles, and capillaries carry the oxygenated blood entering the aorta to the tissues from whereas a system of veins, venules and vena cava collect the deoxygenated blood and emptied it into the right atrium.