Question

Vasa recta refers to
(A) Rectum region of insects.
(B) Blood capillaries in insects.
(C) A fine blood capillaries network of arterioles.
(D) A fine blood capillary network which runs parallel to Henle’s loop
(E) Juxtaglomerular complex of nephrons

Answer 1

Hint: Vasa recta is the blood capillaries which are responsible for maintaining the osmotic concentration in the urine. These groups of blood capillaries are found in the kidney.

Complete answer: Rectum region of insects are found in the large intestine. It is the part of digestive tract. It is responsible for removal of water from the faeces. That’s why it stores the faeces until it's ejected. Vasa recta and rectum are different things. That’s why “option A” is incorrect.
Blood capillaries are responsible for transporting the oxygen, carbon dioxide and food across the blood vessels and the tissue. Vasa recta are not found in the blood capillaries. That’s why “option B” is incorrect.
Vasa recta are fine blood capillaries of arterioles and venules. That’s why “Option C” is incorrect.
Vasa recta is the group of blood capillaries consisting of arterioles and venules. It runs parallel to the Henle’s loop. Henle’s loop consists of the ascending and descending loop of Henle. Vasa recta is responsible for the countercurrent mechanism.
Water is permeable to the descending loop of Henle and sodium ions are permeable to the descending loop of Henle.
Descending loop of Henle is impermeable to sodium ions and the ascending loop of Henle is impermeable to water.
In the countercurrent mechanism, NaCl is transported by the ascending limb of the loop of Henle and these sodium chloride ions are exchanged by the descending limb of vasa recta. Water from the descending loop of Henle is exchanged by the ascending limb of vasa recta. This leads to increase the osmolarity from 300 to 12000 mOsmol/L. In this way, it helps in concentrating the urine. That’s why “option D” is correct.
Juxtaglomerular complex is the part of nephron which is found in the kidney. It is the initial region of nephron. It filters the blood in the glomerulus to the proximal convoluted tubule region. That’s why “Option E” is incorrect.

So, the correct answer is option D.

Note: Counter current mechanism is the characteristic feature for concentrating the urine. It is found between vasa recta and the loop of Henle. Vasa recta is found in a parallel position to the loop of Henle so that association occurs between the vasa recta and Loop of Henle.