Question

Countercurrent multiplier creates a medullar osmotic gradient:

A By increasing concentration of aldosterone

B by utilizes vasa Recta to reabsorb water and solutes

C by increasing concentration of antidiuretic hormone’s

D by maintaining a difference in permeabilities between descending loop and ascending loop

Answer 1

Countercurrent mechanism help maintaining the medullary osmotic gradient and concentrating the urine .

It takes place in two ways:

(i) Countercurrent multiplier mechanism :takes place between descending loop and ascending loop of Henle by maintaining the difference in permeabilities between them.In descending loop water is transported ,it is impermeable to solutes . Na+ and Cl- are actively transported in ascending loop.

(ii) Countercurrent exchange mechanism: It takes place between Loop of Henle and vasa recta.

Thus D is correct .