Assertion: The Henle's loop and vasa recta play a significant role in producing a concentrated urine.
Reason: The counter current arrangement of Henle's loop and vasa recta helps in this.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. if both assertion and reason are true but reason is not the correct explanation of assertion.
C. if assertion is true but reason is false
D. if both assertion and reason are false.

Answer

A

Explanation

Mammals have the ability to produce concentrated urine. The henle's loop and vasa recta play a significant role in this. The flow of filtrate in the two limbs of henle's loop is in opposite directions and thus forms a couter current. The flow of blood through the two limbs of vasa recta is also in a counter current pattern. The proximity between the henle's loop and vas recta, as well as the counter current in them help in maintaining and increasing osmolarity towards the inner medullary intersitium. presence of such interstitial gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine). Human kidneys can produce urine nearly four times concentrated than the inital filtrate formed.