Question

We produce concentrated / dilute urine. This is facilitated by a special mechanism. Identify the mechanism.

• A. Reabsorption from PCT
• B. Reabsorption from Collecting Duct
• C. Reabsorption/ Secretion in DCT
• D. Counter current mechanism in Henle’s loop/ Vasa recta

Answer 1

The correct option is D

Counter current mechanism in Henle’s loop/ Vasa recta

Counter current mechanism helps to maintain a concentration gradient in the medullary interstitium. 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 initial filtrate formed. Mammals have the ability to produce a 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 counter current.