Question

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

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

Answer 1

The correct option is A Counter current mechanism in Henle's loop/Vasa recta

Counter current mechanism

The mechanism which facilitates production of concentrated urine due to special positioning of Henle’s loop and vasa recta mediating counter current flow is known as counter current mechanism.


Counter current mechanism

The flow of filtrate in the two limbs of Henle’s loop and the flow of blood through the two limbs of vasa recta is in counter current pattern. This counter current flow helps in increasing osmolarity towards the inner medulla.

This helps in reabsorption of more water from the loop of Henle, further making the urine concentrated.

Final answer

(D) Counter current mechanism in Henle's loop/Vasa recta