Question

In nephron, transport of substances like sodium chloride and urea is facilitated by the special arrangement called counter current mechanism that comprises of

• A. Vasa Recta and collecting duct
• B. Ascending limb and collecting duct
• C. Henle's loop and Vasa Recta
• D. Henle's loop and glomerulus

Hint:

Henle's loop and Vasa Recta create a countercurrent gradient for efficient reabsorption.

Answer 1

The Correct Option is C

• Counter Current Mechanism: In the nephron, the countercurrent mechanism maintains the concentration gradient in the medulla, aiding reabsorption of water, sodium chloride, and urea.
• Component Analysis:
  • (1) Vasa Recta and collecting duct: Vasa Recta aids in maintaining the gradient, but the collecting duct is involved in water reabsorption, not the primary countercurrent pair. Incorrect.
  • (2) Ascending limb and collecting duct: The ascending limb (of Henle's loop) contributes to the mechanism, but the collecting duct is secondary. Incorrect.
  • (3) Henle's loop and Vasa Recta: Henle's loop (descending and ascending limbs) and Vasa Recta work together to create and maintain the osmotic gradient, facilitating countercurrent exchange. Correct.
  • (4) Henle's loop and glomerulus: The glomerulus filters blood, not part of the countercurrent mechanism. Incorrect.
• Conclusion: The correct answer is (3) Henle's loop and Vasa Recta, as they are the key components of the countercurrent mechanism.