Question

Which of the following statements about the reabsorption process in Henle's loop are correct ?
(a) The descending limb of Henle's loop is permeable to water but almost impermeable to electrolytes.
(b) Urine gets concentrated in Henle's loop.
(c) Reabsorption of \(\text{Na}^+\) and water takes place in Henle's loop.
(d) Active or passive transport of electrolytes occurs in the ascending limb of Henle's loop.
Choose the correct answer from the options given below :

• A. (a), (b) and (d) only
• B. (a) and (b) only
• C. (b), (c) and (d) only
• D. (a), (b) and (c) only

Hint:

The loop of Henle plays a major role in establishing a high osmotic pressure in the kidney medulla. Remember: Descending limb is for water reabsorption (concentrating the urine); Ascending limb is for salt reabsorption (diluting the urine).

Answer 1

The Correct Option is A

Concept:

• Henle's loop is a hairpin-shaped part of the nephron with two functionally distinct limbs: itemize

• Descending limb: Permeable to water, but nearly impermeable to electrolytes. As filtrate moves down, water is reabsorbed, increasing the concentration of the filtrate.

• Ascending limb: Impermeable to water, but allows transport of electrolytes actively or passively.
itemize

Step 1: Analyze the correctness of each statement
Statement (a) is correct: The descending limb allows water to pass through but blocks electrolytes.
Statement (b) is correct: Reabsorption of water in the descending limb concentrates the medullary filtrate.
Statement (c) is incorrect: Reabsorption of water and \(\text{Na}^+\) occur in different, separate limbs of Henle's loop, not together in a single step.
Statement (d) is correct: Active or passive transport of electrolytes occurs in the water-impermeable ascending limb.

Step 2: Determine the correct combination
Since statements (a), (b), and (d) are correct, option (1) is the correct choice.