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

Step 1: Understand the structure.
Henle's loop is the hairpin part of the nephron with a descending limb and an ascending limb that behave very differently.
Step 2: Test statement (a).
The descending limb is permeable to water but almost impermeable to electrolytes. This is correct.
Step 3: Test statement (b).
As water leaves the descending limb, the filtrate left behind becomes more concentrated in the medulla, so urine getting concentrated here is correct.
Step 4: Test statement (c).
Water and $\text{Na}^+$ are reabsorbed in different limbs, water mainly from the descending limb and electrolytes from the ascending limb, not together in one step. So this statement is incorrect.
Step 5: Test statement (d).
The ascending limb is impermeable to water but moves electrolytes out by active or passive transport. This is correct.
Step 6: Combine the correct ones.
Correct statements are (a), (b), and (d), which is option (1).
\[ \boxed{\text{(a), (b) and (d) only}} \]