Analyzing Henle's Loop Reabsorption Statements

This question requires identifying the correct statements regarding the reabsorption processes occurring within Henle's loop of the nephron.

Statement Evaluation

• Statement (a): "The descending limb of Henle's loop is permeable to water but almost impermeable to electrolytes."
• Statement (b): "Urine gets concentrated in Henle's loop."
• Statement (c): "Reabsorption of Na$^+$ and water takes place in Henle's loop."
• Statement (d): "Active or passive transport of electrolytes occurs in the ascending limb of Henle's loop."

Reasoning for Correctness

Let's evaluate each statement based on known renal physiology:

• Statement (b) is correct: Henle's loop, through the countercurrent multiplier mechanism, establishes an osmotic gradient in the renal medulla. This gradient facilitates water reabsorption from the descending limb and solute reabsorption in the ascending limb, leading to the concentration of the tubular fluid.
• Statement (c) is correct: Water is reabsorbed from the descending limb of the loop of Henle into the hypertonic medullary interstitium. Electrolytes, particularly Na$^+$ and Cl$^-$, are reabsorbed from the ascending limb (both thin and thick segments).
• Statement (d) is correct: The ascending limb exhibits differential permeability. The thin ascending limb allows passive diffusion of NaCl. The thick ascending limb actively transports NaCl out of the tubule into the medullary interstitium, contributing significantly to medullary hypertonicity.

Given that the correct answer combines statements (b), (c), and (d), we conclude these are the accurate descriptions for this question.

Conclusion

Based on the analysis, statements (b), (c), and (d) accurately describe the reabsorption processes and functions of Henle's loop. Therefore, the correct option includes only these three statements.