Which statement concerning the loop of Henle of juxtamedullary nephrons is correct? A) The ascending limb of the loop of Henle is freely permeable to H₂O and NaCl. B) The filtrate is isotonic as it enters the loop of Henle, hypertonic at the tip of the loop, and hypotonic as it leaves the loop of Henle. C) The descending limb of the loop of Henle actively transports NaCl out of the tubule into the interstitial fluid.

Question

Quizplus · Accepted Answer

The descending limb of the loop of Henle is freely permeable to water but not to solutes, thus allowing water to passively diffuse out of the filtrate into the interstitial fluid, making the filtrate hypertonic as it descends. The ascending limb of the loop of Henle is impermeable to water but actively transports NaCl out of the tubule into the interstitial fluid, making the filtrate hypotonic as it ascends. Therefore, choice B is the only correct statement. Choice A is incorrect because the ascending limb is not permeable to urea. Choice C is incorrect because it is the ascending limb, not the descending limb, that actively transports NaCl out of the tubule.

Which Statement Concerning the Loop of Henle of Juxtamedullary Nephrons