Assertion : In the descending limb of loop of Henle the urine is hypotonic, while in ascending limb

Question

Assertion : In the descending limb of loop of Henle the urine is hypotonic, while in ascending limb of loop of Henle, the urine is hypertonic.\ Reason : Descending limb is permeable to water while ascending limb is permeable to $\mathrm{Na}^{+}$.\

Professor PC Thomas Classes · Answer

(d) : The descending limb of loop of Henle is permeable to water but almost impermeable to electrolytes. This concentrates the filtrate as it moves down. The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Therefore, as the concentrated filtrate pass upward, it gets diluted due to the passage of electrolytes to the medullary fluid.