Assertion: In the descending limb of loop of Henle, the urine is hypertonic, whereas in ascending limb of loop of Henle, the urine is hypotonic.
Reason: Descending limb is impermeable to sodium, while ascending limb is impermeable to water.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Explanation:
Descending limb of Henle is permeable to water but not to sodium. Consequently water moves out into interstitium and concentration of sodium in tubular filtrate rises making filtrate hypertonic. Ascending loop is impermeable to water but permeable to sodium and makes the filtrate hypotonic.