Assertion : In the descending limb of loop of Henle , the urine is hypertonic , while in ascending limb of loop of Henle , the urine is Hypotonic .
Reason : Descending limb is impermeable to Na' while ascending limb is impermeable to `H_(2)O`

Options

A. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
B. If both the assertion and the reason are true and the reason is not a correct explanation of the assertion
C. If the assertion is true but the reason is false
D. If both the assertion and reason are false

Answer

A

Explanation

(a) Descending limb is permeable to water but not to `Na^(+)` Consequently water moves out into interstitium and concentration of `Na^(+)` in tubular filtrate rises making the filtrate hypertonic. Ascending loop is impermeable ot water but permeable to Na^(+)` and makes the filtrate hypotonic.