Q4. Assertion: when ADH makes the collecting duct water-permeable, water can leave it in the medulla. Reason: the medullary interstitium has a high osmolarity, rising to about 1200 mOsmol L. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion: the interstitial gradient helps in an easy passage of water from the collecting tubule (NCERT pages 211–212).
Q5. Why is the arrangement in Henle’s loop called a counter current?
Because the filtrate flows in opposite directions in its two limbs (NCERT page 210).
Q6. Into which part of Henle’s loop do small amounts of urea enter?
The thin ascending segment in NCERT’s simplified urea-recycling account (page 211).