Q4. Assertion: with ADH and a medullary gradient, the collecting duct can produce concentrated urine. Reason: ADH increases its water permeability, allowing water to move into the more concentrated interstitium. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion: NCERT says large amounts of water could be reabsorbed from the collecting duct to produce a concentrated urine (NCERT page 210).
Q5. Which segment selectively secretes hydrogen and potassium ions and NH to keep the sodium–potassium balance of the blood?
The distal convoluted tubule (NCERT page 209).
Q6. Where in the kidney does the collecting duct run?
From the cortex to the inner parts of the medulla (NCERT page 210).