- A Adding to medullary osmolarity, which aids water reabsorption from the duct
- B Reducing sodium reabsorption mainly along the nephron
- C Pumping water out of the collecting duct without any osmotic gradient
- D Diluting the medullary interstitium to limit water loss
Correct answer: A. Adding to medullary osmolarity, which aids water reabsorption from the duct
Explanation: Urea diffuses out of the collecting duct into the medullary interstitium and is recycled back into the loop of Henle, contributing to the high medullary osmolarity that drives water reabsorption from the collecting duct.
Concept context
Nitrogenous waste, kidney structure, urine formation in the nephron, and hormonal regulation of excretion.
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