The Mechanism for Producing a Concentrated Urine Involves All of the Following

Question

The mechanism for producing a concentrated urine involves all of the following except
A) the secretion of antidiuretic hormone (ADH) by the posterior pituitary gland.
B) aquaporins being inserted into the membranes of the collecting duct cells.
C) a high concentration of NaCl in the interstitial fluid that surrounds the collecting ducts.
D) an increase in facultative water reabsorption.
E) obligatory water reabsorption in the proximal convoluted tubule.

Accepted Answer

Obligatory water reabsorption in the proximal convoluted tubule is not involved in the mechanism for producing a concentrated urine. The other choices are all involved in the mechanism. ADH secretion increases the permeability of the collecting ducts to water, aquaporins allow for water reabsorption, a high concentration of NaCl in the interstitial fluid creates an osmotic gradient for water reabsorption, and facultative water reabsorption occurs in response to ADH.