The high osmolarity of the renal medulla is maintained by all of the following except
A) active transport of salt from the upper region of the ascending limb.
B) the spatial arrangement of juxtamedullary nephrons.
C) diffusion of urea from the collecting duct.
D) diffusion of salt from the descending limb of the loop of Henle.

Question

Quizplus · Accepted Answer

Diffusion of salt from the descending limb of the loop of Henle is not a mechanism that helps maintain the high osmolarity of the renal medulla. The ascending limb actively transports salt from the upper region, which creates a concentration gradient for the descending limb. Juxtamedullary nephrons are located close to the medulla and contribute to the osmotic gradient. Urea diffuses out of the collecting duct and contributes to the high osmolarity of the medulla.

The High Osmolarity of the Renal Medulla Is Maintained by All