The vertical osmotic gradient in the kidney
A)is established and maintained by the countercurrent system
B)makes it possible to put out urine of variable concentration depending on the needs of the body by varying the degree of water permeability of the distal portions of the nephron
C)is found in the renal cortex
D)has characteristics a and b
E)has characteristics a and c

Question

Quizplus · Accepted Answer

The vertical osmotic gradient in the kidney is established and maintained by the countercurrent system, which involves the flow of filtrate in opposite directions in the nephron loop. This gradient makes it possible to put out urine of variable concentration depending on the needs of the body by varying the degree of water permeability of the distal portions of the nephron. Therefore, both characteristics A and B are true, making option D the correct answer. The osmotic gradient is not found in the renal cortex, which rules out options C and E as correct answers.

The Vertical Osmotic Gradient in the Kidney