The Descending Arm of the Loop of Henle is Permeable

Question

The descending arm of the loop of Henle is permeable to ____ but impermeable to ____.  
A) water; potassium ions
B) water; sodium ions
C) sodium ions; water
D) potassium ions; water
E) All choices are incorrect.

Accepted Answer

The descending arm of the loop of Henle is permeable to water but impermeable to sodium ions. This allows for the reabsorption of water from the filtrate and concentration of urine in the renal medulla.