Question

The countercurrent arrangement of the two limbs of the loop of Henle becomes a multiplier of electrolyte concentration due to which other characteristic?

A. water permeability of the descending limb

B. water impermeability of the ascending limb

C. active transport of electrolytes out of the ascending limb

D. thickness of the ascending limb

Answer 1

Answer

The countercurrent multiplication process takes place in the kidneys where the osmotic gradient is generated using energy to reabsorb water from the tubular fluid and produce concentrated urine.

The main purpose of the loop of Henle is to reduce the water volume and solutes within the urine without causing any changes in the concentration. A hypertonic medulla is created by using countercurrent multiplier. The three parts involved in this process are

1) Thin descending limb

2) Thin ascending limb

3) Thick ascending limb

• The descending limb is permeable to water but not solutes. Thus, the osmolarity of peritubular space is increased, which draws more water out of descending limb.
• The thick ascending loop is not permeable to water but solutes like Na⁺, K⁺, and Cl^- are actively pumped out in the ratio 1:1:2. Therefore, the solute concentration of the fluid is higher in the ascending limb causing active transport of more electrolytes.

Therefore, the correct answer is option (C).