Aqueous humor is produced by the ciliary body epithelium. Which ion transport system is primarily responsible for the active secretion of aqueous humor?

• A Cl-/HCO3- exchanger
• B Ca2+ ATPase pump
• C H+/K+ ATPase pump
• D Na+/K+ ATPase pump ✓

Explanation

Aqueous humor is actively secreted by the non-pigmented ciliary epithelium primarily through the Na+/K+ ATPase pump located on the basolateral membrane of the non-pigmented epithelial cells. This creates an osmotic gradient driving sodium, bicarbonate, and water into the posterior chamber. Carbonic anhydrase also plays a role, but the primary driving force is Na+/K+ ATPase. The Cl-/HCO3- exchanger contributes but is not the primary system.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.