What are the production dynamics of aqueous humor?

What are the production dynamics of aqueous humor?

• A. Aqueous humor is produced by diffusion through the cornea
• B. Aqueous humor is produced by the vitreous humor
• C. The choroid secretes aqueous humor
• D. Ciliary body epithelium actively secretes (80%) due to carbonic anhydrase; diffuse diffusion and ultrafiltration of plasma also occurs

Answer: (D)

The production of aqueous humor is an active secretory process carried out mainly by the nonpigmented ciliary epithelium of the ciliary body. These cells actively transport ions, especially via carbonic anhydrase–driven processes, to create an osmotic gradient that pulls water into the posterior chamber. This active secretion accounts for the majority of aqueous humor formation, and is why carbonic anhydrase inhibitors can reduce intraocular pressure. In addition to this active secretion, a portion forms by diffusion and ultrafiltration of plasma across the ciliary capillaries, contributing a smaller amount. The net result is fluid produced in the posterior chamber, flowing to the anterior chamber and exiting via the trabecular meshwork and uveoscleral pathways. The cornea does not produce aqueous humor, and the vitreous humor and choroid are not sources of its production.

The production of aqueous humor is an active secretory process carried out mainly by the nonpigmented ciliary epithelium of the ciliary body. These cells actively transport ions, especially via carbonic anhydrase–driven processes, to create an osmotic gradient that pulls water into the posterior chamber. This active secretion accounts for the majority of aqueous humor formation, and is why carbonic anhydrase inhibitors can reduce intraocular pressure. In addition to this active secretion, a portion forms by diffusion and ultrafiltration of plasma across the ciliary capillaries, contributing a smaller amount. The net result is fluid produced in the posterior chamber, flowing to the anterior chamber and exiting via the trabecular meshwork and uveoscleral pathways. The cornea does not produce aqueous humor, and the vitreous humor and choroid are not sources of its production.