Where does the active secretion of aqueous primarily take place?

The active secretion of aqueous humor primarily occurs in the non-pigmented ciliary epithelium (NPCE). This aspect is crucial to understanding how the eye maintains intraocular pressure and provides nutrients to avascular structures such as the lens and cornea.

The NPCE is situated in the ciliary body of the eye and consists of two layers: the pigmented and non-pigmented epithelial cells. It is the non-pigmented layer that is primarily responsible for synthesizing and secreting aqueous humor. This process involves active transport mechanisms, where ions like sodium are actively secreted into the posterior chamber, which subsequently draws water osmotically into the aqueous humor.

The NPCE also plays a pivotal role in not just secretion but also in the composition of the aqueous humor, influencing its ionic concentration and nutrient content. The function of the NPCE is essential for maintaining vision and overall ocular health, as it ensures a continuous supply of fresh aqueous humor, which helps to maintain intraocular pressure and supports the metabolic needs of the eye.

Other structures mentioned, such as the corneal epithelium, lens capsule, and iris stroma, do not participate directly in the active secretion of aqueous humor. While the corneal epithelium