What are the two epithelial layers of the ciliary body?

• A. Pigmented ciliary epithelium and nonpigmented ciliary epithelium.
• B. Nonpigmented ciliary epithelium and iris epithelium.
• C. Nonpigmented ciliary epithelium and pigmented ciliary epithelium.
• D. Pigmented ciliary epithelium and retinal pigment epithelium.

Answer: (C)

The ciliary body is lined by a double layer of epithelium: a pigmented ciliary epithelium and a nonpigmented ciliary epithelium. The pigmented layer is the outer layer facing the stroma and contains pigment; it is continuous with the retinal pigment epithelium at the ora serrata. The nonpigmented layer lies on the inner side, facing the posterior chamber, and is involved in active ion transport and aqueous humor production, working with the pigmented layer to move fluid into the posterior chamber. These two layers together form the ciliary epithelium that covers the ciliary processes and contributes to the blood-aqueous barrier. Structures like iris epithelium or retinal pigment epithelium are not part of the ciliary body’s dual epithelium. Therefore, the two epithelial layers are the pigmented and nonpigmented ciliary epithelium.