What does the palpebral conjunctiva line?

The palpebral conjunctiva is a thin, transparent membrane that lines the underside of the eyelids. Its primary function is to provide a barrier that protects the eye and to assist in the secretion of mucus, which helps keep the eye lubricated. This tissue plays a significant role in maintaining eye health and function, facilitating smooth movement of the eyelids over the surface of the eyeball and contributing to the overall protective environment of the eye.

In contrast, the other options refer to different structures of the eye: the outer surface of the eye refers to the sclera and cornea, which are not lined by the palpebral conjunctiva; the edge of the cornea is not covered by this membrane but is instead the boundary between the cornea and the sclera; and the surface of the iris, a colored part of the eye, is not associated with the palpebral conjunctiva, as it lies deeper within the eye structure. Therefore, what the palpebral conjunctiva specifically lines is the underside of the eyelids.