Eyelid

Here's a section through an eyelid, cut vertically, i.e., with the top of the lid at top left and looking at it from the side.

The inner surface of the lid is lined with conjunctival epithelium, specifically the tarsal conjunctiva. The outer surface is thin integument, with typical integumental adnexa, such as hairs and sebaceous glands. There's also a very large sebaceous gland on the inside, the so-called tarsal gland. If you've ever awakened the morning after a wild party with your eyes sort of glued shut by a crusty material, that's the secretion of this gland.

The conjunctival surface is moist. The secretions of its goblet cells, and tears produced elsewhere prevent the surface of the cornea from drying out. They also control bacterial proliferation. Since the cornea is isolated from the immune system and is constantly exposed to possible infection, this is a very important consideration.

Monkey eye; H&E stain; paraffin section, 40x

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