Eyelid

A fold of tissue at the upper or lower edge of an eye socket. The eyelids are held in place by ligaments attached to the socket’s bony edges. They consist of thin plates of fibrous tissue (called tarsal plates) covered by muscle and a thin layer of skin. The inner layer is covered by an extension of the conjunctiva. Along the edge of each lid are two rows of eyelashes. Immediately behind the eyelashes are the openings of the ducts leading from the meibomian glands, which secrete the oily part of the tear film. The lids act as protective shutters, closing as a reflex action if anything approaches the eye. They also smear the tear film across the cornea.