The Normal Eye - Eyelids and Conjunctiva
The primary function of the eyelids is to protect the eyes whilst keeping the cornea moist and free of dust and microscopic debris. Structurally, the eyelids consist of modified folds of skin grouped into a posterior lamella (conjunctiva and tarsal plate, which determines the shape of the eyelid) and an anterior lamella (muscle and skin).
The eyelids are complex tissues with protective and exocrine functions. For example, the secretion of the meibomian glands within the eyelids provides the important mucin component of tears.
The conjunctiva is essentially a mucous membrane that lines the under surface of each eyelid (palpebral conjunctiva) and covers the surface of the eyeball starting as far back as the upper fornix and ending at the margin of the cornea (bulbar conjunctiva).
The entire conjunctiva is richly supplied by blood vessels. The conjunctiva has a role in protecting the sclera and providing lubrication for the eye through the secretion of mucus from mucin glands and serous (accessory lacrimal) glands, which combine with lacrimal secretions to form tears. Although the large proportion of secretions is lacrimal fluid (aqueous component of tears) from the lacrimal glands, the conjunctival secretions are an important component.
The conjunctiva is a very important tissue for the continued well-being of the external eye. Unfortunately, there are many inflammatory conditions that the conjunctiva can be affected by.