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Structure of the conjunctiva (Fig. 4.1): The conjunctiva is a thin vascularmucous membrane that normally of shiny appearance. It forms the conjunc-tival sac together with the surface of the cornea. The bulbar conjunctiva is loosely attached to the sclera and is more closely attached to the limbus of the cornea. There the conjunctival epithelium fuses with the corneal epithelium. The palpebral conjunctiva lines the inner surface of the eyelid and is firmly attached to the tarsus. The loose palpebral conjunctiva forms a fold in the conjunctival fornix, where it joins the bulbar conjunctiva. A half-moon-shaped fold of mucous membrane, the plica semilunaris, is located in the medial corner of the palpebral fissure. This borders on the lacrimal caruncle, which contains hairs and sebaceous glands.
Function of the conjunctival sac: The conjunctival sac has three main tasks:
1. Motility of the eyeball.The loose connection between the bulbar conjunc-tiva and the sclera and the “spare” conjunctival tissue in the fornices allow the eyeball to move freely in every direction of gaze.
2. Articulating layer.The surface of the conjunctiva is smooth and moist toallow the mucous membranes to glide easily and painlessly across each other. The tear film acts as a lubricant.
3. Protective function.The conjunctiva must be able to protect againstpathogens. Follicle-like aggregations of lymphocytes and plasma cells (the lymph nodes of the eye) are located beneath the palpebral conjunctiva and in the fornices. Antibacterial substances, immunoglobulins, interferon, and prostaglandins help protect the eye.
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