conjunctiva

The conjunctiva is a thin, transparent mucous membrane that covers the anterior surface of the sclera and lines the inner surfaces of the eyelids. It forms the conjunctival fornices at the junction of the bulbar and palpebral surfaces and continues onto the underside of the lids. It is divided into bulbar conjunctiva (over the sclera up to the corneal limbus), palpebral conjunctiva (lining of the eyelids), and the fornix conjunctiva (the upper and lower recesses). Histologically, it comprises non-keratinized, stratified squamous epithelium with goblet cells over a vascular stroma containing conjunctival-associated lymphoid tissue.

The conjunctiva receives blood from the anterior ciliary arteries, with venous drainage through conjunctival veins. Sensory innervation is provided mainly by branches of the nasociliary nerve (a branch of the ophthalmic division of the trigeminal nerve), enabling protective reflexes; autonomic innervation modulates tear production and vascular tone.

Functionally, the conjunctiva protects the ocular surface, contributes to tear film stability through goblet cell mucin secretion, and participates in immune defense via CALT. Its vascular and lymphoid components help respond to environmental agents while maintaining corneal clarity and surface lubrication.

Clinical relevance includes involvement in conjunctivitis of infectious or allergic origin, degenerative conditions such as pinguecula and pterygium, dry eye, and subconjunctival hemorrhage. Disorders of the conjunctiva can affect comfort, tear film homeostasis, and ocular surface health, necessitating evaluation by eye care professionals.