The Eyeball: Some Basic Concepts
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The eyeball consists of three concentrically arranged layers. The frontal one-sixth of the outer wall is formed by a transparent dome called the cornea. The back five-sixths of the outer wall of the eye is formed by a fibrous layer protective in function called the sclera. The sclera is quite thin at its front where the rectus muscles are inserted, and quite thick at its back, which explains why traumatic rupture of the eyeball is common there. It is richly supplied by sensory nerves (ophthalmic division of the trigeminal nerve); therefore its inflammation, or scleritis, is quite painful. The outer surface of the anterior sclera is covered by a thin layer of elastic tissue, called the episclera; this contains numerous blood vessels that nourish it.
KeywordsConcentrically arranged layers Cornea Sclera Uveal tract Iris Ciliary body Choroid Posterior scleral foramen Lamina cribrosa Anterior chamber Posterior chamber Vitreous chamber Ciliary processes Secretion Ultrafiltration Circulation of aqueous Intraocular pressure Microscopic outlet channels of aqueous Inflow of aqueous Outflow of aqueous
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