Sensory Notes - The Anatomy of the Eye In a normal eye,...

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1 The Anatomy of the Eye With every blink of the eyes the lids wash the cornea and conjunctiva with tears. They are formed by the lacrimal gland and the accessory lacrimal glands. A healthy tear is composed of 3 layers: the lipoid, aqueous, and mucoid. If there is any defect in these layers the integrity of the cornea may become compromised. Tears are secreted in response to reflex or emotional stimuli. The conjunctiva, a mucous membrane, provides a barrier to the external environment and nourishes the eye. The goblet cells of the conjunctiva secrete lubricating mucous. The sclera, AKA the white of the eye, is a dense, fibrous structure that comprises the posterior 5/6’s of the eye. It helps to maintain the shape of the eyeball and protects the intraocular contents from trauma. It may have a slightly blue tinge in young children, a dull white color in adults, and a slight yellow color in the elderly. Externally it is overlaid with conjunctiva, which is a thin, transparent, mucous membrane that contains fine blood vessels. The conjunctiva meets the cornea at the limbus on the outermost edge of the iris. The cornea, a transparent, avascular dome-like structure, forms the most anterior portion of the eyeball and is the main refracting surface of the eye. Behind the cornea lies the anterior chamber, filled with a continually replenished supply of clear aqueous humor, which nourishes the cornea. The aqueous humor is produced by the ciliary body, and its production is related to the IOP (10-21 mm Hg) The iris, or colored part of the eye, is a highly vascularized, pigmented collection of fibers surrounding the pupil. The pupil is a space that dilates and constricts in response to light. Normal pupils are round and constrict symmetrically when a bright light shines on them. Dilation and constriction are controlled by the sphincter and dilator pupilae muscles. The dilator muscles are controlled by the SNS and the sphincter muscles are controlled by the PNS. Directly behind the pupil and iris lies the lens, a colorless and almost completely transparent. It is avascular and has no nerve or pain fibers. The lens enables focusing for near vision and refocusing for distance vision. The ability to focus and refocus is called accommodation. The aqueous humor is anterior to the lens and the vitreous humor is posterior to the lens. All cells formed throughout life are retained by the lens, which makes the cell structure of the lens susceptible to the degenerative effects of aging. The posterior chamber is a small space between the vitreous and iris. Aqueous fluid is manufactured here by the ciliary body. It flows from the posterior chamber into the anterior chamber, from which it drains through the trabecular meshwork and the canal of Schlemm.
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This note was uploaded on 05/04/2008 for the course NURS 210 taught by Professor Jones-thomas during the Spring '08 term at Lady of the Lake.

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Sensory Notes - The Anatomy of the Eye In a normal eye,...

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