Doncouse_Jeremy_Week15

Doncouse_Jeremy_Week15 - Running head: Chapter 15 1 Week 15...

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Running head: Chapter 15 1 Week 15 Written Assignment Jeremy Doncouse Mountain State University
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Running head: Chapter 15 2 Chapter 15: The Peripheral Nervous System and Reflex Activity 1. Describe the structure and function of accessory eye structures, eye layers, the lens, and humors of the eye. Accessory Structures of the Eye: Eyebrows are short, coarse hairs overlying the supraorbital margins of the eye that shade the eyes and keep perspiration out. Eyelids (palpebrae), eyelashes, and their associated glands help to protect the eye from physical danger as well as from drying out. The tarsal glands produce an oily secretion for lubrication and retention of tears. Conjunctiva is a transparent mucous membrane that lines the eyelids and the whites of the eyes. The conjunctiva produces lubricating mucus that prevents the eye from drying out. The lacrimal apparatus consists of the lacrimal gland, which secretes a dilute saline solution that cleanses and protects the eye as it moistens it, and ducts that drain excess fluid into the nasolacrimal duct. Tears contain lysozyme, an enzyme that breaks down bacterial cell walls. The movement of each eyeball is controlled by six extrinsic eye muscles that are innervated by the oculomotor, abducens, and trochlear nerves. Structure of the Eyeball: Three layers form the wall of the eyeball. The fibrous tunic is the outermost coat of the eye and is made of a dense avascular connective tissue with two regions: the sclera and the cornea. The vascular tunic is the middle layer and has three regions: the
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Running head: Chapter 15 3 choroid, the ciliary body, and the iris. The retina is the innermost layer made up of two layers: the outer pigmented layer absorbs light; the inner neural layer contains millions of photoreceptors that transduce light energy. Internal Chambers and Fluids: The posterior segment is filled with a clear gel called vitreous humor that transmits light, supports the posterior surface of the lens, holds the retina firmly against the pigmented layer, and contributes to intraocular pressure. There are tiny collagen fibers in the vitreous humor and they are held apart by their electrical charges. The anterior segment is filled with aqueous humor that supplies nutrients and oxygen to the lens and cornea while carrying away wastes. The lens is an avascular, biconcave, transparent, flexible structure that can change shape to allow precise focusing of light on the retina. The lens contains crystallins, proteins that form the body of the lens. The iris and pupil dilation and constriction: The iris is made up of two layers of smooth muscles: the sphincter pupillae with circular muscles and the dilator pupillae with radial muscles. The neural layer of the retina is composed of several types of neurons:
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This note was uploaded on 03/08/2011 for the course BIO 215 taught by Professor Amirafshar during the Fall '10 term at Mountain State.

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Doncouse_Jeremy_Week15 - Running head: Chapter 15 1 Week 15...

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