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| 1. Know the 4 groups of accessory structures of the eyes. |
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Definition
•Eyelids and associated exocrine glands
•The superficial epithelium of the eye
Structures associated with the production, secretion, and removal of tears
•The extrinsic eye muscles |
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| eyelids- a continuation of the skin |
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| (lateral and medial)connect the upper and lower eyelids |
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| (lacrimal) a soft mass of tissue, contains glands that produce thick secretions that contribute to the gritty deposits occasionally found after a night’s sleep |
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| - modified sebaceous glands that secrete a lipid-rich product that keeps the eyelids from sticking together |
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| an infection in a sebaceous gland of one of the eyelashes, in a tarsal gland, or in one of the sweat glands between the eyelash follicles produces a painful localized swelling |
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| - thin, transparent mucous membrane that covers the inner surfaces of the eyelids and the outer, white surface of the eye (sclera) |
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| delicate, continuous with the conjunctiva, covers the cornea |
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| tear gland, superior and lateral to the eyeball; which has a dozen or more ducts that empty into the pocket between the eyelid and the eye |
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Definition
| passageways that end at the lacrimal sac |
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Definition
| from the lacrimal sac, it carries the tears to the nasal cavity |
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| 3. Know the six extrinsic eye muscles and cranial nerve that serves each one. |
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Definition
• Inferior rectus- Oculomotor nerve (N III)
• Medial rectus- “ “
• Superior rectus- “ “
• Lateral rectus- Abducens (N VI)
• Inferior oblique- Oculomotor
• Superior oblique- Trochlear nerve (N IV) |
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Term
| 4. Know the Cavities and chambers of the eye. |
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Definition
• Posterior cavity- (vitreous chamber) large, contains the gelatinous vitreous body
• Anterior cavity- smaller, is subdivided into the anterior chamber and the posterior chamber
o Anterior chamber
o Posterior chamber |
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Term
| Describe the fibrous layer of the eye |
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Definition
| outermost, consists of the sclera and the cornea; provides mechanical support and some degree of physical protection, serves as an attachment site for the extrinsic eye muscles, and assists in the focusing process |
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Term
| Describe the vascular layer of the eye |
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Definition
| intermediate, contains numerous blood vessels, lymphatic vessels, and the intrinsic blood vessels, it also includes the iris, the ciliary body, and the choroid; providing a route for blood vessels and lymphatic vessels that supply tissues of the eye, regulating the amount of light entering the eye, secreting and reabsorbing the aqueous humor that circulates within the chambers of the eye, and controlling the shape of the lens, an essential part of the focusing process |
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| Describe the inner layer of the eye |
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Definition
| (retina) deep, consists of a thin, outer pigment layer called the pigmented part and a thick, inner layer called the neural part |
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Term
| 6. Describe the organization of the retina. |
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Definition
| The neural part of the retina contains several layers of cells. The outermost layer, closest to the wall of the pigmented part of the retina, contains the photoreceptors: rods and cones |
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Definition
| do not discriminate among colors of light, enable us to see in dimly lit rooms |
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| provide us with color vision, three types which provide the perception of different colors, give us sharper, clearer images, but require brighter light |
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| where most cones are concentrated and where the visual image arrives after passing through the cornea and lens |
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| the center of the macula where most of the cones are concentrated; center of color vision and the site of sharpest vision |
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Definition
| a circular region just medial to the fovea; the origin of the optic nerve |
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Definition
| light striking this area goes unnoticed |
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| circulates within the chamber of the eye |
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Definition
| a clear gelatinous substance that fills the anterior cavity |
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Term
| Sclera venous sinus (canal of Schlemm) |
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Definition
| this passageway empties into veins in the sclera and returns the aqueous humor to the venous system |
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Term
| 8. Explain accommodation, image formation |
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Definition
| The process of focusing an image on the retina by changing the shape of the lens, the lens either becomes rounder (nearby) or flattens (distance) |
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| seeing close up objects becomes more difficult, and older individuals become fatsighted |
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| this condition is typically associated with the growth and proliferation of blood vessels in the retina |
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| eye disorder characterized by rising intraocular pressures due to inadequate drainage of aqueous humor at the canal of Schlemm |
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Definition
| when the balance of precise combination of structural and biochemical characteristics is disturbed, the lens loses it transparency |
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| a person with this vision can see details at a distance of 20 ft. as clearly as a "normal" individual would |
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| when Vitamin A reserves are depleted and the amount of visual pigment in the photoreceptors begins to decline, and the dim light proves insufficient to activate the rods |
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| persons unable to distinguish certain colors |
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| 11. Describe photoreceptor structure |
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Definition
| The outer segment contains hundreds to thousands of flattened membranous discs; the inner segment contains typical cellular organelles and forms synapses with other cells |
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Definition
| The residual electric current flowing in a photoelectric device when there is no incident illumination |
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| the reverse of light adaptation. It occurs when going from a well light area to a dark area. Initially blackness is seen because our cones cease functioning in low intensity light. Also, all the rod pigments have been bleached out due to the bright light and the rods are initially nonfunctional. Once in the dark, rhodopsin regenerates and the sensitivity of the retina increases over time (this can take approximately one hour). During these adaptation process reflexive changes occur in the pupil size. |
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Definition
| occurs when we move from the dark into bright light. The bright light momentarily dazzles us and all we see is white light because the sensitivity of the receptors is set to dim light. Rods and cones are both stimulated and large amounts of the photopigment are broken down instantaneously, producing a flood of signals resulting in the glare. |
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Definition
| shortly after the retinal changes shape, the rhodopsin molecule begins to break down into retinal and opsin |
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| visual pigment that "senses" light in the rod cells of the retina |
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| 14. Describe the visual pathway and where optic information travels in the brain (for sight, for circadian rhythms and for reflexes). |
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Definition
| it begins at the photoreceptors and end at the visual cortex of the cerebral hemispheres; the message must cross two synapses (photoreceptor to bipolar cell and bipolar cell to ganglion cell) before it moves into the brain. |
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