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58 Cards in this Set
- Front
- Back
4 refractile elements of the eye
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Cornea, aqueous humor, lens, vitreous humor
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ora serrata
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Juncture of neural retina at the ciliary body
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Zonules of zinn
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Suspensory ligaments that support the lens and attached to the ciliary body
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3 chambers of the eye contents and boundaries
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Anterior chamber- bound by iris and cornea
Posterior chamber- bound by the lens, iris, and ciliary body Both of these are filled with nutritive ultrafiltrate of plama called aqueous humor, which is produced by the epithelium of the ciliary body Vitreous chamber- bounded by the lens and the posterior wall of the eyeball, filled with vitreous body and helps to shape the eye and hold the lens and retinal layers in place |
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Tunica fibrosa
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Tough fibrous coat of CT
Made up by: Sclera posteriorly Cornea anteriorly |
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Sclera
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White fibrous tissue, covers posterior 5/6 of tunica fibrosa
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Layers of the sclera
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1) episclera, vascularized CT, attached to Tennon's capsule
2) Scleral stroma- sheets of collagen fibers in different orientations parallel to the surfce contain melanocytes, fibrocytes, amorphous ground substance, and elastic fibers, high water content, avascular 3)Lamina fusca- Innermost layer, fine collagen fibers that blend with the choroid layer of the eye, contains collagen fibers (like a basement membrane) |
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Lamina cribosa
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Area where the optic nerve pierces the sclera
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Limbus
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Area where the cornea is continuous with the sclera
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Cornea layers
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Epithelium
Bowman's Membrane Lamina Propria Descemet's Membrane Corneal endothelium |
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Epithelium of cornea
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Stratified squamous connected by desmosomes, apical ones have microvilli to maintain fluid
Densly innervated (source of tears and blinking) |
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Tear film layers
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Superficial layer- oily secretion derived from sebaceous glands of inner eyelid
Middle layer- watery fluid derived from the lacrimal glands, contains lysozymes and immonoglobulins Inner layer- consists of mucopolysacharides secreted by goblet cells of the conjuctiva |
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Bowman's membrane of cornea
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Acellular layer composed of collagen fibers, protective barrier against bacterial invasion
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Lamina propria
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Thick layer consisting of collagen fibrils, fibrocytes, and amorphous ground substace (keratin and chondroitin sulfates).
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Descemet's membrane of cornea
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Thick basement membrane of the final endothelium layer, bound by hemidesmosomes to corneal endothelium
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Corneal endothelium
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Simple squmous
Inner lining of cornea Actively transports water out of lamina propra to maintain corneal clarity Liked by desmosomes and occulding junctions Endothelial cells are responsible for secreting descement's membrane |
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Layers of choroid
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1)Suprachoriod
immediately adjacent to inner sclera, loose CT with elastic fibers that anchor it to underlying sclera 2) Vessel layer High collagen content Numerous choriodal arteries and veins Numerous melanocytes which serve to absorb scattered light 3)Choriocapillaris Single layer of wide fenestrated capillaries that nourish surrounding tissues and outer 1/3 of retinal coat 4)Bruch's Glassy membrane formed by network of collagen and elastic fibers sandwiched in between the baasement mebranes of the choriocapillaris on one side and the retinal pigment epithelium on the other |
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Iris
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1) Anterior limiting layer
Discontinous layer of stromal cells with stellate fibroblasts and melanocytes 2) Stroma Vascularized loose CT containing melanocytes and fibroblasts 3)Muscular layer Two bands of smooth muscle embedded in stroma of the iris Sphincter pupillae and dilator papillae 4) Posterior epithelium Simple cuboidal pigment epithelium (continous with retinal epithelium) |
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Ciliary body epithelium
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Continuation of choroid
Covered by a double cuboidal epithleium consisting of a superficial non-pigmented layer and a deep pigmented layer The apical surfaces of the two layers face one another and are connected by desmosomes Numerous fenestrated capillaries are present within the underlying CT |
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Ciliary process
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Ridges on inner edge of the ciliary body that are attached to the zonules of Zinn (baement membrane of superficial layer of non-pigmented epithelial cells)
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Functions of ciliary body
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Source of aqueous humor
Regulates shape of lens |
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Path of Aqueous humor
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From blood vessels into posterior chamber by capillaries of the ciliary processes
It is transported out of the interior of the cilary body by pigment epithelial cells that provide a blood-aqueous barrier Flows into anterior chamber and is drained by microtrebecular meshwork (fibrous channels that filter out pathogens and particulate matter), Enter into Canal of Schlemm (simple squamous epithelium), then into aqueous veins to the conjuctiva to be released into venous blood. |
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Glaucoma
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Blockage of aqueous drainage an increased intraocular pressure = decreased blood flow and ischemia of retina
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Ciliary muscle action
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Parasympathetic
Contraction of cilary muscles results in release of tension on the zonules of zinn and a rounding of the lens for close vision At rest the elastic chord pulls the ciliary body back ward and pulls out ward and backward on the zonules of zinn (Eyeball has a larger diameter) |
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Lens
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Anterior surface, acellular elastic capsule rich in type IV collagen and proteoglycans associated with basement membrane of simple cuboidal epithelium
Lens Is avascular and contains no CT, only modified epithelial cells with a germinal zone on the equatorial rim of the lens Inside epithelium elongates to form lens fibers (transparent proteins called crystallins) These fibers are connected by Knob and socket-like depressions containing tight and gap junctions. |
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Presbyopia
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Lens fibers harden and lens losses its ability to change shape, necessitates reading glasses.
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Cataracts
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Lens becomes semiopaque with age resulting in blured vision
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Vitreous chamber
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Contains amorphous ground substance and random collagen fibrils, (soft jello consistency)
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Cells of the retina
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Photoreceptors (rods and cones)
Bipolar cells (2nd order neurons that recieve neural impulse from photoreceptors and transmit them to 3rd order ganglion cells Horizontal cells (2nd order neurons that interconnect photoreceptors laterally) Amacrine cells (distribute impulses from bipolar cells laterally to retinal ganglion cells Ganglion cells (3rd order cells whose axons exit the retina at the optic disk to form the optic nerve) Muller cells (large glia cells that extend through all 10 layers of the retina. They wrap around the photoreceptor serving to insulate them from one another. Their nuclear are found in the inner nuclear layer) |
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Layers of the retina
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Retinal pigment epithelium
Photoreceptor layer External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Retinal axon layer Internal limiting membrane |
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Retinal pigment epithelium
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Single layer of cuboidal-columnar epithelium that lies between the retina and th choriod in the posterior poriton of the eye and extends over the ciliary body and the posterior iris.
Base is attached to Bruch's membrane of the choriod. Apical surface have microvilli and cytoplasmic sheaths that nourish retinal photoreceptors and phagocytose their waste. Form the blood retina barrier Contain melanin that prevents light from being scattered in the back part of the eyeball |
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Detached retina
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Detachment between the retinal pigment epithelium and the underlying photoreceptor layer. This causes loss of nourishment and slow death of the photoreceptors
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Photoreceptor layer
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Rods and cones
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6 parts of photoreceptor cells
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Outer segment
Cilium Innersegment Outer fiber Cell body Inner fiber |
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Outer segment part
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Composed of dense vertical stacks of membrane bound disks that arise from the apical surface of the membrane
light sensitive portion of receptors. Disks of the phoreceptors contain reninene and opsine (vitamin A derivatives) The rod photopigment is called rhodopsin and the cones contain photopsin. |
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Rods and cones
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Rods support scoptic vision (dim light) and contain rhodopsin and their inner fiber is called spherule.
Cones support daylight color vision and contain photopsin and their inner fiber is called the pedicle. |
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Cilium part
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Just below the outer segment, contains a small slender cilium. It is non-motile and connects the outer segment to the inner segment.
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Inner segment part
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Thicker ellipsoid shaped region of the cell which contains most of the organelles (NOT THE NUCLEUS). Contains numerous K+ channels which are active in the phototransduction process.
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Outer fiber part
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Inner segment of the photoreceptors connected to the cell body via this.
Surrounded by muller cells which are connected by tight junctions. |
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Cell body part
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Filled with nucleus
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Inner fiber part
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Forms a synaptic contact with underlying bipolar cells
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Fovea centralis
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Part where cones are most prevalent of the retina, is near the optic nerve.
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Retinal transduction
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Hyperpolarize rods and cone receptors via cGMP and Ca+ dependent modulation of Na+ channels in the photoreceptor membrane
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External limiting membrane layer
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Photorecpetors surrounded by muller cells (support glial), not really cells, just zonula adherens junctions between muller cells and photoreceptors.
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Outer nuclear layer
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Region where the nuclei of the photoreceptor cells (rods and cones) reside. The nuclei are at different distances from the external limiting membrane giveing the layer the appearance of stratified epithelium.
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Outer plexiform layer
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Contains synaptic processes of the photoreceptors as they make contact with the dendrites of bipolar and horizontal cells.
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Inner nuclear layer
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Cell bodies of bipolar, horizontal, and amacrine cells reside.
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Inner plexiform layer
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Clear region where the processes of bipolar, amacrine and ganglion cells interact to process visual information.
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Ganglion cell layer
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Contains the cell bodies of the retinal ganglion cells (output neurons that form the optic nerve)
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Retinal axon layer
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Region where the unmyelinated ganglion cell axons travel toward the optic disc where they exid the eyeball
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Internal limiting membrane
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Basement membrane of the supportive muller cells (not a true membrane)
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Blood supply of retina
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Outer 1/3= choroid
Inner 2/3 = retinal arteries and veins in the ganglion layer |
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Cells that sustain nerve impulses
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Ganglion cells
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Reactions of photoreceptors to light/dark
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Increased light causes them to decrease rate of release of neurotransmitters
Decreased light causes an increase in release of photoreceptors |
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Pathway of visual information
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Photoreceptors to bipolar cells to ganglion cells (horizontal and amacrine mediate lateral interactions across the surface of the retina)
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Ganglion cells function
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Encode wheter a contour or edge is present, its color, brightness, and exact position in space.
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Optic disk
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A cercular region near the center of the retina where the retinal ganglion cells axons collect and leave the eyeball (blind spot)
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Fovea
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A small depression where visual accuity is best, also called the maculae lutea
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