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58 Cards in this Set

  • Front
  • Back
4 refractile elements of the eye
Cornea, aqueous humor, lens, vitreous humor
ora serrata
Juncture of neural retina at the ciliary body
Zonules of zinn
Suspensory ligaments that support the lens and attached to the ciliary body
3 chambers of the eye contents and boundaries
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
Tunica fibrosa
Tough fibrous coat of CT

Made up by:
Sclera posteriorly
Cornea anteriorly
White fibrous tissue, covers posterior 5/6 of tunica fibrosa
Layers of the sclera
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)
Lamina cribosa
Area where the optic nerve pierces the sclera
Area where the cornea is continuous with the sclera
Cornea layers
Bowman's Membrane
Lamina Propria
Descemet's Membrane
Corneal endothelium
Epithelium of cornea
Stratified squamous connected by desmosomes, apical ones have microvilli to maintain fluid
Densly innervated (source of tears and blinking)
Tear film layers
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
Bowman's membrane of cornea
Acellular layer composed of collagen fibers, protective barrier against bacterial invasion
Lamina propria
Thick layer consisting of collagen fibrils, fibrocytes, and amorphous ground substace (keratin and chondroitin sulfates).
Descemet's membrane of cornea
Thick basement membrane of the final endothelium layer, bound by hemidesmosomes to corneal endothelium
Corneal endothelium
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
Layers of choroid
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

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
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)
Ciliary body epithelium
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
Ciliary process
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)
Functions of ciliary body
Source of aqueous humor
Regulates shape of lens
Path of Aqueous humor
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.
Blockage of aqueous drainage an increased intraocular pressure = decreased blood flow and ischemia of retina
Ciliary muscle action
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)
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.
Lens fibers harden and lens losses its ability to change shape, necessitates reading glasses.
Lens becomes semiopaque with age resulting in blured vision
Vitreous chamber
Contains amorphous ground substance and random collagen fibrils, (soft jello consistency)
Cells of the retina
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)
Layers of the retina
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
Retinal pigment epithelium
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
Detached retina
Detachment between the retinal pigment epithelium and the underlying photoreceptor layer. This causes loss of nourishment and slow death of the photoreceptors
Photoreceptor layer
Rods and cones
6 parts of photoreceptor cells
Outer segment
Outer fiber
Cell body
Inner fiber
Outer segment part
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.
Rods and cones
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.
Cilium part
Just below the outer segment, contains a small slender cilium. It is non-motile and connects the outer segment to the inner segment.
Inner segment part
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.
Outer fiber part
Inner segment of the photoreceptors connected to the cell body via this.

Surrounded by muller cells which are connected by tight junctions.
Cell body part
Filled with nucleus
Inner fiber part
Forms a synaptic contact with underlying bipolar cells
Fovea centralis
Part where cones are most prevalent of the retina, is near the optic nerve.
Retinal transduction
Hyperpolarize rods and cone receptors via cGMP and Ca+ dependent modulation of Na+ channels in the photoreceptor membrane
External limiting membrane layer
Photorecpetors surrounded by muller cells (support glial), not really cells, just zonula adherens junctions between muller cells and photoreceptors.
Outer nuclear layer
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.
Outer plexiform layer
Contains synaptic processes of the photoreceptors as they make contact with the dendrites of bipolar and horizontal cells.
Inner nuclear layer
Cell bodies of bipolar, horizontal, and amacrine cells reside.
Inner plexiform layer
Clear region where the processes of bipolar, amacrine and ganglion cells interact to process visual information.
Ganglion cell layer
Contains the cell bodies of the retinal ganglion cells (output neurons that form the optic nerve)
Retinal axon layer
Region where the unmyelinated ganglion cell axons travel toward the optic disc where they exid the eyeball
Internal limiting membrane
Basement membrane of the supportive muller cells (not a true membrane)
Blood supply of retina
Outer 1/3= choroid
Inner 2/3 = retinal arteries and veins in the ganglion layer
Cells that sustain nerve impulses
Ganglion cells
Reactions of photoreceptors to light/dark
Increased light causes them to decrease rate of release of neurotransmitters

Decreased light causes an increase in release of photoreceptors
Pathway of visual information
Photoreceptors to bipolar cells to ganglion cells (horizontal and amacrine mediate lateral interactions across the surface of the retina)
Ganglion cells function
Encode wheter a contour or edge is present, its color, brightness, and exact position in space.
Optic disk
A cercular region near the center of the retina where the retinal ganglion cells axons collect and leave the eyeball (blind spot)
A small depression where visual accuity is best, also called the maculae lutea