Histology Of The Eye Chiaia Anatomy Block Ii Unit Iii

Front 1

4 refractile elements of the eye

Back 1

Cornea, aqueous humor, lens, vitreous humor

Front 2

ora serrata

Back 2

Juncture of neural retina at the ciliary body

Front 3

Zonules of zinn

Back 3

Suspensory ligaments that support the lens and attached to the ciliary body

Front 4

3 chambers of the eye contents and boundaries

Back 4

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

Front 5

Tunica fibrosa

Back 5

Tough fibrous coat of CT

Made up by:
Sclera posteriorly
Cornea anteriorly

Front 6

Sclera

Back 6

White fibrous tissue, covers posterior 5/6 of tunica fibrosa

Front 7

Layers of the sclera

Back 7

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)

Front 8

Lamina cribosa

Back 8

Area where the optic nerve pierces the sclera

Front 9

Limbus

Back 9

Area where the cornea is continuous with the sclera

Front 10

Cornea layers

Back 10

Epithelium
Bowman's Membrane
Lamina Propria
Descemet's Membrane
Corneal endothelium

Front 11

Epithelium of cornea

Back 11

Stratified squamous connected by desmosomes, apical ones have microvilli to maintain fluid
Densly innervated (source of tears and blinking)

Front 12

Tear film layers

Back 12

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

Front 13

Bowman's membrane of cornea

Back 13

Acellular layer composed of collagen fibers, protective barrier against bacterial invasion

Front 14

Lamina propria

Back 14

Thick layer consisting of collagen fibrils, fibrocytes, and amorphous ground substace (keratin and chondroitin sulfates).

Front 15

Descemet's membrane of cornea

Back 15

Thick basement membrane of the final endothelium layer, bound by hemidesmosomes to corneal endothelium

Front 16

Corneal endothelium

Back 16

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

Front 17

Layers of choroid

Back 17

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

Front 18

Iris

Back 18

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)

Front 19

Ciliary body epithelium

Back 19

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

Front 20

Ciliary process

Back 20

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)

Front 21

Functions of ciliary body

Back 21

Source of aqueous humor
Regulates shape of lens

Front 22

Path of Aqueous humor

Back 22

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.

Front 23

Glaucoma

Back 23

Blockage of aqueous drainage an increased intraocular pressure = decreased blood flow and ischemia of retina

Front 24

Ciliary muscle action

Back 24

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)

Front 25

Lens

Back 25

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.

Front 26

Presbyopia

Back 26

Lens fibers harden and lens losses its ability to change shape, necessitates reading glasses.

Front 27

Cataracts

Back 27

Lens becomes semiopaque with age resulting in blured vision

Front 28

Vitreous chamber

Back 28

Contains amorphous ground substance and random collagen fibrils, (soft jello consistency)

Front 29

Cells of the retina

Back 29

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)

Front 30

Layers of the retina

Back 30

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

Front 31

Retinal pigment epithelium

Back 31

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

Front 32

Detached retina

Back 32

Detachment between the retinal pigment epithelium and the underlying photoreceptor layer. This causes loss of nourishment and slow death of the photoreceptors

Front 33

Photoreceptor layer

Back 33

Rods and cones

Front 34

6 parts of photoreceptor cells

Back 34

Outer segment
Cilium
Innersegment
Outer fiber
Cell body
Inner fiber

Front 35

Outer segment part

Back 35

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.

Front 36

Rods and cones

Back 36

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.

Front 37

Cilium part

Back 37

Just below the outer segment, contains a small slender cilium. It is non-motile and connects the outer segment to the inner segment.

Front 38

Inner segment part

Back 38

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.

Front 39

Outer fiber part

Back 39

Inner segment of the photoreceptors connected to the cell body via this.

Surrounded by muller cells which are connected by tight junctions.

Front 40

Cell body part

Back 40

Filled with nucleus

Front 41

Inner fiber part

Back 41

Forms a synaptic contact with underlying bipolar cells

Front 42

Fovea centralis

Back 42

Part where cones are most prevalent of the retina, is near the optic nerve.

Front 43

Retinal transduction

Back 43

Hyperpolarize rods and cone receptors via cGMP and Ca+ dependent modulation of Na+ channels in the photoreceptor membrane

Front 44

External limiting membrane layer

Back 44

Photorecpetors surrounded by muller cells (support glial), not really cells, just zonula adherens junctions between muller cells and photoreceptors.

Front 45

Outer nuclear layer

Back 45

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.

Front 46

Outer plexiform layer

Back 46

Contains synaptic processes of the photoreceptors as they make contact with the dendrites of bipolar and horizontal cells.

Front 47

Inner nuclear layer

Back 47

Cell bodies of bipolar, horizontal, and amacrine cells reside.

Front 48

Inner plexiform layer

Back 48

Clear region where the processes of bipolar, amacrine and ganglion cells interact to process visual information.

Front 49

Ganglion cell layer

Back 49

Contains the cell bodies of the retinal ganglion cells (output neurons that form the optic nerve)

Front 50

Retinal axon layer

Back 50

Region where the unmyelinated ganglion cell axons travel toward the optic disc where they exid the eyeball

Front 51

Internal limiting membrane

Back 51

Basement membrane of the supportive muller cells (not a true membrane)

Front 52

Blood supply of retina

Back 52

Outer 1/3= choroid
Inner 2/3 = retinal arteries and veins in the ganglion layer

Front 53

Cells that sustain nerve impulses

Back 53

Ganglion cells

Front 54

Reactions of photoreceptors to light/dark

Back 54

Increased light causes them to decrease rate of release of neurotransmitters

Decreased light causes an increase in release of photoreceptors

Front 55

Pathway of visual information

Back 55

Photoreceptors to bipolar cells to ganglion cells (horizontal and amacrine mediate lateral interactions across the surface of the retina)

Front 56

Ganglion cells function

Back 56

Encode wheter a contour or edge is present, its color, brightness, and exact position in space.

Front 57

Optic disk

Back 57

A cercular region near the center of the retina where the retinal ganglion cells axons collect and leave the eyeball (blind spot)

Front 58

Fovea

Back 58

A small depression where visual accuity is best, also called the maculae lutea