Mkgrady8 Neuro 2 Histo Of The Eye

Front 1

the 3 layers of the eye

Back 1

from innermost to outermost= retina (neural retina plus pigmented epi, non neural retina of epi of ciliary body and iris), uvea (choroid, ciliary body, body of iris), sclera (sclera plus cornea0

Front 2

the 3 chambers of the eye

Back 2

anterior, posterior, and vitreous

Front 3

the 3 functional groups of structures in the eye

Back 3

light focusing structures including the cornea and the lens (plus associated structures); light detecting structures including photoreceptor layer of the retina; signal modifying and transmitting structures including the rest of the retina and the optic nerve

Front 4

the cornea: blood supply, nerve supply, what does it do

Back 4

translucent and avascular but does contain free nerve endings; most refraction accomplished here; can be transplanted easily

Front 5

cornea: 5 histological layers (in order of outer to inner layers PLEASE REMEMBER)

Back 5

EPITHELIUM= stratified, non keratinized squamous; BOWMAN'S MEMBRANE= thick, acellular layer underneath the epi basement membrane; STROMA= connective tissue, regular arrays of collagen fibers; DESCEMET'S MEMBRANE= basement membrane of endothelium; ENDOTHELIUM= simple, tall squamous to low cuboidal

Front 6

for optimal translucency what layer must be kept relatively dehydrated and how is this accomplished and what results if it isn't

Back 6

stromal layer; Na pumps in the endothelial cells; malfunction results in stromal edema

Front 7

CORNEAL DYSTROPHIES: what is it, onset

Back 7

a dystrophy of the cornea is defined as a bilateral noninflammatory clouding of the cornea; most show onset before 20 yrs and may be genetically dominant or recessive (depending on type); the defect appears to correlate with AN ERROR IN THE SYNTHESIS OF KERATAN SULFATE OR DECORIN, COMMON GLYCOSAMINOGLYCANS/PROTEOGLYCANS therefore symptoms are not restricted to the eye

Front 8

CORNEAL DEGENERATIONS: what is it

Back 8

keratopathies; may be caused by abnormal calcium deposition in Bowman's layer or DEGENERATION OF COLLAGEN in the stroma due to excessive UV exposure

Front 9

LASIK TREATMENT: what is it

Back 9

resculpting the cornea with lasers in order to restore normal refractive properties; HE SKIPPED THIS

Front 10

CORNEAL TRANSPLANTS: how effective and why

Back 10

very effective due in part to the avascular nature of the stroma and also because often the endothelial layer is retained; HE SKIPPED THIS

Front 11

SCLERA: what is it made of/look like, where is it, what is its main function

Back 11

dense irregular connective tissue; covers the entire surface of the eye except for the cornea; openings in the sclera called the LAMINA CRIBROSA mark the site of exit of the retinal axons leaving the eye to form the optic nerve, these openings in the sclera allow passage of the axons through them; the sclera is opaque and is the site of insertion of eye muscles; the cornea-sclera junction is called the LIMBUS and is the site of corneal 'stem cells'; one main function of the sclera is to guard against physical damage to the eye

Front 12

ANTERIOR CHAMBER: where is it, what does it contain

Back 12

the area bounded by the cornea, iris, and lens; contains aqueous humor similar in composition to plasma (although much lower in protein) and supplies nutrients to the cornea and lens; trabecular meshwork= a loose meshwork of connective tissue fibers located in the angle of the iris, leads to the canal of schlemm, is the initial site of drainage of aqueous humor; canal of schlemm (scleral venous sinus)= located anteriorly to the iris, drains the aqueous humor and delivers it back to the bloodstream

Front 13

POSTERIOR CHAMBER: where is it, what does it contain

Back 13

the area bounded by the IRIS, CILIARY BODY, SUSPENSORY LIGAMENT, and the LENS; also contains aqueous humor

Front 14

the aqueous humor: what makes it, how much is produced, how is it drained, what can go wrong

Back 14

secreted by the CILIARY body; enough is produced to turn over its entire volume 12 times/day; because it is constantly being made aqueous humor must also be drained in order to maintain proper intraocular pressure; drainage pattern is posterior chamber to anterior chamber (through the pupil), anterior chamber to the trabecular meshwork, located in the limbus, trabecular meshwork to the Canal of Schlemm; from the canal of schlemm, the aqueous humor drains into a plexus of episcleral veins that delivers it back into the bloodstream; faulty drainage (blockage of meshwork of canal) leads to GLAUCOMA; KNOW WHAT THE CANAL OF SCHLEMM DOES, WHERE IT IS, WHAT IS LOOKS LIKE

Front 15

VITREOUS BODY: where is it, what does it contain

Back 15

located between the lens and the retina; contains a semi solid VITREOUS HUMOR containing hyaluronic acid and other glycoproteins, macrophages are also present to clean up any debris that might form

Front 16

IRIS: what is it, what does it contain, where it is (what layer is it a part of), 2 functions, what does it separate

Back 16

a pigmented diaphragm that contains smooth muscle; contains loose connective tissue, blood vessels, pigmented cells, etc; possesses a layer of pigmented, cuboidal epi on its posterior surface, no epi on its anterior surface but instead exhibits a discontinuous layer of fibroblasts and melanocytes and both the number of melanocytes and their relative content of melanin determine eye color; the iris represents the most anterior portion of the uveal layer; function is to control the amount of light that reaches the lend, via the pupil; function in adjusting the depth of field of vision; separates the anterior from the posterior chamber

Front 17

smooth muscle control of pupillary diameter: which muscles, where are they, what do they each do, what controls them

Back 17

constrictor pupillae= narrows the diameter of the pupil, is a circular smooth muscle near the free margin, under PARASYMPATHETIC CONTROL (CN III); dilator pupillae= radially arranged 'muscle', composed of myoepithelial cells that comprise the inner layer of cells of the posterior side of the iris, enlarges pupillary diameter, under SYMPATHETIC CONTROL via the superior cervical ganglion

Front 18

LENS: what is it, what is it surrounded by,

Back 18

a biconcave structure composed of transparent specialized epi cells that are very long and their length is oriented anteroposteriorly; surrounded by a 'capsule' that allows the lens to change shape for more precise focusing (accommodation); the lens lasts (hopefully) a lifetime and although there is no real turnover cells may proliferate (slowly) and add 'lens fibers' to the periphery

Front 19

LENS: components and what can go wrong in old age

Back 19

acellular capsule= really the basement membrane of the lens epi cells (type 4 collagen) and loss of elasticity with age results in presbyopia (diminished capacity to round up for precise near vision focusing); anterior epi= single layer of cuboidal cells; mature lens fibers= greatly elongated epi cells, prism shaped and without nuclei; new lens fibers form at the equator of the lens and compress the more centrally located cells as they are added to the body of the lens; SUSPENSORY LIGAMENT (ZONULE FIBERS)= accessory structures that attach the lens to the periphery of the eye at the ciliary processes, are composed of microfibrils (one component of elastic fibers) and are called OXYTALIN FIBERS (general term and here they are called zonule fibers)

Front 20

LENS: clinical significance CATARACTS: what are they, causes, treatment

Back 20

loss of transparency of the lens; most people will eventually experience some cloudiness of the lens; transparency loss is due to conformational changes in the prominent proteins in the lens fibers leading to their aggregation and/or cross linking; may have any of several causes= disease processes, genetics, trauma, excessive exposure to UV irradiation; when it impedes sight significantly the lens is removed surgically and a synthetic lens is dropped inside the capsule

Front 21

CILIARY BODY: what and where, what does it do, what controls it

Back 21

an extension of the uveal tract containing smooth muscle arranged in several planes; contraction of these fibers results in decreased tension on the zonule fibers of the lens allowing the lens to round up (its relaxed state) this shortens focal length and accomodates for near vision; under parasympathetic control (CN3)

Front 22

CILIARY PROCESSES: what and where, function

Back 22

processes that extend inward from the ciliary body to the posterior chamber; possess a vascular core that is surrounded by a double layer of epi with the inner layer being unpigmented and the outer layer being pigmented; main function is to secrete aqueous humor

Front 23

ORA SERRATA: what and where

Back 23

the junction between the neural and non neural parts of the retina and at this point the 10 layers of the neural retina are reduced to 2; has a wavy or scalloped appearance; also demarcates the posterior edge of the ciliary body

Front 24

CHOROID: what and where, function

Back 24

is a well vascularized layer lying just outward of the retina; also possesses pigmented cells; function= to provide nutrition for the retina and to absorb scattered light

Front 25

RETINA: what and where

Back 25

a very complex structure the neural part of which possesses 10 very well organized layers; this is where the rods and cones are located and where photoreception occurs

Front 26

name the layers of the retina (10 of them) from outer to inner PLEASE REMEMBER THEM

Back 26

pigmented epi, photoreceptor layer (layer of rods and cones), external limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, nerve fiber layer, internal limiting membrane

Front 27

pigmented epithelium (P.E.): what is it, what can go wrong, function

Back 27

a single layer of melanin rich cuboidal/low columnar epi cells; they are attached more firmly to the choroid than to the rest of the retina and as a result the potential space between the P.E. and the photoreceptor layer allows RETINAL DETACHMENT to occur; the melanin absorbs light that would otherwise reflect back to the photoreceptors; P.E. cells have microvilli that engulf the outer segments of the photoreceptors; phagocytoses spent photoreceptor discs that are shed from the rods and cones; it also stores and releases vit A to the photoreceptors; CLINICAL SIGNIFICANCE= hereditary retinal dystrophy results from the P.E.'s inability to phagocytose worn out discs

Front 28

photoreceptor layer (layer of rods and cones): what are rods and cones

Back 28

rods and cones are highly specialized neurons that detect, transduce, and transmit light energy as neural signals; more specificially this layer contains the outer segments of the rods and cones

Front 29

rods: what are they, function

Back 29

tall cylindrical cells; sensitive to low light levels; function in peripheral and nocturnal (scotopic) vision; the outer segments are actually modified cilia that contain membranous 'discs' derived from the plasma membrane; these membranes contain the visual pigment rhodopsin (a derivative of vit A) which transduces light energy into a neural signal that is processed and passed on to the brain by succeeding layers of neurons; rods are more numerous than cones except for the area called the FOVEA; comprise a large proportion of photoreceptor cells at the retinal periphery

Front 30

cones: what are they, function

Back 30

cone shaped cells; these cells mediate color vision, pattern detection, and fine detail; are sensitive to light at higher amplitudes (photopic vision); possess discs similar to those observed in rods; visual pigments are sensitive to light in either the blue, green, or red parts of the visual spectrum of light; the cones tend to predominante in the more ventral part of retina; in the FOVEOLA (VERY CENTRAL PART OF THE FOVEA) there are only cones

Front 31

external limiting membrane: what is it

Back 31

observable as a line by light microscopy it represents the desmosome like functions between the photoreceptor cells and the surrounding supporting cells called MULLER CELLS

Front 32

outer nuclear layer: what is it

Back 32

the somas and nuclei of the PHOTORECEPTOR CELLS

Front 33

outer plexiform layer: what happens where

Back 33

this area is where synapses among the axons of photoreceptor cells, BIPOLAR NEURONS AND HORIZONTAL CELLS occur; horizontal cells are association neurons involved in the local processing of visual info

Front 34

inner nuclear layer: what is here

Back 34

somas and nuclei of (mostly) bipolar cells plus the nuclei of Muller cells and other associational calls; bipolar cells are the main link between the photoreceptor cells and the ganglion cells and are the main link in transmission of visual info

Front 35

inner plexiform layer: what is here

Back 35

area of synapses among bipolar cells, ganglion cells, and AMACRINE CELLS; amacrine cells are also associational neurons involved in the local integration and processing of visual info

Front 36

ganglion cell layer: what is here

Back 36

occupied by the somas and nuclei of the GANGLION CELL NEURONS= the only output cells of the retina; they receive input from the bipolar cells

Front 37

nerve fiber layer: what is here

Back 37

the unmyelinated axons of the ganglion cells; they follow the curvature of the eye and exit at the optic disc; they become myelinated as the optic nerve once they've exited the eye via the lamina cribrosa

Front 38

internal limiting membrane: what is here

Back 38

the thin basal lamina generated by the Muller cells; it is in direct contact with the vitreous body and appears as a line by light microscopy

Front 39

how image transmission works: a brief summary

Back 39

light must pass through several translucent structures (cornea, lens, aqueous and vitreous humors, most of the retina) in order to excite the pigments of the rods and cones (the latter are the only light sensitive components of the retina); the result of activation of photoreceptors is hyperpolarization to generate a receptor potential; the signal is then propagated to the bipolar cells where the associational neurons modify the signal before its output from the ganglion cell axons; from the bipolar cells the signal is transmitted to the ganglion cells (where more associational interactions with amacrine cells occurs); the ganglion cells transmit the info to the brain via CN2 (the optic nerve)

Front 40

the MACULE (macula lutea or yellow spot): what does it contain, function, location, what can go wrong

Back 40

contains much xanthophyll pigment which absorbs much UV light and protects the photoreceptors in this area; contains the FOVEA (a depression in the retina that is enriched in cones and the foveola which contains only cones); located laterally (temporally) to the optic disc; it is the area of most acute vision; MACULAR DEGENERATION is a common cause of blindness in older adults

Front 41

the OPTIC DISC (optic papilla or blind spot): what is it, what is here, location

Back 41

it is the site of emergence of the accumulated, unmyelinated axons of the ganglion cells to become myelinated as the optic nerve; there are no rods or cones here therefore it truly is a blind spot; this is also the site of entry and exit of the vasculature of the eye; it is located nasally to the macula

Front 42

causes of vision impairment and loss: refractive error: correctable with

Back 42

glasses or contacts

Front 43

causes of vision impairment and loss: macular degeneration: what is involved

Back 43

age related, called ARMD, may or may not involve neovascularization (wet or dry ARMD)

Front 44

causes of vision impairment and loss: cataracts

Back 44

discussed above

Front 45

causes of vision impairment and loss: glaucoma: what is involved

Back 45

a number of different types; involves blockage of drainage of the aqueous humor

Front 46

causes of vision impairment and loss: diabetic retinopathy: what is involved

Back 46

diabetes may affect multiple ocular structures, including the lens and the retina

Front 47

causes of vision impairment and loss: retinoblastoma: what is involved

Back 47

the most common primary intraocular tumor of children

Front 48

causes of vision impairment and loss: retinitis pigmentosa: what is involved

Back 48

misnomer; not an inflammatory disease; involves progressive loss of both rods and cones via apoptosis