Eye Flashcards
eyelid
function
protect eyeball, maintain moisture
eyelid structure
thin skine externally
+ palpebral conjunctiva internal
+ tarsal plates “skeleton”
eyelid glands
- sebaceous of eyelashes (Zeis), bacterial infections = styes
- apocrine of eyelashes (Moll), modified sweat glands
- tarsal (Meibomian), sebaceous glands w/i tarsal plates>secretions slow evap of tears> open onto edge of eyelid
-Chalazion = inflammation of tarsal glands
conjunctiva
function
maintain moisture, lubricate outside of eye so no pain when blinking
conjunctiva structure
two parts:
1. bulbar (cover sclera)
2. palpebral (cover inside eyelid)
stratified columnar w/ goblet cells to lubricate/protect anterior eye»_space; stratified squamous @corneoscleral limbus
lacrimal apparatus function
maintain moisture, remove foreign materials via tears
lacrimal gland
compound tubuloacinar shape
secretes lacrimal fluid aka tears
-sterile (mostly water) + lysozyme
lacrimal fluid flow
lateral > medial
1. lacrimal gland
2. lacrimal duct
3. lacrimal canaliculi (strat squamous)
4. lacrimal sac (pseudostrat ciliated)
5. nasal cavity (pseudostrat ciliated)
pseduostratified ciliated columnar = respiratory epithelium
chambers/segments of eye
- anterior segment @ant to lens w/ aqueous humor
- anterior chamber (cornea>iris)
- posterior chamber (iris>lens) - posterior segment @post to lens w/ vitreous humor
parts of anterior segment
- ciliary body
- iris
- pupil
- cornea
- sclera
parts of posterior segment
- choroid
- retina
- vitreous body (transparent gel 99% water)
- sclera
other 1% = collagen, hyaluronic acid, hyaloctyes, macrophages
eye development
neuroectoderm
- optic vesicle
- optic cup
- inner and outer layer
-inner = neural retina
-outer = retinal pigment epithelium (RPE)
eye development
surface ectoderm
- surface ectoderm
- lens placode and corneal epithelium
-lens placode >lens vesicle> lens
lens structure
- lens capsule- basal lamina of subcap
- subcapsular epithelium- simple cuboidal, only on anterior lens
- lens fibers- mature fibers w/o nuclei + acquire crystallins to inc refractory index
layers of eye
general - 3
- fibrous (sclera + cornea)
- vascular (iris + ciliary body + choroid)
- retina (RPE + neural retina)
sclera
@fibrous layer, posterior 5/6 eye
mostly collagen + elastic fibers
all extraocular muscles insert
will continue to cornea @corneoscleral limbus
cornea
anterior 1/6th eyeball
transparent and avascular
highly innervated
provides most refraction of light
corneoscleral limbus structure
trabecular meshwork (drain aq humor from ant chamber) aka spaces of fontana >combine to form scleral venous sinus aka canal of schlemm
flow of aqueous humor
- produced by ciliary epithelium
- secreted to post chamber
- flow into ant chamber thru pupil
- drain thru trabecular meshwork
- drain in scleral venous sinus
- drain to scleral veins
cornea layers
- epithelium
- bowman’s membrane
- stroma
- pre-descemet
- descemet membrane
- endothelium
epithelium of cornea
strat squamous non keratin, has surface cells w/ microvilli, richly inn, replaced every 7 days
layer 1/6
bowman’s membrane
cornea
acellular/no regen, ends @ corneoscleral limbus, strengthens cornea + barrier to infectin
layer 2/6
stroma
cornea
aka substantia propria, 90% of corneal thickness, orthogonal lamellae of collagen fibrils = transparency maintain
layer 3/6
pre-descemet layer
cornea
protect cornea from damage, rupture = aq fluid leaking into cornea
layer 4/6
descemet membrane
basal lamina of corneal endothelium, helps maintain curvature
-secreted/maintained by corneal endothelial cells
will thicken with age
layer 5/6
endothelium
cornea
simple squamous
resp for metabolic exchanges of cornea + removes xs fluid from stroma
layer 6/6
iris
vascular layer
contractile diaphragm w/ central aperture (pupil) ant to lens via sphincter and dilator pupilae
reg amount of light passing into eye
pupillae muscles
iris
- sphincter = constricts pupil via parasymp inn, in bright light
- dilator = dilates pupil via symp inn, in dim light
layers of iris
- stroma= vascular, loose CT, melanocytes (eye color) + sphincter pupillae
- pigment epithelium/PE = 2 rows of cuboidal cells (ant row is myoepithelium/basal row of dilater pupillae)
ciliary body
ciliary muscle + ciliary processes
muscle = sphincter muscle w/ parasymp inn, does accomodation
processes= zonular fibers/suspensory ligs, lined w/ ciliary epithelium that secretes zonular fibers + aq humor
accomodation
contract ciliary muscle = relax suspensory lig > lens to round for near vision
relax ciliary muscle = tension on suspensory lig > flatten lens for far vision
ciliary epithelium
of ciliary body
double layer of cuboidal cells but only outer is pigmented
continuous w/ pigment epithelium of iris and nonphotosensitive retina
choroid
@ b/t retina and sclera
heavily pigments and vascularized
layers:
1. choriocapillary = vascular layer for blood to outer layers of retina
2. bruch’s membrane = fimly attach to RPE of retina
retina layers
- outer = RPE
- inner = neural/retina proper w/ photosensitive cells + neurons
retina regions
- anterior = nonphotosensitive
- posterior = photosensitive
divided by ora serrata (marks ant extent of visual retina and choroid)
fovea centralis
retina
area of highest visual activity bc highest density of cones NO RODS
-conducting and association neurons deflected =maximal light penetration
surrounded by macula lutea (yellow color, ganglion cell layer thickest)
optic disc
where optic nerve pierces retina
no photorecptors so blind spot
central artery/vein enter then travels w/ nerve fiber layer for inner layers of retina
age related macular degeneration
loss of photoreception in macula lutea = loss of central vision, peripheral vision unaffected
dry AMD = most common, drusen disrupts retina OR wet AMD = neovascularization
light pathway
general
light thru all 10 layers (photosens in outer + optic nerve fibers in inner) to reach rods/cones
nerve impulse passed back thru layers to optic nerve fibers in inner lyaer
neural retina cell types
- association neurons = horizontal + amacrine
- conducting = bipolar + ganglion
- supporting = muller’s cells
- photosensitive cells = rods and cones
association neurons
reg neural impulses aka quality control via filtering, facilitate impulses b/t cell layers
horizontal and amacrine
conducting neurons
transmission of visual impulses toward brain
bipolar and ganglion (multipolar)
supporting cells
provide structural and physiological support
muller cells- cytoplasm spans thickenss of entire neural retina layers
photosensitive cells
react w/ light
rods and cones
10 layers of retina
- RPE
- rods and cones
- outer limiting membrane
- outer nuclear layer
- outer plexiform layr
- inner nuclear layer
- inner plexiform layer
- ganglion cell layer
- optic nerve fibers
- inner limiting membrane
RPE
-single layer cuboidal cells w/ microvilli that surround rods/cones + have melanin granules
-melanin absorbs light, prevents reflection
-maintain blood-retina barrier
-phagocytosis and disposal of shed discs
-store/supply vitamin A
retinal detachment b/t microvilli and R/C bc not solid
rod and cone structure
- inner segment = metabolic machinery
- outer segment = site of photosensitivty, numerous rods + some cones
retinal detachment
b/t RPE and layer of rods/cones
RPE strongly attach to bruch membrane and choroid but not to neural retina bc of development layers
from trauma or disease, treat w/ surgery if not then blindness
rods
most numerous and sens to light
-rhodopsin pigment reacts w/ light and dep on vitamin A
black and white vision
discs are sep from plasma membrane
cones
less numerous than rods except in fovea, discs connect to plasma membrane
3 types:
1. red (long wavelengths)
2. green (medium)
3. blue (short)
photopsin pigment reacts w/ light
color blindness
red-green confusion from
1. deuteranopia (loss M/green cones) OR
2. protanopia (loss L/red cones)
-both sex linked X chromo
blue-yellow confusion from tritanopia (loss S/blue cones) autosomal chromo 7
limiting membranes
retina layers
layer #3 = outer, not true membrane, apical boundary of muller cells
layer #10 = inner, basal lamina of muller cells, sep retina from vitreous body
nuclear layers
retina layers
4 = outer, nuclei of photosensitive cells aka rods/cones
#6 = inner, everything else (horizontal, amacrine, bipolar, muller)
#8 = ganglion cells, nuclei of ganglion cells (form optic nerve), absent in fovea centralis
plexiform layers
5 = outer, proceses of photosensitive + bipolar + horizontal cells
visual processing
- rods/cones react to light
- pass info to bipolar cells
- horizontal cells inhibit bad data
- bipolar pass info to ganglion cells
- amacrine cells inhibit bad data
- central processes of ganglion form optic nerve to transmit visual info to brain
- muller cells provide structure/metabolic support for other retinal cells, form inner and outer limiting membranes
