Eye Histology Flashcards
anterior compartment
contains the anterior and posterior chambers separated by iris
filled with aqueous humor
posterior compartment
posterior 2/3
contains vitreous humor (with proteins and hyaluronic acid, hyalocytes)
coreo-scleral layer
fibrous tunic that makes up globe of the eye (makes up sclera)
where EOM insert, conjunctiva
high collagen and elastin
nearly avascular
Uveal layer
vascular layer, contains the iris, highly pigmented, contains blood vessels
Posterior: called choroid
Anterior: cilliary body (contains smooth mm. for accommodation)
Conjunctiva
stratified columnar epithelial extension of the sclera
lines the anterior surface of eyeball and inner surface of eyelid
contains mucus secreting goblet cells
cornea
transparent in the anterior eye
avascular, highly innervated
5 layers
5 layers of cornea
1) outer epithelium (NK Squamous)
2) Bowman’s membrane (basal lamina)
3) Substantia propria: dense collagenous tissue with keratinocytes (allows tissue to remain clear)
4) Descemet’s membrane: thick BL (attachment for corneal epithelium)
5) Corneal endothelium
Corneal endothelium
attached to thick basal lamina essential for the movement of nutrients, water, and ions into the cornea from aq humor
important for healing (lots of stem cells)
Myopia
nearsightedness
light rays are focused in front of retina
cornea is too curved or lens is too powerful for length of globe
Hyperopia
farsightedness
light rays are focused behind the retina, lens and cornea too weak for length of globe
LASIK
laser assisted in-situ keratomileusis
for myopia, hyperopia, and astigmatism
goal is to change the shape of the cornea by changing the stroma (substantia propria)
Need to not cut into stroma or Bowman’s membrane
choroid
part of the uveal layer
posterior pigmented portion of the vascular layer
loose CT, fibroblasts melanocytes (absorbs any extra light)
Bruch’s membrane
separates choroid from retina
basal lamina for pigmented epithelium of retina
controls movement of nutrients and waste
choriocapillaris
area next to retina, rich in capillaries
under Bruch’s membrane
Drussin
amyloid substance deposited bw bruchs membrane and the retina
age related macular degeneration
impedes flow of nutrients from choriocapillaris
ciliary body
wedge shaped structure, forward continuation of the uveal layer
loose CT, muscular tissue, non-pigmented epithelium
ciliary processes are attachment for zonule fibers which attach to lens
ciliary processes
important for the filtering of aq humor into posterior compartment (from nonpigmetned fibers)
allow for attachment of zonule fibers
accommodation
2 of the 3 bundles
as ciliary mm contract, ciliary body stretches, releasing tension on suspensory ligaments, lens gets thicker and more convex, focuses on nearby objects
circulation of aqueous humor
produced by ciliary epithelium lining the ciliary processes
water follows the active transport of ions into the ciliary channel (bw the apical domains of non-pigmented and pigmented ciliary epithelial cells_)
circulation of aq humor
enters posterior chamber, passes thru the papillary aperture bw the iris and lens and enters the anterior chamber
drains thru the trabecular meshwork into the canal of schlemm and directly into venous circulation
Glaucoma
optic neuropathy resulting in loss of vision due to retinal ganglion cell death
**increased intraocular pressure due to decreased flow thru canal of schlemm into venous drainage
corneal irideal angel
Descemets membrane of cornea and anterior surface of iris
allows for flow of aq humor into the canal of schlemm (which forms a complete circle here)
open angle glaucoma
NO anatomical obstruction (CI angle is open)
still increased IOP (maybe due to inc production or decreased outflow)
causes slow neurodegenerative processes, optic n cupping
tx: increase outflow or decreasing production
angle closure claucoma
CI angle is closed
aq outflow is prevented
primary, congential cause
secondary: due to inflammation, hemorrhage, tumor
**conjunctival redness
Iris
colored, anterior extension of ciliary body
controls pupillary aperture
separates anterior and posterior chambers
pupillary zone and ciliary zone (outer circle)
histology of iris
NO epithelium
anterior surface is stroma of fibroblasts and melanocytes (pigmentation)
highly vascularized with contractile muscles (sphincter pupillae)
lens
transparent, biconvex, avascular
on outside there is a thick, a-cellular capsule
Lens epithelium on anterior ONLY
lens fibers
elongated fibers (from epithelium) shape and components depend on location on position
anteriorly, they are long, a-nucleate sacks of crystalline proteins which allows for transparency based upon their solubility
cataract
leading cause of blindness
lens does not shed non-viable lens fibers-NO APOPTOTIC MECHANISM (become more compact as we age)
Related to oxidative injury (ETOH, sunlight, hyperglycemia….)
tx: surgical replacement with synthetic intraocular lens
