Sensory Systems - Eye Flashcards
(62 cards)
1
Q
describe layers of orbit
A
- outer fibrous coat = cornea, sclera
- middle vascular (uveal) coat = iris, ciliary body, choroid
- inner retinal coat = retinal pigmented epithelium and neural retina
2
Q
describe chambers of the eye
A
3 chambers:
- anterior (b/w cornea and iris)
- posterior (b/w back of iris and lens w/ attached fibers)
- vitreous cavity (b/w lens and retina)
3
Q
generally describe the cornea
A
- transparent
- convex
- avascular (no blood or lymph in central portion)
- 5 layers
- can be transplanted w/o rejection
4
Q
fxn of the convex shape of the cornea
A
aid in focusing light and images on retina
5
Q
how do the central and peripheral parts of the cornea get nutrients?
A
central: diffusion from aqueous humor
peripheral: blood from limbus vessels
6
Q
name the 5 layers of the cornea
A
- epithelium
- Bowman’s layer/membrane
- stroma
- Decemet’s membrane
- corneal endothelium
7
Q
describe epithelium of cornea
A
- anterior layer
- non-keratinized stratified squamous
- small microvilli
- pain receptors (trigeminal and oculomotors)
- can regenerate
8
Q
describe Bowman’s layer/membrane of cornea
A
- layer of type 1 collagen
- cannot regenerate
- part of stroma
9
Q
describe stroma of cornea
A
- lattice of type 1 and type 5 collagen
- ECM rich in chondroitin and keratan sulfate
10
Q
describe Decemet’s membrane of cornea
A
- thick (5-10 um) basement membrane
- contains type 7 collagen
- produced by corneal endothelium
11
Q
describe corneal endothelium
A
- surface faces anterior eye chamber
- impermeable intercellular spaces that prevent fluid leakage into corneal stroma
12
Q
generally describe the sclera
A
- dense irregular CT
- opaque
13
Q
function of sclera
A
- protection and structural support
- insertion point for extraocular muscles
14
Q
what is the limbus?
A
corneoscleral junction
15
Q
what is adjacent to the limbus?
A
trabecular meshwork and canal of Schlemm
16
Q
describe aqueous humor
A
fluid resembling plasma, but w/ less protein
17
Q
what produces aqueous humor?
A
ciliary body epithelium
18
Q
describe flow of aqueous humor
A
anterior chamber -> trabecular network -> canal of Schlemm -> aqueous veins -> episcleral veins
19
Q
what does obstruction of aqueous humor flow lead to?
A
increased pressure in eye -> glaucoma
20
Q
describe the choroid and fxn
A
- highly vascular nutrient supplier to all eye layers
- contains melanin
- 3 layers
21
Q
3 layers of the choroid
A
- Bruch’s membrane
- choriocapillaris (fenestrated caps-supply retina, fovea)
- choroidal stroma
22
Q
what does the ciliary body consist of?
A
uveal and neuroepithelial portions
23
Q
describe uveal portion of ciliary body
A
- outer layer of choroid (supraciliaris) + ciliary muscle attached to suspensory ligament
- layer of fenestrated capillaries
24
Q
describe neuroepithelial portion of ciliary body
A
2 layers of ciliary epithelium:
- outer pigmented layer continuous w/ retinal pigmented epithelium
- inner non-pigmented layer
25
what does the anterior portion of the ciliary body form?
it is folded to form ciliary processes
26
what does epithelium in the ciliary processes produce?
aqueous humor
27
what is the iris?
- continuation of the ciliary body
| - anterior part of middle coat (uvea)
28
what controls size of pupil?
smooth muscle in iris
29
describe smooth muscle in iris
2 layers:
- circular (sphincter - parasympathetic)
- radial (dilator - sympathetic)
30
describe the lens
- avascular
- transparent
- elastic
- biconvex
31
what encloses the lens?
capsule - thick basement membrane like material
32
how does the lens change shape?
changes shape when tension on suspensory ligament fibers (zonular fibers) changes
33
what is vitreous humor?
- gel-like, transparent
- water + hyaluronic acid
- fills vitreous chamber
34
function of vitreous humor
keeps lens and retina in place
35
what is a cataract?
opacity of lens - associated with aging
36
first two layers of retina
1. retinal pigmented epithelium (RPE)
| 2. layer of rods and cones (photoreceptors)
37
describe RPE fxns (3)
- absorbs scattered light rays
- phagocytosis of worn out discs shed from rods
- stores and releases vitamin A to photo receptors
38
what is the clinical significance of the RPE?
closely adhered to choroid - trauma can dislodge the retina at this site (where there is a space b/w RPE and rest of retina)
39
what are rods: describe cells, contents, fxn?
- tall cylindrical cells
- outer segments = modified cilia
- have discs from plasma membrane w/ rhodopsin pigment (transducer of light energy)
- fxns in low light and peripheral vision
40
what are cones: describe cells, contents, fxn?
- shorter cone shaped cells
- outer segments = modified cilia
- have discs and pigments sensitive to red, green, and blue light
- fxn in color vision and bright light
41
where are cones found in relation to rods?
cones are located more centrally than rods
42
what photoreceptors are found in the fovea?
only cones
43
describe renewal of photoreceptors
1. outer discs of old rods shed into space b/w outer segments and RPE, which phagocytoses them.
2. new discs made from below, move upward, and replace old ones.
cone discs shed and replaced more slowly
44
what are the posterior retina landmarks?
macula lutea and optic disc - viewed through the pupil by a scope
45
what is the optic disc?
papilla where the optic nerve fibers exit retina
46
does the optic disc have photoreceptors?
no
47
fovea: what is it, fxn, describe photoreceptors?
what: a pit in the center of the macula
fxn: important for visual acuity
photoreceptors: only cones, very closely packed - highly represented in optic nerve and visual cortex = macular vision
48
describe vessels around macula
- no retinal vessels
| - abundant choroid vessels on outside
49
what is detached retina?
neural retina separated from RPE and from choroidal capillaries which feed photoreceptors, especially in fovea
50
what is age related macular degeneration?
macular area and fovea lose function due to pigment epithelium behind retina degenerating and forming drusen (white spots) -> allowing fluid leakage behind fovea
51
what type of vision loss does age related macular degeneration cause?
foveal cones die -> central vision loss -> cannot read or see fine detail
52
what is a leading cause of blindness?
age related macular degeneration
53
what is a common eye problem in aging?
glaucoma - increased pressure w/i eye
54
what causes high intraocular pressure in glaucoma?
anterior chamber cannot exchange fluid properly by normal aqueous outflow
55
what does the increased pressure in glaucoma lead to?
compromises blood vessels of optic nerve and axons of ganglion cells
56
retinitis pigmentosa: what is it, what is first sign of disease, what develops eventually?
- rods of peripheral retina degenerate in early stages of disease
- first sign of disease = night blindness
- eventually develop tunnel vision
- black pigment in peripheral retina and thinned blood vessels at optic nerve head
57
what is spared in retinitis pigmentosa?
only fovea
58
how do you get retinitis pigmentosa?
hereditary
59
how do you treat retinitis pigmentosa?
no cure
60
what is diabetic retinopathy?
eye blood vessels become distorted and multiply
61
how do you treat diabetic retinopathy?
laser treatment to stop blood vessel proliferation and fluid leakage
62
what is hereditary retinal dystrophy?
inability of RPE to phagocytize worn out discs from rods
