Eye Flashcards
(44 cards)
1
Q
Fibrous tunic
A
Outer layer. Sclera, cornea (scelera is continuous with cornea)
2
Q
Vascular tunic
A
Middle layer. Mostly choroid, also ciliary body, iris anteriorly
3
Q
Neural tunic
A
Retina; inner layer.
retinal pigment epithelium (outer), neural retina (inner) (fovea and optic disc, blood supply from central retinal artery)
4
Q
Extraocular muscles
A
attach outside of sclera to socket
5
Q
Sclera
A
- white part of eye on outside.
- Continuous with cornea.
- sensory innervation
- vascularized
- serves as protective envelope for internal eye
6
Q
Choroid
A
- Posterior portion of vascular tunic.
- loose CT
- highly vascularized (nutrients to retinal pigment epithelium and outer layers of neural retina) and pigmented
7
Q
Ora serrata
A
Point at which photosensitive retina ends
8
Q
3 layers of the eye
A
Fibrous tunic (outer), vasclar tunic (middle), neural tunic (inner)
9
Q
Composition of sclera
A
- thick dense CT.
- mostly type I collagen (oriented in all directions) and few elastic fibers.
- contains elongated fibroblasts
10
Q
Cornea
A
- transparent
- avascular (gets nutrients from aqueous humour and lacrimal fluid(
- highly innervated
- important in light refraction
- 5 layers
11
Q
5 layers of cornea
A
- corneal epthelium
- Bowman’s membrane
- stroma
- descemet’s membrane
- corneal endothelium
12
Q
corneal epithelium
A
- stratified squamous non keritinized epithelium (5-7 layers)
- turnover rate ~7 days
- highly innervated
13
Q
Bowman’s membrane
A
basement membrane
14
Q
Stroma
A
- ~90% of corneal thickness
- type I collagen ( mostly) and few elastic fibers and fibroblasts
- lamella organization of this layer important in cornea transparency (think layers of plastic wrap vs. scrunched up ball of plastic wrap)
15
Q
Descemet’s membrane
A
basement membrane of cornea
16
Q
corneal endothelium
A
-simple squamous layer, lines posterior surface of the cornea
17
Q
Conjunctiva
A
- mucous membrane covering anterior sclera and lines inside of eyelid
- stratified columnar epithelium containing goblet cells
18
Q
Goblet cells
A
secretions contribute to tear film
19
Q
Conjunctivitis
A
AKA pink eye
- inflammation of conjunctiva
- caused by bacteria or virus, very contagious.
- also caused by allergens or irritants (smoke, chlorine, etc)
20
Q
Ciliary body
A
- wedge shaped region of vascular tunica
- loose CT
- rich in blood vessels and smooth muscle
- double layer of cuboidal epithelium (pigmented and non pigmented layer)
- produces aqueous humour
- changes shape of lens
21
Q
Ciliary processes
A
- fenestrated capillaries
- plasma filtrate transported across epithelium as aqueous humour
22
Q
Aqueous humour
A
- provides nutrients to lens and cornea (also pressure makes cornea bulge)
- enters posterior chamber to pupillary aperature to anterior chamber then leaves through canal of Schlemm (reticular network, not canal)
23
Q
Glaucoma
A
increased intraocular pressure caused by failure of resporption of aqueous humour. Leads to comprimised retinal blood flow and retinal damage. Untreated can cause blindness
24
Q
Zonule fibers
A
-radiate from ciliary body and insert into the lens capsule forming suspensory ligament of lens
25
Contraction vs relaxation of ciliary body
Contraction: reduces tension on zonule fibers and makes lens convex. Eye focuses on near objects. Accomodation
Relaxation: increases tension on zonule fibers and lens flattens. Eye focuses on far objects.
26
Accomodation reflex
Change of lens shape from looking at distant object to close object
27
Iris
- anterior extension of vascular tunic
- posterior surface has pigmented cells which block light from passing through iris
- anterior surface has pigmented cells (also in stroma) which make eye colour (dark eyes high pigmented, blue eyes low pigment)
28
Stroma of iris
- contains smooth muscle
- dilator pupillae (radially oriented) and sphincter papillae (circumferentially oriented) muscles control pupillary aperature
29
Lens
- biconvex (), transparent disc for focussing light
| - 3 parts: lens capsule, subcapsular epithelium, lens fibers
30
Lens capsule
basement membrane, completely envelopes the lens
31
Subcapsular epithelium
single layer of cuboidal cells only on anterior surface of lens. At equators, subcapsular epithelium give rise to lens fibers.
32
Lens fibers
- Immediately deep to subcapsular epithelium.
- 2000-3000 elongated cells called lens fibers make up bulk of lens (go anterior-posteriorly)
- generated at equator and continue at slow rate through life
- during maturation, elongate, lose nuclei and organelles, and become filled with crystallins (proteins)
33
Cataract
opaque lens
34
Vitreous body
- transparent, refractile gel filling vitreous cavity behind the lens
- 99% water, also collagen fibers and hyaluronic acid
- small amount of phagocytic cells
35
Hyalocytes
- at periphery of vitreous body in small amount.
| - Synthesize collagen and hyaluronic acid.
36
Composition of retina
Inside-> outside
inner limiting membrane, ganglion cell (axons then cell body), Inner plexiform layer (synaptic zone), inner nuclei layer (Muller cell (supporting glial cell), amacrine cell, bipolar cell, horizontal cell) outer plexiform layer (synaptic zone), outer nuclear layer (rods and cones cell bodies), outer limiting membrane, photoreceptor layer (rods, cones), pigment cells (RPE)
37
Retinal pigment epithelium (RPE)
- cuboidal to columnar cells (nuclei basally located)
- apical aspects abundant in melanin granules, microvilli, and sleeve like extensions that surround tops of photoreceptor cells
- reduce light scatter by absorbing stray light
- phagocytose membrane shed from photoreceptors
38
Blood retina barrier
Made of desmosomes, zonulae occludens, and zonulae adherents in RPE
39
Photoreceptors
- rods and cones
- absorb photons causing receptor potential (processed through retinal layers before reaching the retinal ganglion cells)
40
Rods
- extremely light sensitive (good for low light)
| - monochomatic (black and white)
41
Cones
- sensitive in daylight (need more light than rods)
- trichromatic (3 opsins, red green and blue)
- relative levels of activity of different wavelength sensitive cones determines colour
42
Colourblindness
altered gene expression of one or more cone opsins (some colours cannot be discriminated)
-red green colourblindess often occur together because of proximity of gene on X chromosome
43
Fovea
- specialized region of retina for high acuity vision
- lots of cones
- several retinal layers missing in fovea, instead around edge
44
Optic disc
- exit point of retinal ganglion cell axons
- unmylinated retinal ganglion cell axons collect here, pierce sclera, become mylinated and form optic nerve
- no photoreceptors here so forms blind spot.
