Lecture 23+24 +DLA 25 Flashcards
contents of the superior orbital fissure
CN III, IV, V(1), and the superior ophthalmic v.
contents of the inferior orbital fissure
V(2), zygomatic nerve, inferior ophthalmic v, infraorbital a. and v.
contents of the optic canal
CN II and ophthalmic a.
development of the eye
originally develop as a diverticulum of the forebrain neural tube
the diverticulum becomes an optic stalk and near surface ectoderm forms the optic cup
invagination of the optic cup will form the retinal fissure
development of the optic N. (II)
the optic nerve develops from the optic stalk
sclera and choroid development
both develop from mesenchyme tissue surrounding the optic cup
corneal development
corneal epithelium comes from skin ectoderm
fibrous stroma from the mesodermal capsule covering the optic cup
corneal endothelium from NCS
Iris and ciliary body development
Iris = rim of the optic cup
ciliary body = from the optic disk
hyaloid A becomes the central A of the retina
keyhole pupil
results due to the incomplete closure of the retinal fissure
defect can extend to the ciliary and retina
development of the retina
develops from two layers of the optic cup
pigment layer (outer) neural layer (inner)
development of the lens
develops from the lens vesicle (surface ectoderm)
cataracts
may be congenital due to teratogenic agents / infections
or occur later in life due to aging, trauma, radiation, etc
can be removed surgically
innervation of the eye muscles
superior oblique = trochlear n. (CN IV)
lateral rectus = abducens n. (CN VI)
all other extraocular muscles and LPS by oculomotor n. (CN III)
muscles that elevate eye
superior rectus
inferior oblique
muscles that depress or lower the eye
inferior rectus
superior oblique
Muscle testing - H test
LR, SR, IR, MR, IO, and SO
lateral rectus = abduction (out) superior rectus = out and up inferior rectus = out and down medial rectus = in inferior oblique = in and then up superior oblique = in then down
layer of the eye
- corneoscleral coat
outer fibrous layer (cornea and sclera)
2. vascular coat (uvea) middle layer (iris, ciliary body, and choroid)
- retina
inner layer
about the corneoscleral coat
anterior surface of the eye
avascular
function: refraction of light
layers of the cornea
- corneal epithelium
strat squamous
can regenerate
lots of free nerve endings
2. bowman's membrane homogenous layer of epithelium collagen fibers are random provides strength and acts as barrier to infection does NOT regenerate
3. corneal stroma corneal fibroblasts (keratocytes)
- Descemet’s membrane
meshwork of collagen fibers and pores
can regenerate
thickens as we age
5. corneal endothelium metabolic exchange regulates water (lots of Na/K pumps) simple squamous limited regeneration
histology of the sclera
thick fibrous layer (DCT)
flat collagen bundles with networks of elastic fibers
lamina cribosa: allow for entering and exiting of nerves/vessels.
the optic disk overlies this (blind spot)
3 layers of the sclera?
- external episcleral layer
loose CT - middle layer substantia propria (tenon’s capsule)
investing fascia of eye
dense network of collagen fibers
tendons attach here - inner suprachoroidal lamina
thinner collagen fibers and elastic fibers
about the vascular coat (uvea)
features: CT, blood vessels, and pigmented cells
- iris
anterior part
forms a contractile diaphragm in front of lens
pupil - ciliary body
between the iris and choroid
ciliary processes and ciliary muscle - choroid
posterior portion
lies between sclera and retina
histology of choroid
pigmented, dark brown vascular layer
functions: blood supply and absorption of scattered light.
2 layers:
- choriocapillary layer
inner vascular layer
fenestrated capillaries - Bruch’s membrane (lamina vitrea)
forms the basal lamina of RPE cells
has 5 layers
hyaline membrane
about the iris
arises from the anterior border of ciliary body
contractile diaphragm
discontinuous layer of fibroblasts and melanocytes
highly vascular Ct stroma
histology of the ciliary muscle
ciliary muscle = smooth muscle (parasympathetic)
fibers spread in all directions
histology of the ciliary processes
vascular
covered by double layer of columnar epithelium
zonular fibers = fibrillin
function:
produce and anchor zonular fibers that form the suspensory ligament of the lens
secretion of aqueous humor
part of the blood-aqueous barrier
Corneoscleral limbus (junction)
transition zone between the cornea and sclera
Bowman’s capsule ends
generate and maintain corneal epithelium
Glaucoma
increased intraocular pressure
symptoms: headache eye pain loss of vision vomiting Halo around light
signs:
vision decreases peripherally
redness
raised pressure
vitreous body
transparent jelly like substance
mainly collagen fibrils and GAGs (hyaluronan)
has spindle shaped cells = hyalocytes
maintains eye shape and keeps retina in place
change in vitreous humor and lead to retinal detachment
histology of retina
2 layers
- neural retinal (inner layer of optic cup)
non-photosensitive anterior to ora serrata
photosensitive is posterior to ora serrata - retinal pigment epithelium (RPE)
outer layer of optic cup
where does retinal detachment most likely occur?
the junction of pigment epithelial layer and the rods & cones layer
rods
cylindrical outer segment
visual pigment is rhodopsin (lack of this leads to night blindness; via no Vit A)
black and white vision
highest density outside of fovea centralis
cones
thicker and shorter than the rods
conical outer segment
visual pigment is iodopsin
color vision
largest density in fovea centralis
Retinal Pigment Epithelium
single layer of cuboidal cells
seen to have tight junctions (blood-retina barrier)
basal lamina attached to Bruch’s membrane
functions: absorption of light major component of blood-retina barrier active in visual pigment pathway vitamin A metabolism phagocytosis
histology of the lens
biconvex
avascular
held in place by the zonular fibers
3 parts:
- lens capsule
thick basal lamina
produced by anterior lens cells - subcapsular epithelium:
single layer of cuboidal cells
proliferate in the germinal layer - lens fibers
thin and flattened
loose organelles and accumulate proteins
formed by epithelial cells in the germinal layer
conjunctiva
stratified epithelium with goblet cells
lines outside of eyelid
secretes fluid into the eye
glands of the eyelid
- Meibomian glands
sebaceous within tarsal plate
delays the drying of tears - glands of Zeiss
sebaceous glands associated with the eyelashes - glands of moll
sweat glands at the lid margins
