W6_01 Eye: Anatomy and Physiology Flashcards
what divides the eye into the anterior and posterior segments?
the lens
what separates the anterior and posterior chambers?
the iris
name structures in the anterior segment of the eye
sclera cornea anterior chamber iris ciliary body lens
name the perforation in the sclera to allow optic nerve penetration
lamina cribosa; meshwork that allows passage of CN II fibres
3 components of the conjunctiva
palpebral
forniceal
bulbar
describe episclera vasculature
2 layers: superficial and deep.
deep vessels are larger
name two pathologies of the episclera
episcleritis
scleritis (serious; due to rheumatoid arthritis)
what’s the division of diopter power in the eye?
cornea: 2/3 (~40D)
lens: 1/3 (~20)
3 reasons for transparency within the cornea?
avascularity
uniform structure
deturgescence
thickness of cornea?
centrally 0.54mm;
peripherally 1 mm
how many layers of the cornea?
5
what are the layers of the cornea?
epithelium Bowman's membrane stroma Descemet's (basement) membrane endothelium
difference between cornea and sclera?
collagen is coarse and irregular in sclera, causing opacity
components of the lens?
capsule
epithelium
nucleus
cortex
types of cataracts?
cortical nuclear sclerosis (aging) posterior subcapsular (steriods, diabetes)
where can intraocular lenses be implanted?
anterior chamber
posterior chamber
components of the uvea?
iris (anterior)
ciliary body (middle)
choroid (posterior)
muscles in the iris?
sphincter muscle constricts (cholinergic)
dilator muscle dilates (adrenergic)
function of the pars plicata?
producing aqueous humour for the anterior chamber
functions of the ciliary body?
production of aqueous humour
accomodation
how is aqueous humour drained?
trabecular meshwork to canal of schlem
uveascleral outflow to episcleral venous vessels
what attaches the lens to the ciliary body?
zonules
how do the lens, ciliary bodies, and zonules change in shape to accommodation?
ciliary body SM contracts; CB moves anteriorly
zonules relax
lens rounds up
components of the posterior segment?
vitreous
retina
choroid
optic nerve
vitreous pathology?
vitreous homorrhage (e.g. diabetics) fungus endophthalmitis
how big is the optic disc?
1.5mm in diameter
what is the macula?
centre of retina;
fovea is centre of macula;
most detailed vision from here
how many layers in the retina?
how many layers does light penetrate to get to rods/cones?
- light goes through 8 layers to reach rods/cones.
choroidal pathology?
choroidal nevus
choroiditis
describe the optic nerve pathway and lengths
intraocular (1 mm)
intraorbital (25mm)
intracannalicular (9 mm)
intracranial (16 mm)
optic nerve pathology?
optic disc edema
glaucoma
7 bones that make up the orbit?
frontal sphenoid zygomatic maxillary bone lacrimal bone ethmoid bone palatine
what passes through the optic foramen? the optic foramen is in which bone?
optic nerve and opthalmic artery;
in sphenoid bone
what passes through the superior orbital fissure? the fissure is made from which bone?
CN III, IV, V1, VI, superior opthalmic vein, vessels;
fissure is between greater and lesser wings of sphenoid
layers of the tear film?
lipid layer
aqueous layer
mucin layer
corneal epithelium
what produces the mucin layer of the tear film?
conjunctival goblet cells
what produces the aqueous layer of the tear film?
accessory lacrimal glands (kraus and wolfring)
what produces the lipid layer of the tear film?
meibomian gland in lid margin
tear pathologies?
dry eye (loss of either layer)
blurry vision
can be caused by blepharitis
lacrimal gland pathology?
congenital lasolacrimal duct obstruction
dacryocystitis
