Vision Flashcards
Eyelids
separated by the palpebral fissure
meet at medial and lateral angles (canthi)
lacrimal caruncle
reddish elevation at the medial canthus
tarsal plates
connective tissue within the eyelids
Levator palpebrae superopris muscle
moves upper eyelid
conjenctiva
transparent mucous membrane
larimal apparatus
keeps the surface of the eye moist. lacrimal gland larimal punctum larimal canaliculus lacrimal sac- fluid empties into nasal cavity nasolacrimal duct inferior meatus
Eye Muscles
lateral rectus- lateral-abducens
medial rectus-medial-oculomoter
superior rectus- elevates, medial turn- oculomotor
inferior rectus- depresses, medial turn- oculomotor
inferior oblique- elevates, lateral turn- oculomotor
superior oblique- depresses, lateral turn- trochlear
Posterior Segement of Eye
divided by ciliary zone and lens filled with vitreous humor- clear jelly like transmits light supports posterior surface of the lens helps maintain intraocular pressure
Anterior Segment of Eye
contains both anterior and posterior chambers
anterior chamber- between the cornea and iris
posterior chamber- between iris and lens
both filled with aqueous humor
Glaucoma
increased pressure in anterior segement due to slow draining aqueous humor. causes compression of retina and optic nerve
Lens
thick transparent, biconvex disc
held in place by ciliary zonule
elongated lens fibers form bulk of lens
lens gets bigger throughout life
Light bending structures
lens, cornea, humors
accomodation
curvature of the lens is adjustable which allow focusing on nearby objects
Wall of eye- fiborous layer
most external
dense connective tissue
sclera and cornea
sclera
posterior 5/6 of the tunic
white region
provides shape and anchor for the eye muscles
cornea
anterior 1/6 of eye connected to sclera by the limbus has epithelium and endothelium avascular but gets O2 from environment many sensory nerves, much are pain receptors
scleral venous sinus
allows aqueous humor to drain
Wall of eye- vascular layer
middle layer
choroid
cilliary body
iris
choroid
vascular
dark pigmented
posterior 5/6 of vascular tunic
brown
prevents scattering of light rays within the eye
choroid corresponds to the arachnoid and pia maters
Ciliary Body
thickened ring of tissue which encircles the lens
mainly smooth muscle that focuses lens
made of :
ciliary processes and ciliar zonule (suspensory ligament- halo of fine fibers around lens)
Iris
colored part
smooth muscle, attached to ciliary body
pupil
round central opening
sphincter pupillae muscle (circular)
dilator pupillae muscle (radial)
Wall of Eye- inner layer
retina
optic nerve
Retina
deepest. 2 layers: pigemented- outer neural- inner, has nervous tissue photoreceptor cells, bipolar cells and ganglia (acramine and horizontal sometimes)
macula lutea
contains mostly cones
fovea centralis
only cones. visual acuity
optic disc
blind spot
rods & cones
rods- sensitive to light cones- color both have 2 segments outer- receptor region inner- generate nerve impulse
Visual pathway to cerebral cortex
optic nerve–> optic chiasm–> optic tract–> lateral geniculate nucleus of thalamus–> optic radiation–> primary visual cortex
visual pathways to other parts of the brain
midbrain:
superior conlliculi: controls extrinsic eye muscles
pretectal nuclei: mediate pupillary eye reflexes
suprachiasmatic nucleus
Blood supply to retina
outer 1/3 gets it from caps in choroid
inner part gets it from central artery
cataracts
lens becomes opaque. people over 50
macular degeneration
buildup of deposits in the retina causing loss of vision in the macula which is the center of the visual field
trachoma
contagious infection from chlamydia of conjunctiva. causes the eyelids to become distorted and inverted causing eyelashes to scrape against cornea. leads to scarring and blindness.
