eye Flashcards
external landmarks (sclera, cornea, iris, pupil)
eyelids (palpebrae)
whites of the eye
- posterior 5/6 of eye
- function: provides shape to eyeball and protects inner parts
sclera
transparent; in front of iris (center part)
- curved transparent structure anterior to iris and pupil
- anterior 1/6 of the eye
- function: admits and refracts (bends) light
cornea
pigmented part of the eye
- contains pupil
- function: regulates the amount of light entering the eye (by dilating and constricting
iris
opening in iris
pupil
lining sclera and eyelid
function: secrete mucus as lubricant for eye/eyelids
conjunctiva
inflammation of conjunctiva (“pink eye”)
conjunctivitis
produces/collects tears
lacrimal apparatus
tears
lacrimal fluid
produces and secretes tears
lacrimal gland
t/f: fluid is swept across the surface of the eye by the eyelids
true
from lacrimal puncta (hole) to nasolacrimal duct
lacrimal canaliculi
drains tears into nasal cavity, where they are eventually swallowed
nasolacrimal duct
why do tears spill onto the cheek when someone gets a runny nose?
- tears overwhelm the system (lacrimal apparatus)
- too many tears to collect - overflow the eyelids
- nasolacrimal duct pours lots of tears into nasal cavity - runny nose
moves eye medially (adducts)
- eye moves toward nose
medial rectus
moves eye laterally (abducts)
- eye moves toward ear
lateral rectus
elevates eye and moves eye medially
superior rectus
depresses eye and moves eye medially
inferior rectus
depresses and moves eye laterally
superior oblique
elevates eye and moves eye laterally
inferior oblique
what nerve innervates the medial rectus, superior rectus, inferior rectus, inferior oblique?
oculomotor nerve
what nerve innervates the superior oblique?
trochlear nerve
what nerve innervates the lateral rectus?
abducens nerve
- biconvex, transparent structure inside ball
- function: changes shape (flat or round) to focus light rays
- held in place by suspensory ligaments
lens
avascular
- contains sclera and cornea
fibrous (external) tunic
a laser removes cells from part of the cornea to change its shape - to better focus the light where needed
laser vision correction
dark brown membrane
- function: contains blood vessels that help nourish the retina
choroid
ring of smooth muscle tissue that surrounds the lens
- attaches to the lens via suspensory ligaments
- function: as the smooth muscle contracts, the suspensory ligaments relax to make the lens more round
- produces aqueous humor
ciliary body
to see close up, ciliary muscles contract, suspensory ligaments relax, and lens becomes thicker
accommodation
posterior 3/4 of eye
- one of the few places bipolar neurons can be found
- consists of pigmented and neural layer
retina
outer layer adjacent to choroid
functions:
- absorbs excess light to prevent reflection/glare
- provides vitamin a to photoreceptors
pigmented layer
inner layer
- function: its photoreceptors receive light information and convert it to nerve impulses that are sent via optic nerve (CN II) to the brain
neural layer
what are the two types of photoreceptors?
rods and cones
low (reduced) light, black and white (more than cones)
rods
require more light, color
cones
blind spot; area where the optic nerve exits the eye; contains no photoreceptors
optic disc
lateral to optic disc; in center is fovea centralis
macula lutea (yellow spot)
sharpest vision (only cones)
fovea centralis
light focused in front of retina
nearsightedness
light focused behind the retina
farsightedness
fluid collects between the pigmented layer and neural layer (can cause blindness)
detached retina
- between cornea and lens
- separated into anterior and posterior chambers by the iris
- filled with aqueous humor
anterior cavity
supplies nutrients, removes wastes for lens and cornea, and is continually produced and replaced
aqueous humor
- aqueous humor is secreted by the ciliary processes into the posterior chamber
- aqueous humor moves from the posterior chamber, through the pupil to the anterior chamber
- excess aqueous humor is resorbed via the scleral venous sinus
flow of aqueous humor
- between lens and retina
- contains vitreous humor
posterior cavity
helps maintain the shape of the eye and keeps the retina against the choroid; is not continually produced
vitreous humor
- light rays enter the eye through the cornea and are refracted (bent)
- light rays are further refracted by the lens (flattened = far vision, rounded = near)
- light rays focus on retina
- light ray information is converted to nerve impulses by photoreceptors (rods and cones)
- nerve impulses transmitted to the brain via CN II (optic nerve)
- from the optic nerves, visual information passes to the optic chiasm then to the optic tract, to the thalamus, and then to the primary visual cortex of the occipital lobe
how visual information is processed
