LOM Ch. 17 Sense Organs: The Eye and the Ear

pupil

central dark opening of the eye where light enters the eye

Iris

Colored part of the eye

conjuctiva

the mucous membrane that covers the front of the eye and lines the inside of the eyelids.

it is clear and almost colorless except when blood vessels are dialated

Cornea

is a fibrous, transparent tissue that extends like a dome over the pupil and iris, thus light passes thru the cornea before it enters the pupil

-the purpose of the cornea is to bend, or refract the rays of light

Refraction

Bending of rays as they pass through the cornea,lens, and other tissues

accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina

aqueous humor

fluid produced by the ciliary body and found in the anterior chamber

function is to help maintain shape of the anterior of the eye and nourish this area

vitreous humor

jellylike substance found behind the lens in the posterior cavity of the eye that maintains its shape

this substance is not constantly reformed, if there is vitreous humor substance lost it could result in retinal damage or blindness

anterior chamber of eye

behind the cornea and in front of the iris, it contains aqueous humor

Retina

the light-sensitive nerve cell layer of the eye containing the photoreceptor cells (rods and cones) plus layers of neurons that begin the processing of visual information

rods and cones

two types of photoreceptors in the retina

optic nerve

cranial nerve carrying impulses from the retina to the brain(cerebral cortex)

Sclera

tough, white outer coat of the eyeball

fovea centralis

tiny pit or depression in the retina that is the region of clearest vision

cone

Photoreceptor cell in the retina that transforms light energy into a nerve impulse. Cones are responsible for color and central vision.

Rods

Photoreceptor cell of the retina essential for vision in low light and for peripheral vision

aque/o

water

blephar/o

eyelid

cor/o

pupil

corne/o

cornea

dacry/o

tears, tear duct

ir/o, irid/o

iris (colored portion of the eye around the pupil)

kerat/o

cornea

Lacrim/o

tear

ocul/o

eye

ophthalm/o

eye

opt/o, optic/o

eye, vision

palpebr/o and blephar/o

eyelid

scler/o

sclera, white of eye, hard

astigmatism

defective curvature of the cornea or lens of the eye

hyperopia (hypermetropia)

farsightedness

myopia

nearsightedness

cataract

clouding of the lens of the eye, causing impairment of vision

diabetic retinopathy

retinal effects of diabetes mellitus include microaneurysms, hemorrhages, dilation of retinal veins, and neovascularization (new blood vessels form in the retina)

Glaucoma

increased intraocular pressure results in damage to the retina and optic nerve with loss of vision

hordeolum (stye or sty)

localized, purulent, inflammatory staphylococcal infection of a sebaceous gland in the eyelid

macular degeneration

progressive damage to the macula of the retina

retinal detachment

two layers of the retina separate from each other

patients often experience photopsia(bright flashes of light) and floaters (black spots or filmy shapes)

strabismus

abnormal deviation of the eye

3 parts of the ear

outer ear, middle ear, inner ear

acoustic neuroma

benign tumor on the auditory nerve (8th cranial nerve) that causes vertigo, tinnitus, and hearing loss

Meniere's disease

Abnormal condition within the labyrinth of the inner ear that can lead to a progressive loss of hearing. The symptoms are dizziness or vertigo, hearing loss, and tinnitus (ringing in the ears). attacks last minutes or continue for hours, those who suffer may need prolonged bed rest, sedation, medications to combat nausea and possibly surgery

otitis media

inflammation of the middle ear, commonly in children as a result of infection

otosclerosis

hardening of the bony tissue of the middle ear

it is a hereditary condition

tinnitus

sensation of noises (ringing, buzzing, whistling, booming) in the ears

vertigo

sensation of irregular or whirling motion either of oneself or of external objects

those who suffer often have bouts with nausea