Chapter 17: Sense Organs: The Eye and the Ear

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accommodation

Normal adjustment of the eye to focus on objects from far to near.

anterior chamber

Area behind the cornea and in front of the lens and iris. It contains aqueous humor.

aqueous humor

Fluid produced by the ciliary body and found in the anterior chamber.

humor

Any body fluid, including blood and lymph

biconvex

Consisting of two surfaces that are rounded, elevated, and curved evenly, like part of a sphere. The lens of the eye is a biconvex body.

choroid

Middle, vascular layer of the eye, between the retina and the sclera.

ciliary body

Structure surrounding the lens that connects the choroid and iris. It contains ciliary muscles, which control the shape of the lens, and it secretes aqueous humor.

cone

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

conjunctiva

Delicate membrane lining the undersurface of the eyelids and covering the anterior eyeball.

cornea

Fibrous transparent layer of clear tissue that extends over the anterior portion of the eyeball.

fovea centralis

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

fundus of the eye

Posterior, inner part of the eye.

iris

Pigmented layer that opens and closes to allow more or less light into the eye. The central opening of the iris is the pupil.

lens

Transparent, biconvex body behind the pupil of the eye. It bends (refracts) light rays to bring them into focus on the retina.

macula

Yellowish region on the retina lateral to and slightly below the optic disc; contains the fovea centralis, which is the area of clearest vision.

optic chiasm

Point at which optic nerve fibers cross in the brain (chiasm means crossing).

optic disc

Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light.

optic nerve

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

pupil

Central opening of the eye, surrounded by the iris, through which light rays pass. It appears dark.

refraction

Bending of light rays by the cornea, lens, and fluids of the eye to bring the rays into focus on the retina.

retina

Light-sensitive nerve cell layer of the eye containing photoreceptor cells (rods and cones).

rod

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

sclera

Tough, white outer coat of the eyeball.

thalamus

Relay center of the brain. Optic nerve fibers pass through the thalamus on their way to the cerebral cortex.

vitreous humor

Soft, jelly-like material behind the lens in the vitreous chamber; helps maintain the shape of the eyeball.

aque/o

water

blephar/o

eyelid

conjunctiv/o

conjunctiva

cor/o

pupil

corne/o

cornea

cycl/o

ciliary body or muscle of the eye

dacry/o

tears, tear duct

irid/o

iris

kerat/o

cornea

lacrim/o

tears

ocul/o

eye

ophthalm/o

eye

opt/o

eye, vision

optic/o

eye, vision

palpebr/o

eyelid

papill/o

optic disc; nipple-like

phac/o

lens of the eye

phak/o

lens of the eye

pupill/o

pupil

retin/o

retina

scler/o

sclera; hard

uve/o

uvea; vascular layer of the eye

vitre/o

glassy

ambly/o

dull, dim

dipl/o

double

glauc/o

gray

mi/o

smaller, less

mydr/o

widen, enlarge

nyct/o

night

phot/o

light

presby/o

old age

scot/o

darkness

-opia

vision

-opsia

vision

-tropia

to turn

astigmatism

Defective curvature of the cornea or lens of the eye.

hyperopia (hypermetropia)

Farsightedness

myopia

Nearsightedness

presbyopia

Impairment of vision as a result of old age.

cataract

Clouding of the lens, causing decreased vision.

chalazion

Small, hard, cystic mass on the eyelid

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

nystagmus

Repetitive rhythmic movements of one or both eyes.

blepharitis

Inflammation of the eyelid, causing redness, crusting, and swelling along lid margins.

dacryocystitis

Blockage, inflammation, and infection of a nasolacrimal duct and lacrimal sac, causing redness and swelling in the region between the nose and the lower lid.

ectropion

Outward sagging and eversion of the eyelid, leading to improper lacrimation and corneal drying and ulceration.

entropion

Inversion of the eyelid, causing the lashes to rub against the eye; corneal abrasion may result.

ptosis

Drooping of upper lid margin as a result of neuromuscular problems or trauma

xanthelasma

Raised yellowish plaque on eyelid caused by lipid disorder

retinal detachment

Two layers of the retina separate from each other.

strabismus

Abnormal deviation of the eye

fluorescein angiography

Intravenous injection of fluorescein (a dye) followed by serial photographs of the retina through dilated pupils.

ophthalmoscopy

Visual examination of the interior of the eye

slit lamp microscopy

Examination of anterior ocular structures under microscopic magnification

visual acuity test

Clarity of vision is assessed

visual field test

Measurement of the area (peripheral and central) within which objects are seen when the eyes are fixed, looking straight ahead without movement of the head.

enucleation

Removal of the entire eyeball

keratoplasty

Surgical repair of the cornea

laser photocoagulation

Intense, precisely focused light beam (argon laser) creates an inflammatory reaction that seals retinal tears and leaky retinal blood vessels.

LASIK

Use of an excimer laser to correct errors of refraction (myopia, hyperopia, and astigmatism). LASIK is an acronym for LASer In situ Keratomileusis.

phacoemulsification

Ultrasonic vibrations break up the lens, which then is aspirated through the ultrasonic probe.

scleral buckle

Suture of a silicone band to the sclera over a detached portion of the retina.

vitrectomy

Removal of the vitreous humor.

auditory canal

Channel that leads from the pinna to the eardrum.

auditory meatus

Auditory canal

auditory nerve fibers

Carry impulses from the inner ear to the brain (cerebral cortex). These fibers compose the vestibulocochlear nerve (cranial nerve VIII).

auditory tube

Channel between the middle ear and the nasopharynx; eustachian tube.

auricle

Flap of the ear; the protruding part of the external ear, or pinna.

cerumen

Waxy substance secreted by the external ear; also called earwax.

cochlea

Snail-shaped, spirally wound tube in the inner ear; contains hearing-sensitive receptor cells.

endolymph

Fluid within the labyrinth of the inner ear

eustachian tube

Auditory tube

incus

Second ossicle (bone) of the middle ear; incus means anvil.

labyrinth

Maze-like series of canals of the inner ear. This includes the cochlea, vestibule, and semicircular canals.

malleus

First ossicle of the middle ear; malleus means hammer.

organ of Corti

Sensitive auditory receptor area found in the cochlea of the inner ear.

ossicle

Small bone of the ear; includes the malleus, incus, and stapes.

oval window

Membrane between the middle ear and the inner ear

perilymph

Fluid contained in the labyrinth of the inner ear.

pinna

Auricle; flap of the ear

semicircular canals

Passages in the inner ear associated with maintaining equilibrium

stapes

Third ossicle of the middle ear. Stapes means stirrup.

tympanic membrane

Membrane between the outer and middle ear; also called the eardrum

vestibule

Central cavity of the labyrinth, connecting the semicircular canals and the cochlea. The vestibule contains two structures, the saccule and utricle, that help to maintain equilibrium.

acous/o

hearing

audi/o

hearing; the sense of hearing

audit/o

hearing

auricul/o

ear

cochle/o

cochlea

mastoid/o

mastoid process

myring/o

eardrum, tympanic membrane

ossicul/o

ossicle

salping/o

eustachian tube, auditory tube

staped/o

stapes

tympan/o

eardrum, tympanic membrane

vestibul/o

vestibule

-acusis

hearing

-cusis

hearing

-meter

instrument to measure

-otia

ear condition

acoustic neuroma

Benign tumor arising from the acoustic vestibulocochlear nerve (eighth cranial nerve) in the brain.

cholesteatoma

Collection of skin cells and cholesterol in a sac within the middle ear.

deafness

Loss of the ability to hear.

Meniere disease

Disorder of the labyrinth of the inner ear; elevated endolymph pressure within the cochlea and semicircular canals.

otitis media

Inflammation of the middle ear.

otosclerosis

Hardening of the bony tissue of the middle ear.

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.

audiometry

Testing of the sense of hearing.

cochlear implant procedure

Surgical insertion of a device that allows sensorineural hearing-impaired persons to understand speech

ear thermometry

Measurement of the temperature of the tympanic membrane by detection of infrared radiation from the eardrum.

otoscopy

Visual examination of the ear canal with an otoscope.

tuning fork test

Test of ear conduction using a vibration source (tuning fork)

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