key terms

accomodation

adjustment of the eye for various distances so that images focus on the retina of the eye

acuity

clearness or sharpness of a sensory function

adnexa

tissues or structures in the body adjacent to or near a related structure

These adjacent tissues/ structures near the eye include the extra-ocular muscles, orbits, eyelids, conjunctiva, and lacrimal apparatus.

humor

any fluid or semi-fluid of the body

labyrinth

series of intricate communicating passages. Rests inside the skull bones.

includes the cochlea, semicircular canals, and vestibule.

opaque

substance or surface that neither transmits nor allows the passage of light

perilymph

fluid that very closely resembles spinal fluid but is found in the cochlea

photopigment

light-sensitive pigment in the retinal cones and rods that absorbs light and initiates the visual process. Visual pigment.

refractive

ability to bend light rays as they pass from one medium to another

stereopsis

depth perception provided by visual information derived from two eyes located in slightly different positions so that each produces its own unique view of an object.

eye

globe-shaped organ composed of three distinct tunics (layers): the fibrous tunic, the vascular tunic, and the sensory tunic.

Fibrous tunic

outermost layer of the eyeball. Serves as a protective coat for the more sensitive structures beneath. Includes the sclera, cornea, and conjunctiva.

sclera

“white of the eye” provides strength, shape, and structure to the eye. As it passes in front of the eye, it bulges forward to become the cornea.

cornea

sclera bulges forward to become this structure. Transparent to allow light to enter the interior of the eye. Relies on eye fluids for nourishment (no capillaries).

conjunctiva

covers the outer surface of the eye and lines the eyelids.

vacular tunic (uvea)

consists of the choroid, iris, and ciliary body.

choroid

provides the blood supply for the entire eye. Contains pigmented cells that prevent extraneous light from entering the inside of the eye. An opening in this structure allows the optic nerve to enter the inside of the eyeball.

The anterior portion contains 2 modified structures: iris & ciliary body.

iris

colored, contractile membrane with a perforated center called the pupil. Regulates the amount of light passing through the pupil to the interior of the eye.

pupil

perforated center of the iris. As environmental light increases, this structure constricts; as light decreases, the pupil dilates.

ciliary body

circular muscle that produces aqueous humor. Attached to a capsular bag that holds the lens between the suspensory ligaments. As this muscle contracts and relaxes, it alters the shape of the lens making it thicker or thinner.

accommodation (Acc)

the lens’ ability to change shape to allow the eye to focus on an image. The ciliary muscle contracts and relaxes to alter the shape of the lens.

sensory tunic

innermost delicate, double-layered retina. Composed of a thin, outer pigmented layer lying over the choroid; and a thick, inner nervous layer (visual portion).

Responsible for the reception and transmission of visual impulses to the brain. 2 types of visual receptors: rods & cones

rods

function in dim light and produce black-and-white vision.

cones

function in bright light and produce color vision.

macula

highly sensitive structure in the central portion of the retina. Responsible for central (straight-ahead”) vision required for reading, driving, detail work, and recognizing faces.

fovea

composed of only cones that lie very close to each other. Provides the greatest acuity for color vision. Located in the center of the macula. When the eye focuses on an object, light rays from the object are directed here.

photopigment (visual pigment)

Chemical found in rods and cones. As light strikes this chemical, a chemical change occurs that stimulates rods and cones.

optic nerve

transmits chemical change impulses to the brain, where they are interpreted as vision.

optic disc

Location where the optic nerve and blood vessels of the eyes enter

blind spot

center of the optic disc. Contains neither rods nor cones.

aqueous humor

continuously produced by the ciliary body. Drains from the eye through a small opening (canal of Schlemm). Found in the posterior chamber and anterior chamber of the anterior portion of the eye. Nourishes the lens and cornea. One of two major fluids of the eye.

vitreous chamber

jellylike substance that fills the interior of the eye. Second major humor of the eye.

refractive structures of the eye

vitreous humor, lens, and aqueous humor. They focus light rays sharply on the retina. If one of these structures is functioning improperly, vision is impaired.

adnexa (of the eye)

include all supporting structures of the eye globe. Six extra-ocular muscles control the movement of the eye.

Superior, inferior, lateral, and medial rectus muscles; and the superior and inferior oblique muscles. These muscles coordinate the eyes in a synchronized manner.

stereopsis

binocular perception of depth or 3D space. In normal vision, each eye views an image from a somewhat different vantage point; thus transmitting a slightly different image to the brain.

conjunctiva

lines the inner surface of the eyelids and sclera. Lubricates the eye by producing mucus and tears; although a smaller volume than the tears associated with the lacrimal apparatus.

lacrimal glands

produce tears that bathe and lubricate the eyes. Lie superior and to the outer edge of each eye.

canthi (singular, canthus)

inner edges of the eyes that collect tears.

lacrimal canals

pinpoint openings where tears pass through.

nasal cavity

tears finally lead to inside lining of mucous membranes here

external ear

outer ear. Conducts sound waves through air

tympanic cavity

the middle ear. Conducts sound-waves through bone.

labyrinth

inner ear. Conducts soundwaves through fluid.

auricle (pinna)

collects waves travelling through air, then channels them to the external auditory canal (ear canal)

external auditory canaal

slender tube lined with glands that produce a waxy secretion (cerumen).

cerumen

its stickiness traps tiny foreign particles and prevents them from entering the deeper areas of the canal.

tympanic membrane (tympanum or eardrum)

flat, membranous structure drawn over the end of the ear canal. Sound-waves entering the ear canal strike against this membrane, causing it to vibrate.

ossicles

three smallest bones of the body. Vibrations from the tympanic membrane cause these bones to move. Locate. Malleus (hammer), incus (anvil), and the stapes (stirrups). Located within the tympanic cavity and form a connection between the tympanic membrane and cochlea.

cochlea

snail-shaped structure filled with fluid (perilymph). First structure of the inner ear.

organ of Corti

highly sensitive hearing structure that lines the inner surface of the cochlea. Contains tiny nerve endings hair cells.

oval window

membrane-covered opening on the external surface of the cochlea. Provides a place for attachment of the stapes. Movement of the ossicles causes the stapes to exert a gentle pumping action against this structure. This action forces the perilymph to disturb the hair cells, generating impulses that are transmitted to the brain by the auditory nerve; interpreted as sound.

eustachian tube

connects the middle ear to the pharynx. It equalizes pressure on the outer and inner surfaces of the eardrum. When there is a pressure inequality, a deliberate swallow will commonly restore equality.

vestibular system

joins the cochlea and semicircular canals. Contains the semicircular canals and vestibule. Devoted to control of equilibrium (balance) and eye movements.

ambly/o

dull, dim

-opia

vision

aque/o

water

-ous

pertaining to

blephar/o

eyelid

-ptosis

prolapse, downward displacement

choroid/o

choroid

conjunctiv/o

conjunctiva

-al

pertaining to

core/o

pupil

pupill/o

pupil

-graphy

process of recording

corne/o

cornea

cycl/o

ciliary body of the eye; circular; cycle

dacry/o

tear; lacrimal apparatus (duct, sac, or gland)

lacrim/o

tear; lacrimal apparatus (duct, sac, or gland)

dacryocyst/o

lacrimal sac

glauc/o

gray

gont/o

angle

irid/o

iris

kerat/o

horny tissue; hard; cornea

ocul/o

eye

myc/o

fungus

-osis

abnormal condition; increase (used primarily with blood cells)

opthalm/o

eye

opt/o

eye, vision

-metry

act of measuring

optic/o

eye, vision

phac/o

lens

phot/o

light

presby/o

old age

retin/o

retina

scler/o

hardening; sclera (white of eye)

scot/o

darkness

vitr/o

vitreous body (of the eye)

audi/o

hearingl

labyrinth/o

labyrinth (inner ear)

mastoid/o

mastoid process

ot/o

ear

-rrhea

discharge, flow

salping/o

tubes (usually fallopian or eustachian [auditory] tubes)

staped/o

stapes

tympan/o

tympanic membrane (eardrum)

myring/o

tympanic membrane (eardrum)

-acusia

hearing

-cusis

hearing

presby-

old age