HA 15 & 16

As the stapes vibrates

(at the oval window) the sound waves are passed to the fluid in the inner ear. The movement of this fluid stimulates the hair cells of the spiral organ of Corti and initiates the nerve impulses that travel to the brain by way of the acoustic nerve.

The tympanic membrane

(eardrum) has a translucent, pearly gray appearance and serves as a partition stretched across the inner end of the auditory canal, separating it from the middle ear.

labyrinth

(inner ear)is fluid filled and is made up of the bony labyrinth and an inner membranous labyrinth.

tympanic cavity

(middle ear)is a small, air-filled chamber in the temporal bone. It is separated from the external ear by the eardrum and from the inner ear by a bony partition containing two openings, the round and oval windows.

sensorineural hearing

(perceptive) transmission of sound waves in the inner ear is referred to as

bone conduction

(though less efficient) serves to augment the usual pathway of sound waves through air, bone, and finally fluid

Eyelids

(upper and lower) are two movable structures composed of skin and two types of muscle: striated and smooth. (purpose is to protect the eye from foreign bodies and limit the amount of light entering the eye)

physiologic cup

A smaller circular area that appears slightly depressed is referred to as the (one-third the size of the entire optic disc)

eustachian tube

Air pressure is equalized on both sides of the tympanic membrane by means of the (which connects the middle ear to the nasopharynx)

optic chiasma

At the point where the optic nerves from each eyeball cross-the nerve fibers from the nasal quadrant of each retina (from both temporal visual fields) cross over to the opposite side.

Cerumen

Modified sweat glands in the external ear canal secrete (a wax-like substance that keeps the tympanic membrane soft)

The external auditory canal

S-shaped in the adult.

Pupil

The central aperture of the iris is called the.

Muscles in the iris

adjust to control the pupil's size, which controls the amount of light entering the eye.

A retinal depression

aka fovea centralis is located adjacent to the optic disc in the temporal section of the fundus. (surrounded by the macula)

The muscle fibers of the iris

also decrease the size of the pupil to accommodate for near vision and dilate the pupil when far vision is needed.

Vessels

are dark red and grow progressively narrower as they extend out to the peripheral areas.

The fovea centralis and macular area

are highly concentrated with cones and form the area of highest visual resolution and color vision.

The rods

are highly sensitive to light, regulate black and white vision, and function in dim light.

Eyelashes

are projections of stiff hair curving outward along the margins of the eyelids that filter dust and dirt from air entering the eye.

The cornea and lens

are the main eye components that refract (bend) light rays on the retina. The image projected on the retina is upside down and reversed right to left from the actual image.

Sound waves

are then transmitted through auditory ossicles as the vibration of the eardrum causes the malleus, the incus, and then the stapes to vibrate.

Suspensory ligaments

attached to the ciliary body support the position of the lens. The lens functions to refract (bend) light rays onto the retina. Adjustments must be made in refraction depending on the distance of the object being viewed. Refractive ability of the lens can be changed by a change in shape of the lens (which is controlled by the ciliary body). The lens bulges to focus on close objects and flattens to focus on far objects.

The middle layer contains

both an anterior portion, which includes the iris and the ciliary body, and a posterior layer, which includes the choroid.

Both the external ear and the tympanic membrane

can be assessed by direct inspection and by using an otoscope. (middle and inner ear cannot be directly inspected)

The retinal vessels

can be readily viewed with the aid of an ophthalmoscope.

Arterioles

carry oxygenated blood and appear brighter red and narrower than the veins.

The pupillary light reflex

causes pupils immediately to constrict when exposed to bright light.

The bony labyrinth has three parts

cochlea, vestibule, semicircular canals.

lacrimal apparatus

consists of glands and ducts that serve to lubricate the eye.

ciliary body

consists of muscle tissue that controls the thickness of the lens, which must be adapted to focus on objects near and far away.

external layer

consists of the sclera and cornea.

The inner cochlear duct

contains the spiral organ of Corti, which is the sensory organ for hearing.

The chorioid layer

contains the vascularity necessary to provide nourishment to the inner aspect of the eye and prevents light from reflecting internally. Anteriorly, it is continuous with the ciliary body and the iris.

The outer part of the canal

curves up and back and the inner part of the canal curves down and forward.

The innermost layer, the retina

extends only to the ciliary body anteriorly. It receives visual stimuli and sends it to the brain.

The aqueous humor

filters out of the eye from the posterior to the anterior chamber then into the canal of Schlemm through a filtering site called the trabecular meshwork.

The cones

function in bright light and are sensitive to color.

Cerumen

has bacteriostatic properties, and its sticky consistency serves as a defense against foreign bodies.

Aqueous humor

helps to cleanse and nourish the cornea and lens as well as maintain intraocular pressure.

direct reflex

in which constriction occurs in the eye exposed to the light (oculomotor nerve)

indirect or consensual reflex

in which exposure to light in one eye results in constriction of the pupil in the opposite eye (oculomotor nerve)

The lens

is a biconvex, transparent, avascular, encapsulated structure located immediately posterior to the iris.

Iris

is a circular disc of muscle containing pigments that determine eye color.

The optic disc

is a cream-colored, circular area located on the retina toward the medial or nasal side of the eye. It is where the optic nerve enters the eyeball. The optic disc can be seen with the use of an ophthalmoscope and is normally round or oval in shape, with distinct margins.

The sclera

is a dense, protective, white covering that physically supports the internal structures of the eye. It is continuous anteriorly with the transparent cornea (the "window of the eye").

Accommodation

is a functional reflex allowing the eyes to focus on near objects by ciliary muscles causing an increase in the curvature of the lens.

Conjunctiva

is a thin, transparent, continuous membrane that is divided into two portions: a palpebral and a bulbar portion.

white space between open eyelids

is called the palpebral fissure.

The external ear

is composed of the auricle or pinna and the external auditory canal.

The eyeball

is composed of three separate coats or layers

The membrane of tympanic

is concave and located at the end of the auditory canal in a tilted position such that the top of the membrane is closer to the auditory meatus than the bottom.

upper eyelid

is larger, more mobile, and contains tarsal plates made up of connective tissue. (meibomian glands, which secrete an oily substance that lubricates the eyelid)

anterior chamber

is located between the cornea and iris (chambers are filled w/aqueous humor, a clear liquid substance produced by the ciliary body)

the vitreous chamber

is located in the area behind the lens to the retina. It is the largest of the chambers and is filled with a vitreous humor that's clear and gelatinous.

Eyeball

is located in the eye orbit, a round, bony hollow formed by several different bones of the skull.

posterior chamber

is the area between the iris and the lens. (chambers are filled w/aqueous humor, a clear liquid substance produced by the ciliary body)

The ear

is the sense organ of hearing and equilibrium.

orbit of the eye

it is surrounded by a cushion of fat. The bony orbit and fat cushion protect the eyeball.

In the eye

light must pass through transparent media (cornea, aqueous humor, lens, and vitreous body) before reaching the retina.

palpebral conjunctiva

lines the inside of the eyelids, and the bulbar conjunctiva covers most of the anterior eye, merging with the cornea at the limbus. The point at which the palpebral and bulbar conjunctivae meet creates a folded recess that allows movement of the eyeball. This transparent membrane allows for inspection of underlying tissue and serves to protect the eye from foreign bodies.

The lacrimal gland

located in the upper outer corner of the orbital cavity just above the eye, produces tears.

Sensory receptors

located in the vestibule and in the membranous semicircular canals, sense position and head movements to help maintain both static and dynamic equilibrium. vestibular nerve Nerve fibers from these areas form the (which connects with the cochlear nerve to form the eighth cranial nerve (acoustic or vestibulocochlear nerve).

Visual perception

occurs as light rays strike the retina, where they are transformed into nerve impulses, conducted to the brain through the optic nerve, and interpreted.

The retina consists

of numerous layers of nerve cells, including the cells commonly called rods and cones. (photoreceptors)

The cornea

permits the entrance of light, which passes through the lens to the retina. It is well supplied with nerve endings, making it responsive to pain and touch.

limbus

point where the sclera meets the cornea.

A visual field

refers to what a person sees with one eye. The visual field of each eye can be divided into four quadrants: upper temporal, lower temporal, upper nasal, and lower nasal

The tympanic membrane

separates the external ear from the middle ear.

The eyeball contains

several chambers that serve to maintain structure, protect against injury, and transmit light rays.

extraocular muscles

six muscles attached to the outer surface of each eyeball

wisp of cotton

stimulates a blink in both eyes known as the corneal reflex CN: trigeminal

As the lid blinks

tears wash across the eye then drain into the puncta, which are visible on the upper and lower lids at the inner canthus.

Ear consists of three distinct parts

the external ear, the middle ear, and the inner ear.

Tears empty into

the lacrimal canals and are then channeled into the nasolacrimal sac through the nasolacrimal duct. They drain into the nasal meatus.

eyelids join at two points

the lateral (outer) canthus and medial (inner) canthus. The medial canthus contains the puncta, two small openings that allow drainage of tears into the lacrimal system, and the caruncle, a small, fleshy mass that contains sebaceous glands.

These muscles control six different directions of eye movement. Four rectus muscles are resp. for straight movement, two oblique muscles are resp. for diagonal movement. Each muscle coordinates with a muscle in the opposite eye. (parallel movement) Innervation -three cranial nerves

the oculomotor (III) trochlear (IV), and abducens (VI).

The middle ear contains

three auditory ossicles: the malleus, the incus, and the stapes. These tiny bones are responsible for transmitting sound waves from the eardrum to the inner ear through the oval window.

conductive hearing

transmission of sound waves through the external and middle ear is referred to as

eye

transmits visual stimuli to the brain for interpretation and, in doing so, functions as the organ of vision.

Four sets of arterioles and venules

travel through the optic disc, bifurcate, and extend to the periphery of the fundus.

Sound vibrations

traveling through air are collected by and funneled through the external ear and cause the eardrum to vibrate.

conductive hearing loss

would be related to a dysfunction of the external or middle ear (e.g., impacted ear wax, otitis media, foreign object, perforated eardrum, drainage in the middle ear, or otosclerosis).

sensorineural loss

would be related to dysfunction of the inner ear (i.e., organ of Corti, cranial nerve VIII, or temporal lobe of brain).