Basic Anatomy of Ear

how long is the External Auditory Meatus/canal in adults?

1 inch in length

Ossicle chain is formed by

3 small bones; the malleus, incus and stapes.

Tympanic Membrane or Eardrum

A thin concave-shaped structure that is highly elastic that vibrates in response to sound waves that travel down the canal

Oval window

A thin membrane that marks the entrance to the inner ear

Other functions of the Pinna:

Serves as a natural resonator and Assists with localization

Ossicle Chain

Spans the length of the middle ear cavity, much like a suspension bridge

Vestibular system

Structures of the inner ear responsible for supplying information to the brain regarding balance and spatial orientation.

Pinna

The funnel-shaped outermost part of the ear that serves to collect sound waves and channel them into the ear canal

Organ of Corti

The intricate structure that runs along the center of the membranous labyrinth of the cochlea and contains the auditory sensory receptor cells.

Cochlea

The portion of the inner ear that contains the sensory cells of the auditory system; Is a coiled structure that spirals 2.5 times around a central core of bone

Localization

The process of determining where sound originates in space

The Middle Ear

The section of the ear containing the ossicles, is connected to the outer ear by the tympanic membrane (eardrum) and is bound medially by the cochlea.

Stapedius Muscle

The small muscle that attaches to the stapes and contracts in response to high-intensity sound

Nasopharynx

The space located behind the nose and above the roof of the mouth

A healthy eardrum is described as this color

pearl-grey

stereocilla

small hairlike projections located on the top of each haircell (of the basilar membrane)

Attached to the neck of the stapes is the tendon of the

stapedius muscle

The third & smallest of the ossicles (smallest bone in the body)

stapes

Middle ear space or Tympanic cavity

the air-filled cavity housed within the temporal bone of the skull; is roughly cube-shaped; is lined with mucous membrane; is located behind the tympanic membrane,

two major components of the interior section of the ear

the cochlea and vestibular system.

Malleus

the largest of the ossicles; is fastened to the eardrum; articulates with the incus, the next bone in the chain

Incus

the middle bone of the ossicular chain; it articulates with the malleus at the top; it has a projection that is joined to the stapes at the bottom

Deficits in the vestibular system often result in problems related to

vertigo (the sensation of spinning), dizziness, and imbalance.

Central Auditory System

•The Auditory Brainstem •The Auditory Cortex of the Brain

Peripheral Auditory System

•The Outer Ear •The Middle Ear •The Inner Ear •The Vesibulocochlear Nerve

Inner Ear

It supplies information to the brain regarding balance, special orientation, and hearing.

Various ridges and depressions serve to enhance sound naturally in this part of the outer ear

Pinna

The Outer Ear

Is comprised of the pinna, or auricle and the external auditory meatus/canal.

Basilar membrane

Is non-uniform in width, stiffness, and thickness; Contains thousands of hair cells, the receptor cells for the auditory system

Stapes

Resembles a stirrup; Contains two curved arms that terminate in a flat, bony disk called the footplate; The footplate rests against the oval window

is tonotopically organized allowing it to respond differently to different frequencies of sound

Basilar membrane

Is responsible for providing auditory input to the central auditory system

Cochlea

Most of it's surface area is composed of three distinct layers of tissue:

Eardrum

Opens periodically, providing a passageway for air to ventilate the middle ear space and equalize air pressure on each side of the eardrum.

Eustachian tube

Because it is a tube, it functions as a resonator, naturally amplifying sound in the 2,700 Hz to 3,400 Hz region.

External Auditory Meatus/canal

has a slight S-shaped contour and narrows slightly as it progresses toward the eardrum

External Auditory Meatus/canal

Eustachian tube

The tube that connects the middle ear cavity with the nasopharynx; Is normally closed

External Auditory Meatus/canal

The tubular structure that extends from the concha (of the pinna) to the tympanic membrane or eardrum.

The outer region of the External Auditory Meatus/canal is marked by

a proliferation of fine hair follicles and glands that produce a substance called cerumen or earwax.

The floor of the organ of Corti is formed by the

basilar membrane.

The outer labyrinth of the cochlea is composed of

bone and is filled with a fluid called perilymph

auditory nerve fibers

collectively form the acoustic branch of the vestibulocochlear or 8th nerve; innervating (stimulating w/ nervous energy) the hair cells are auditory nerve fibers

Central Auditory System deficits include;

difficulties processing sound

The Pinna is Composed of:

flexible cartilage covered with skin

The hair cells (of the basilar membrane) are separated into two groups:

inner and outer

The outer layer of the eardrum's tissue

is a continuation of skin that lines the external canal

The middle layer of the eardrum's tissue

is a layer of fibrous tissue that provides strength and accounts for the eardrum's elastic properties.

The inner layer of the eardrum's tissue

is continuous with the mucous membrane that lines the cavity directly behind the eardrum

Peripheral Auditory System Deficits include;

loss of sensitivity

The inner labyrinth of the cochlea is composed of

membrane and contains a fluid called endolymph