A. ANATOMY OF EARThe ear is the organ of hearing. The parts of the ear include:

external or outer ear, consisting of:

a. pinna or auricle - the outside part of the ear. Convuluted funnel of cartilage that is attached to the side of the headf. Function: help to collect sound vibration near the opening of the ear; direct (rather poorly) sound waves into the external auditory canal.

b. external auditory canal or tube - the tube that connects the outer ear to the inside or middle ear. Function: sound waves are funneled down the canal and are amplified; natural acidity helps to protect against infections; secrets cerumen (ear wax) to protect canal from drying out also helps repel insects.

tympanic membrane - also called the eardrum. A thin, tough, flexible, fibrous membrane, approximately 1/3 inch in a diameter attached to the external auditory canal. Grey color and cone shaped resting on 90-degree angle into midlle ear cavity. The tympanic membrane divides the external ear from the middle ear. Function: sound waves from the external auditory canal hit this membrane and cause it to vibrate; reproduce frequency and form of sound wave.

middle ear (tympanic cavity), consisting of:

a. ossicles - three small bones that are connected and transmit the sound waves to the inner ear. Form the mechanical linkages between the tympanic membrane and the inner ear; deliver sound vibrations to inner ear fluids; amplify airbone sound by approximately 30dB. The bones are called:

malleus; a small bone (hammer or club-shaped), its handle attaches to the tympanic membrane at a place called the umbo. Its other end has a round head.

Incus; a small bone (anvil shaped) in which the maleus rests and then connects to the stapes.

Stapes; a small bone (striruup shaped which is a connected to the incus, and with its oval footplate connect to the oval window of the inner ear.

b. eustachian tube - a canal that links the middle ear with the throat area. The eustachian tube helps to equalize the pressure between the outer ear and the middle ear. Having the same pressure allows for the proper transfer of sound waves. The eustachian tube is lined with mucous, just like the inside of the nose and throat.

Function: equalizes air pressure inside and outside the tympanic membrane and allows the drainage of normal and diseased middle ear secretions

inner ear, consisting of:

a. cochlea (contains the nerves for hearing). A bony, spiral-shaped cavity coiled 2 ½ times (like a snail shell); filled with fluid and divided into three sections; pea sized; houses organ corti. Function is converts stimulus from outside environment into nerve impulse for transmission to the brain.

b. vestibule (contains receptors for balance)c. semicircular canals (contain receptors for balance); embedded in temporal bone,

three seoarate loops, contaoin cleasr, watery liquid. Function is hair cells within canals perceive sense of balance and position in space; fluid flow in certain directions when you move your head; different movements affect different canals aids in maintaining balance and has nothing to do with hearing.

B. PHYSIOLOGY OF EAR