Ear Structure and Function Guided Notes Name:_________________________

Ear Anatomy

Overview

Middle Ear

Structures:

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Function:

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Inner Ear

Structures:

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Function:

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External Ear

Structures:

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Function:

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NOTE: Diagrams are misleading.

The entire inner is bony, except for the labyrinth which is a series of cavities (spaces) within the bone.

Outer Ear

Function: __________________________________________________________

· Pinna collect sound waves and direct to the tympanic membranes … but in humans, not very effectively.

· Cerumen (ear wax) lines the external auditory canal.

· Antibacterial

· Also discourages bugs, mold, etc.

· Lubricates ears

· Helps trap / remove foreign particles

· The tympanic membrane (ear drum) vibrates when sound waves hit it,

transmitting the sound to the middle ear

Disorders of the outer ear

Ear Wax Blockage

· Ear wax can become impacted, usually from hear aid use or inappropriate methods of cleaning the ears

· Can cause temporary loss of hearing

Otitis Externa (Swimmer’s Ear)

· Infection of external auditory ear canal, usually due to excess moisture in the ear canal (such as from swimming), though cuts and scrapes to the ear canal can also become infected.

Middle Ear

Function: _____________________________________________________________________________

How? The tympanic membrane transmits sound to the three ossicles. The ossicles act like levers, amplifying the sound and transmitting it to the oval window, a membrane-covered opening to the inner ear.

Eustachian tubes

Structure

· Tube that connects the middle ear to the nose and throat

· Mostly closed, but opens when we move our jaw

Why do we have it?

· Equalize pressure in the middle ear

· Drain fluids to the throat

Disorders of the middle ear

Otitis media (middle ear inflammation / infection) –

· Inflammation (often with the buildup of infected fluids) within the middle ear

· Visible with an otoscope as a bulging eardrum

· Usually caused from a respiratory infection

· Babies who are allowed to drink bottles while lying down are also very likely to get ear infections

· Much more common in young children, because their Eustachian tubes are narrower and more horizontal

· Ear tubes are often recommended for children who experience chronic middle ear infections or fluid build-up

· The tube is placed in the ear drum, but performs the functions of a eustachian tube – ventilating and draining the middle ear.

Hearing and the inner ear

Hearing takes place within the cochlea of the inner ear.

· Cochlea is a long, curled cavity with three layers

· 2 layers of _______________ – a plasma-like fluid

· In-between: a system of membranes that contain the ______________________ and the ______________________ _______________________ that create the nerve impulse

The top diagram is a cross-section of the cochlear cavity.

Take a moment to figure out …

· What fills the scala vestibuli?

· The scala tympani?

· The cochlear duct?

· When the stapes beats against the oval window, it causes pressure waves within the perilymph

· The movement of the perilymph disturbs the cilia (receptors) of the Organ of Corti, generating a nerve impulse

· Different frequencies (pitch) vibrate the membrane in different locations. High pitches are heard that the front, low at the back.

· The round window is a membrane-covered opening just below the oval window. It bulges to keep the pressure waves from bouncing back.