Ear Structure & Function - PowerPoint Presentation

Slide1

Ear Structure & Function

12-13

January 2014Slide2

External Ear

Structures:

Pinnaauditory canalear drumFunction: Funnel and conduct sound to middle ear

Anatomy of the EarSlide3

Middle Ear

Structures:

OssiclesMalleusIncusStapes

Eustacian / auditory tube

Function:

Amplify and conduct sound to inner ear

Anatomy of the EarSlide4

Inner Ear

Structures:

Osseous labyrinthSemicircular canalsVestibulecochlea

Function: Receive sound and equilibrium stimuli

Anatomy of the EarSlide5

NOTE:

Diagrams are misleading.

The entire inner is bony, except for the labyrinth which is a series of cavities (spaces) within the bone. Anatomy of the EarSlide6

Outer (External) Ear

Function

:Slide7

Outer (External) Ear

Function

: to funnel and conduct sound to the middle earPinna collect sound waves and direct to the tympanic membranes … but in humans, not very effectively.Cerumen

(ear wax) lines the external auditory canal.AntibacterialAlso 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

A reflex tightens the ear drum in response to loud, low-pitched sounds – this reduces the sound transmitted to the ear and

protectes

our hearingSlide8

Disorders of the Outer Ear

Ear Wax Blockage

Ear wax can become impacted, usually from hearing aid use or inappropriate methods of cleaning the earsCan cause temporary loss of hearing Slide9

Disorders of the Outer Ear

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.

Picture through an

otoscope

. Notice that the canal is red but the ear drum is clear and not bulging.Slide10

Function

:

Middle EarSlide11

Function

: to AMPLIFY the sound and conduct it to the oval window of the inner ear.

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

m

embrane-covered opening to the

inner ear.

Middle EarSlide12

Structure

Tube that connects the middle ear to the nose and throat

Mostly closed, but opens when we move our jawWhy do we have it?Equalize pressure in the middle ear Drain fluids to the throat

Eustachian Tubes

Remember: the tympanic membrane seals the middle ear from the outer ear – so the only way for air / fluids to leave the middle ear is through the

eustachian

tubes

This is why its helpful to yawn or chew gum on a plane rideSlide13

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 infectionBabies 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

Disorders of the Middle EarSlide14

myringotomy

–

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.

Disorders of the Middle EarSlide15

Hearing takes place within the cochlea of the inner ear.

Cochlea is a long, curled cavity with three layers

2 layers of perilymph – a plasma-like fluidIn-between: a system of membranes that contain the organ of

Corti and the

mechanoreceptors (hair cells)

that create the nerve impulse

Hearing & the Inner EarSlide16

Hearing & the Inner Ear

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?Slide17

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 impulseHearing & the Inner Ear

Different frequencies (pitch) vibrate the membrane in different locations.

High pitches are heard that the front, low at the back.Slide18

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 impulseHearing & the Inner Ear

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

Watch me!

Just for fun!Slide19

What were our objectives, and what did you learn about

them?

What was our learner profile trait and how did we exemplify it?How does what we did today address our unit question?Closure