Anatomy and Anatomy and Physiology of the EarPhysiology of the Ear

3 Parts of the EarOuter, Middle, and Inner Ear

• Part 1 OUTER EAR- Pinna to Tympanic Membrane

The “pre amp” –makes sound waves stronger

Does Ear Wax Have a Purpose?

2 important functions

1.Keeps skin in ear canal

soft

2. Keeps bugs out (they don’t like the taste)

What Causes Outer Ear Hearing Loss ?

• Wax pushed up against eardrum (tympanic membrane)

from q-tip use • Sharp objects that puncture tympanic

membrane• Born with damaged ear canal or

without pinna• Swimmer’s Ear - what is that?

Swimmer’s EarSwimmer’s Ear

• Water +Water +

• Germs or bacteria +Germs or bacteria +

• Wax in the auditory canal = mold Wax in the auditory canal = mold

• ComplicationsComplications

• How to treat it????How to treat it????

Tympanic MembraneHealthy TM is translucent is

silvery in color

Red or pink or bulging shows an infection.

TYMPANIC MEMBRANCENormal versus Infection

Part 2 - Middle Ear

• Sound waves change to mechanical energy in the middle ear

• ½” chamber

What are the parts of the Middle Ear?

• Back of tympanic membrane

• 3 small bones

• Eustachian tube

Malleus, Incus, and Stapes3 smallest bones in the body

Eustachian Tube

• What is the purpose?

• Drain cells/tissue • Equalize air

pressure

What Causes Hearing Loss in the Middle Ear ?

• Calcium deposits on bones

Solution ?

• Loud sudden noises- firecracker, gunshot

Solution?

• Trauma to the head- fall, car accident

• Otitis media- what is that???

Otitis Media• Most common ailment

for children- Why???

• Germs travel up eustachian tube-lodge in middle ear

Why are Parents concerned?

• Ossicles do not vibrate correctly = 25dB hearing loss

• Critical time for learning langauge

• Treatments??

Antibiotics

• Children over medicated?

• Will condition improve by itself?

• Are new strains of bacteria developing?

• Risks for developing speech?

Ear Tubes- Chronic Otitis MediaSmall slit made in TM and tube put

in for drainage from Middle Ear- most tubes fall out after a few

months

Which is your “real voice”?

• The voice YOU hear?

• Sorry- you’re the only one who hears it

• Why?

• The voice on a tape?

• This is your voice to the world

                     

CONDUCTIVE HEARING LOSS

• Any hearing loss occurring in the OUTER or MIDDLE EAR• Examples ?????• Malformed pinna, too much wax, swimmers ear (or water stuck in ear),torn tympamic membrane, Otitis media,

calcium deposits on ossicles, torn muscles that control the ossicles

Conductive Hearing Loss can be repaired

The Inner Ear

• Cochlea• semi- circular canals • auditory nerve (8th

cranial nerve)

• Note the changes of energy as the sound waves come through each part of the ear

Entrance to the Inner ear

The 3 bones vibrate causing a disturbance at the “Oval Window”

Parts of the Inner Ear

• Cochlea

• Semi-circular Canals

• Auditory (8th cranial) nerve

Why do you get dizzy?

• Liquid in Semi –Circular canals

• Information from cilia sent to brain

• Must match info sent from eyes

• Dizzy = brain doesn’t know what to follow

The COCHLEA

• Size of a pea• Fluid –filled• Contains up to 20,000

cilia or hair-like nerve endings

• Movement of the fluid stimulates the cilia

• Creates Electrical impulses

Auditory nerve- carries electrical impulses from cilia (in cochlea and semicircular canals) to the brain for

interpretation

Sensorineural Hearing Loss(Hearing loss in the Inner Ear)

Known etiologies-• Multiple Sclerosis• Leukemia • Sickle cell• syphilis• Bacterial infection( meningitis)• Mumps• ototoxic drugs (aspirin)• tumor (from cell phones?)• noise explosion• menieres disease• genetic connexin 26• toys- noise levels• membrane rupture• airbag (ruptures tympanic membrane, tinnitus hearing loss)• Premature birth• unknown

Review--Pathway of Sound• Sound waves enter pinna travel through auditory canal• Sound waves strike tympanic membrane causing vibrations

(mechanical energy)• Vibrating TM causes ossicles to vibrate• Vibrating stapes bone at oval window generates movement of

cochlear fluid (Hydralics)• Fluid movement stimulates cilia- lined cochlea• Cilia sends electrical impulses along auditory nerve to brain

for interpretation