Anatomy and Physiology of the Ear

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Anatomy and Physiology of the Ear
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3 Parts of the EarOuter, Middle, and Inner Ear

• Part 1 OUTER EAR- Pinna to Tympanic Membrane
• The pre amp makes sound waves stronger

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Does Ear Wax Have a Purpose?

• 2 important functions
• 1.Keeps skin in ear canal
• soft
• 2. Keeps bugs out ?
• (they dont like the taste)

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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
• Swimmers Ear - what is that?

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Swimmers Ear

• Water
• Germs or bacteria
• Wax in the auditory canal mold ?
• Complications
• How to treat it????

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Tympanic Membrane

• Healthy TM is translucent is silvery in color
• Red or pink or bulging shows an infection.

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TYMPANIC MEMBRANCENormal versus Infection
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Part 2 - Middle Ear

• Sound waves change to mechanical energy in the
  middle ear
• ½ chamber

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What are the parts of the Middle Ear?

• Back of tympanic membrane
• 3 small bones
• Eustachian tube

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Malleus, Incus, and Stapes3 smallest bones in
the body
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Eustachian Tube

• What is the purpose?
• Drain cells/tissue
• Equalize air pressure

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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???

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Otitis Media

• Most common ailment for children- Why???
• Germs travel up eustachian tube-lodge in middle
  ear

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Why are Parents concerned?

• Ossicles do not vibrate correctly 25dB hearing
  loss
• Critical time for learning langauge
• Treatments??

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Antibiotics

• Children over medicated?
• Will condition improve by itself?
• Are new strains of bacteria developing?
• Risks for developing speech?

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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
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Which is your real voice?

• The voice YOU hear?
• Sorry- youre the only one who hears it
• Why?

• The voice on a tape?
• This is your voice to the world ?

                     
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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

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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

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Entrance to the Inner ear
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The 3 bones vibrate causing a disturbance at the
Oval Window
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Parts of the Inner Ear

• Cochlea
• Semi-circular Canals
• Auditory (8th cranial) nerve

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Why do you get dizzy?

• Liquid in Semi Circular canals
• Information from cilia sent to brain
• Must match info sent from eyes
• Dizzy brain doesnt know what to follow

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The COCHLEA

• Size of a pea
• Fluid filled
• Contains up to 20,000 cilia or hair-like nerve
  endings

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• Movement of the fluid stimulates the cilia
• Creates Electrical impulses

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

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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