Anatomy and Physiology of the Ear

3 Parts of the Ear Outer, Middle, and Inner Ear Part 1 OUTER EAR- Pinna to Tympanic Membrane The “pre amp” –makes sound waves stronger Pinna for humans has a poor design (too flat on head) try “cupping” ears and see how sound quality improves Speed of sound-Speed of sound- at 68 degrees 1,125 feet per second = 756 mph Higher temps= faster speed for sound

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 Ear Water + Germs or bacteria + Wax in the auditory canal = mold  Complications How to treat it????

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

TYMPANIC MEMBRANCE Normal 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 Stapes 3 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 Media Small 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 Wave to mechcanical to hydralic to electrical

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 Have students spin

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 Sensorineral- of the inner ear

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