1. ANATOMY AND PHYSIOLOGY OF THE EAR (HEARING)

2. Main Components of the Hearing Mechanism:
Outer Ear
Middle Ear
Inner Ear
Central Auditory Nervous System

3. Structures of the Outer Ear
Auricle (Pinna)
Collects sound

4. External Auditory Canal:
Approx. 1 inch in length
“S” shaped
Lined with cerumen glands
Outer 1/3 surrounded by cartilage
Inner 2/3’s surrounded by mastoid bone

5. Tympanic Membrane: Thin membrane
Forms boundary between outer and middle ear
Vibrates in response to sound

6. The Ossicles: A: Malleus B: Incus C: Stapes Stapedius Muscle
Smallest bones in the body
Acts as a lever system
Footplate of stapes enters oval window of the cochlea
Stapedius Muscle
Connects stapes to wall of middle ear
Contracts in response to loud sounds (called the Acoustic Reflex)

7. Eustachian Tube (AKA: “The Equalizer”)
Lined with mucous membrane
Connects middle ear to nasopharynx
“Equalizes” air pressure

8. Structures of the Inner Ear

9. Cochlea &Organ Of Corti
Snail shaped organ with a series of fluid-filled tunnels
Converts mechanical energy to electrical energy
Organ Of Corti
The end organ of hearing
Contains stereocilia and
hair cells.

10. Central Auditory System
VIIIth Cranial nerve or “Auditory Nerve”
Carries signals from cochlea to brain
Auditory Cortex
Temporal lobe of the brain where sound is perceived and analyzed

11. How Sound Travels Through The Ear...
1. Acoustic energy, in the form of sound waves, is channeled into the ear canal by the pinna
2. Sound waves hit the tympanic membrane and cause it to vibrate, like a drum, changing it into mechanical energy
3. The malleus, which is attached to the tympanic membrane, starts the ossicles into motion
4. The stapes moves in and out of the oval window of the cochlea creating a fluid motion
5. The fluid movement causes membranes in the Organ of Corti to shear against the hair cells
6. This creates an electrical signal which is sent up the Auditory Nerve to the brain
The brain interprets it as sound!

12. Vestibular System Consists of three semi-circular canals
Shares fluid with the cochlea
Controls balance