Download The Ear

The Nervous System
The Five Senses-The Ear
The Ear
• The ear is made up of three divisions:
 Outer Ear
-Pinna (Auricles)
-External Auditory Canal
 Middle Ear
-Tympanic Membrane (ear drum)
-Auditory Ossicles (bones-malleus (hammer),
incus(anvil), stapes(stirrup))
-Middle Ear Cavity
-Eustachian Tube
 Inner Ear
-Oval Window
-Round Window
-Cochlea
-Semicircular Canals (Vestibular Apparatus)
Parts of the Ear: Outer Ear

Pinna: helps to collect sound
vibrations near the openings of the ear;
directs sound waves into the external
auditory canal

External Auditory Canal: sound
waves are funneled down the canal and
are amplified; natural acidity helps to
protect agains infections; secretes
ceremun(ear wax) to protect canal from
drying out and to repel insects.
Parts of the Ear: Middle Ear
 Tympanic Membrane (ear drum): sound waves
from the external auditory canal hit this membrane
and cause it to vibrate; reproduces frequency and
form of sound wave
 Auditory Ossicles: malleus (hammer), incus
(anvil), and stapes (stirrup) form the mechanical
linkages between the tympanic membrane and the
inner ear; deliver sound vibrations to inner ear
fluids ; amplify airborne sound by approximately 30
decibels
 Middle Ear Cavity: equalizes air pressure inside
and outside the tympanic membrane and allows the
drainage of normal and diseased middle ear
secretions
 Eustachian Tube: equalizes air pressure inside
and outside the tympanic membrane and allows the
drainage of normal and diseased middle ear
secretions
Parts of the Ear: Inner Ear
 Oval Window: vibrations from the ossicles are
transferred to the cochlea via the action of the stapedial
footplate in the oval window (footplate of the stapesfits
withing the oval window, moves in and out with a
pumping action; ossicles form a chain extending from
tympanic membrane to oval window
 Round Window: aids fluid motion within the cochlea
and serves to equalize the hydraulic pressure
 Cochlea: converts stimulus from outside environment
(sound) into nerve impulses for transmission to the brain
 Semicircular Canals (vestibular apparatus): hair cells
within canals perceive sense of balance and position in
space; fluid flows in certain directions when you move
your head; different movements affect different canals;
aids in maintaining balance and has nothing to do with
hearing
Parts of the Ear
• Click here to view a tutorial of the
structures and functions of the parts of the
ear.
How the Ear Works
1. Sound waves enter your ear, travel
through the auditory canal, and set up
vibrations in the eardrum.
2. The vibrations of the eardrum cause the
bones in the middle ear to move back and
forth like tiny levers. This lever action
converts the large motions of the eardrum
into shorter, more forceful motion of the
stapes.
How the Ear Works
3. The footplate at the inner end of the
stapes moves in and out of the oval
window at the same rate that the eardrum
is vibrating.
4. The movement of the footplate sets up
motions in the fluid that fills the cochlea.
5. The movement of the fluid causes the
hairs immersed in the fluid to move. The
movement stimulates the attached cell to
send a tiny impulse along the fibers of the
auditory nerve to the brain.
How the Ear Works
6. In the brain the impulse is translated into
the sensation you know as sound.
Parts of the Ear
Pinna
Auditory Ossicles