How
do we hear?
The
ear consists of three major parts:
- the
outer ear
- the
middle ear
- the
inner ear.
The
outer ear includes the pinna (the visible part of the ear) and
the ear canal. The tympanic membrane (eardrum) separates the outer
ear from the middle ear.
The
middle ear is an air-filled space that contains 3 tiny bones
-
the malleus, incus and stapes, which transmit sound from
the middle ear to the inner ear. The middle ear is connected to
the back of the nose and upper throat by the Eustachian tube.
This tube ventilates the ear and equalizes the air pressure in
the middle ear to the outside air pressure.
The
inner ear contains the hearing (cochlea) and balance (labyrinth)
organs. The auditory nerve connects the cochlea to the brain.
In
a healthy ear, sound waves striking the eardrum send vibrations
through the 3 tiny bones in the middle ear. Movement of these
bones transmits sound waves across the middle ear to the cochlea
of the inner ear. In the cochlea, sound is transformed into nerve
impulses that travel to the brain. In this manner, sound is perceived.
Last
updated on 23-02-2001
