The human ear is made up of three divisions: the
outer ear,middle ear, and inner ear. The outer ear catches sound waves and
transports them to the eardrum, a membrane that stretches across the outer canal
separating it from the middle ear. Sound waves cause the eardrum to vibrate. The
middle ear contains three very small bones called the hammer, anvil, and
stirrup. These are the smallest bones in the body. These bones accept the
vibrations from the eardrum and transmit them to the oval window, one of two
small membrane-covered openings between the middle ear and the inner ear. The
inner ear, which is entirely encased in bone, has a fluid-filled structure
called the cochlea, so named because it resembles a snail in shape.
The cochlea has numerous canals that are lined with
hair cells. The vibrations from the oval window are transmitted to the hair
cells in the cochlea and thence on the auditory nerve, which conducts the
vibrations to the brain. In the brain, signals are interpreted into sounds.
