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PRESENTER: Sound waves
entering the ear travel

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through the external
auditory canal

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before striking the eardrum
and causing it to vibrate.

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The eardrum is connected
to the malleus,

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one of three small
bones of the middle ear,

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also called the hammer.

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It transmits sound vibrations
to the incus, which

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passes them to the stapes.

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The stapes pushes in and
out against the structure

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called the oval window.

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This action is passed
on to the cochlea,

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a fluid-filled,
snail-like structure that

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contains the organ of Corti,
the organ for hearing.

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It consists of tiny hair
cells that line the cochlea.

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These cells translate vibrations
into electrical impulses

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that are carried to the
brain by sensory nerves.

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In this cut view, you can
see the organ of Corti

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with its four rows
of hair cells.

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There is an inner
row on the left

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and three outer
rows on the right.

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Let's watch this
process in action.

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First, the stapes rocks
against the oval window.

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This transmits waves of sound
through the cochlear fluid,

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sending the organ of
Corti into motion.

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Fibers near the upper
end of the cochlea

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resonate to lower
frequency sound.

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Those near the oval window
respond to higher frequencies.