00:01
Again, let's go to a diagram for an explanation
of how this organ of Corti works. Have a look
at the hair cells. Outer hair cells and inner
hair cells, I'm not going to separate between
each of those. The hair cells are strongly
again supported by different supporting cells,
the outer and the inner phalangeal cells.
They wrap around the base of the cells and
they send the process up to link across near
the apex of the hair cells where the stereocilia
are. There are other supportive
cells there, the
pillar cells. They create a tunnel between
the pillar cells that support the inner hair
cells and the pillar cells that support the
outer hair cells. And then the hair cells
themselves have both afferent and efferent
terminals. The afferent terminals are again
from the ganglion cells in the spiral ganglion.
They're going to take information back to
the central nervous system from impulses that
these hair cells will send then those efferent
nerve fibres. These cells sit on the basilar
membrane. And the basilar membrane and the organ
of Corti itself is attached to the spiral
lamina. It's a thin projection from the
modiolus bone. So on the base is
the basilar membrane.
01:43
And the other very important point is that the
hair cells themselves are in contact or close
apposition to the tectorial membrane above.
That tectorial membrane again projects from
the bony modiolus. It's a gelatinous type
substance. And what is going to happen is
that on the base, on the basilar membrane,
when that starts to vibrate, it creates a
shear force between the tectorial membrane
and the hair cells. The tectorial membrane
actually touches those stereocilia. And that
touching of the stereocilia caused by the
vibration of the basilar membrane stimulates
a nerve impulse. And that nerve impulse is
used to detect sound and frequency and so
on, and it's processed by the central
nervous system. Well, let's have a
look at the real section,
a histological section through the organ of
Corti. And again, we can label the tectorial membrane,
almost in contact with the hair cells. Outer
hair cells sitting on the basilar membrane
there and the inner hair cells will sit on
there as well. And again, as I mentioned before,
when that basilar membrane vibrates due to
waves of fluid, the perilymph moving along
through the scala vestibuli and the scala tympani
created by the oval window, being stimulated
by the ossicles, this wave of fluid or wave
of vibration makes that basilar membrane vibrate
also. And as I explained, that vibration then
creates a force between the tectorial membrane
and the hair cells.