Let's, first of all, look at the general
anatomical structure of the ear. On this diagram,
there are various labels that do illustrate
all the major components of the ear. Starting
on the left-hand side is the pinna of the
ear. That part of the ear is very flexible.
We can twist and bend it and it will spring
back to its normal shape because it has got
elastic cartilage in it. That helps to locate
or amplify the sound but has very less function
in humans than it does in other animals. The
external auditory meatus is about two and
a half centimeters long. It is bound on the
most lateral part by the pinna of the ear.
And the very first third is supported by cartilage,
and that cartilage blends with the elastic
cartilage in the pinna of the ear.
The skin, lining the external auditory meatus,
has got special glands in it called ceruminous
glands. Those ceruminous glands secrete a
component that combines with apocrine secretions
to produce ear wax. And that ear wax is used
to try and trap any particular matter that
happens to find its way into that auditory
canal. And that ear wax is also suspended on
the fine hairs in that canal again to increase
the opportunity to trap that matter. On the
medial aspect or the end part of that auditory
tube is the tympanic membrane or the eardrum.
It vibrates in response to sound waves.
And those vibrations are passed on to the bony
ossicles, the malleus, incus, and stapes,
illustrated in the diagram. And those
bony ossicles will vibrate themselves,
and those vibrations will then be passed to
the oval window in the inner ear. The oval
window and the round window play a very important
role in the functioning of the inner ear.
You also have labelled there the auditory tube.
It's a passage going from the middle ear
cavity, all the way down to the pharynx. Normally,
it's closed, except when we swallow or maybe
when we yawn. It's a passageway or a potential
passageway for pathogens passing out from
the pharynx. Here are two diagrams
representing the structure