Download Ear [screen displays a model of the ear] [voice of Dr. Barbara

Ear.rtf
[screen displays a model of the ear]
[voice of Dr. Barbara Davis, Instructor, Biology, speaking] Welcome to the sensory lab. In this
video we’ll be looking at the ear. The outside portion of the ear is called the auricle. The
opening into the external auditory canal is called the external auditory meatius. The meatius is
the opening and the canal is the tube-like structure that runs through the bone, so this is the
external auditory canal. All of these structures are part of the external ear. The external ear ends
at the tympanic membrane or the ear drum, and then behind the ear drum in this cavity, this
space here, this is the middle ear. So we’ll be looking at the middle ear a little bit closer here in
just a minute, but I wanted to point out this tube that runs from the middle ear, this is called the
auditory tube, and it uh, runs to the nasopharynx and it provides pressure release for the uh, air
inside the middle ear cavity. So the middle ear cavity here, is only connected to the external
environment through this auditory tube, which primarily is collapsed. Ok, at this point, we’re
going to zoom in to see the remaining structures.
[screen displays a closer picture of the inner ear]
Ok, here we can see is the middle ear cavity. The middle ear is located between the tympanic
membrane that is shown here, and uh, inside the temporal bone, underneath this area here that
looks like the stirrup, that’s the beginning of the inner ear, so the inner ear is all of this area here,
contained within the bone. First, let’s go back to the middle ear. Here in the middle ear. Sound
waves vibrate the tympanic membrane, which transfers that vibration to these three bones. The
first bone is called the malleus, because it’s shaped like a mallet. This bone then transfers the
sound waves to the incus, with the slim extension. Incus means anvil, so it’s shaped like an
anvil, and then this bone would vibrate and transfer the vibrations to the last ossicle, which is the
stapes. So we don’t want you to miss the middle ear ossicles, so from superficial to deep is
malleus, incus, stapes. “M-I-S”, don’t miss these bones. Now to see these structures a little bit
better, let’s lift out the tympanic membrane; you can see the tympanic membrane a little bit more
clearly there now. And we want to look now at the inner ear structures. The inner ear begins
with this oval-shaped structure at the base of the stapes. So this oval shape here is called the oval
window. The stapes vibrates and transfers the vibrations to the fluid just on the other side of the
oval window. Now, there’s two fluid-filled compartments in the inner ear, the structures we’re
looking at here contain endolymph. These are the semi-circular canals, the semi-circular canals
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Ear.rtf
at their base have ampula, that pick up information about head rotations that help with balance.
And over here, this sea-shell shaped structure is called the cochlear duct. The cochlear duct has
hair cells that contain information or that transfer information on hearing. So we have the
cochlear duct, and the semi-circular ducts. Information from these uh, areas are transferred
through this yellow structure, which is cranial nerve VIII, the vestibulocochlear nerve. If we lift
these structures out, you can actually see now that there are some indentations that are left in the
bone. These indentations on the side here where the semicircular ducts were located, is called the
semi-circular canals. Remember a canal is just a uh, tube-like structure that runs through the
bone. So these are the semi-circular canals. On this side, where the cochlear duct was sitting,
uh, this indentation here is called the cochlea. The cochlea. And this completes our study of the
ear.
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KC
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