In this video I want to focus on some of the features of the brainstem.
And I will focus mainly on cranial nerves, but we will look at a few of the features.
So here we have a brainstem, and I have colored the cranial nerves yellow and some of the
other associated structures various colors.
On the top we can see here the head of the caudate, and then as we come down from the
caudate we are going to enter into the area on this model known as the mesencephalon,
which is basically on this model from the caudate down to the area of the brain stem
known as the pons.
This large bulbar area here is known as the pons.
The area that you can see between here our caudate and our pons, are known as the cerebral
peduncle's.
The cerebral peduncle's.
So we have the caudate.
The head of the caudate, more specifically, and the putamen to the sides.
We have the cerebral peduncle's.
Then we have the area known as the ponds.
Then we have the area known as the medulla oblongata.
Now we have 12 cranial nerves that we need to learn.
Only 11 of the cranial nerves come from the brainstem.
Cranial nerve one, the old factory nerve, does not come from the brainstem, so we do
not find it on this model.
Cranial nerve two is found right here.
Cranial nerve two is known as the optic nerve.
This is carrying visual information from the eyeballs.
However on this model it is important to notice, and I will tilt the model a little bit so
we can see underneath, I have here in yellow, the two optic nerves.
They come together, and I painted it green, in the area known as the optic chiasm.
From there the visual information travels back around the cerebral peduncle's to eventually
make it to the occipital lobe of the brain.
I painted that blue.
Those are known as the optic tracts.
So we have in yellow the optic nerve, in green the optic chiasm, and in blue, the optic tracts.
Just below the area of the optic chiasm there's little knob sticking out toward you, this
is the known as the infundibulum.
The infundibulum is the connection between the hypothalamus and the pituitary gland.
The pituitary gland is not seen on this model.
And wedged at the base of the infundibulum and between the two cerebral peduncle's we
can see two white little lumps here, those are known as the mammillary bodies.
Mammillary bodies act is really centers for the sense of olfaction, or the sense of smell.
So they are related to cranial nerve number one, although remember cranial nerve one was
not seen on this model.
So one is not seen, here we have two on either side of midline, at the junction between the
mesencephalon in the pons, the cerebral peduncle's and the pons, we see cranial nerve number
three.
Cranial nerve number three is called the oculomotor nerve.
The oculomotor nerve.
When we discuss movements of the eye we will talk more about the oculomotor nerve.
Then we can see wrapping around the brainstem, the only cranial nerve that actually leaves
the brain stem from the posterior aspect and wraps around to the front of the brainstem
is cranial nerve number four.
Cranial nerve number four is known as the trochlear nerve.
The trochlear nerve.
That nerve is also dedicated to movement of the eyeball.
On the lateral aspect of the pons we see a very large nerve exiting the side of the pons.
This is cranial nerve number five, also known as the trigeminal nerve.
Named the trigeminal nerve because it is going to split into three main branches.
So the trigeminal nerve.
Then as we go to the junction between the pons and the medulla oblongata, on either
side of midline we can really see a small nerve exiting and traveling up over the ponds.
This is cranial nerve number six, the abducens nerve.
The abducens nerve is also associated with movement of the eyeball.
Just lateral to the abducens nerve we see cranial nerve number seven.
Cranial nerve number seven is the facial nerve.
The facial nerve is involved in many different aspects, one of which is of course control
of muscles of facial expression.
Just lateral to cranial nerve number seven we have cranial nerve number eight.
The vestibulocochlear nerve.
Some folks used to call it the auditory nerve.
The vestibulocochlear nerve.
It goes to our vestibule or system for balance in the inner ear, and the cochlea where we
convert sound vibrations to nerve impulse in the inner ear.
So lined up in a row from medial lateral here at the junction between the pons and the medulla
oblongata we have cranial nerve six, seven and eight.
The abducens nerve, the facial nerve, and the vestibulocochlear nerve.
When we enter into the Medulla oblongata we have an area what we call the pyramids of
the medulla.
Kind of an inverted triangle.
Long tall inverted triangle.
One here and one here.
On those pyramids are a little area here that is probably beyond the resolution of this
camera, where there are some fibers crossing over, and a little roughened area here on
the model.
That is called the deecussation of the pyramids.
If we look just lateral to the pyramids on either side, we see on this model a large
pink spot, that is actually a lump on the side of the medulla oblongata, it is known
as the Olive.
It looks almost like an olive pit tacked onto the side of the brainstem.
And underneath the olive we will find a large collection of neuron cell bodies called the
inferior olivary nucleus.
That is what causes the swelling to the outside of this medulla oblongatta.
But for our purposes we can use that olive is a great landmark.
Because we still have to do cranial nerves nine, ten, eleven, and twelve.
Cranial nerves and nine, ten, and eleven leave this brainstem posterior to the Olive.
So here we can see, leaving posterior to the olive, cranial nerve nine, the glossopharyngeal
nerve, cranial nerve ten, the Vegas nerve, and then we drop a little lower, cranial nerve
eleven, the spinal accessory nerve.
Named the spinal accessory nerve because it also gets a little bit of input from the first
cervical nerve of the spinal cord.
So cranial nerve nine, ten, and eleven.
The glossopharyngeal nerve, the Vegas nerve, and the spinal accessory nerve.
Exiting the brainstem anterior to the olive we will see the fibers which make up cranial
nerve twelve, the hypoglossal nerve.
So let's look real quickly one more time at our cranial nerves.
Remember cranial nerve one not found on this model, it does not arise from the brainstem.
Cranial nerve two, the optic nerve.
Cranial nerve three, the ocular motor nerve.
Four, trochlear.
Five, the trigeminal.
Six, abducens.
Seven, facial.
Eight, vestibulocochlear.
Nine, glossopharyngeal.
Ten, vegas.
Eleven, spinal accessory, and twelve, the hypoglossal.
That olive separate nine, ten, and eleven from twelve.