The skull is divided into cranial bones and facial bones.
And the cranium is more of a sphere shape.
Helps protect the skull.
Whereas the facial bones are laid out such a way that we could have the nasal cavity,
and we can have two eyes pointing in the same direction, which aids in binocular vision.
And of course the mandible, the mouth for chewing.
So in this video I just want to run through the various bones of the skull.
The sutures that we require you to know.
And then we’ll look at some of the other features.
The foramen and some of the other things in the skull.
So let's take a quick look at skull overview.
I will do facial bones here in just a second.
Across the front of the skull we have what is known as the frontal bone.
Notice frontal bone forms a portion of the orbit of the eye.
So here we have frontal bone.
And if we can make a lateral view of the skull, the frontal bone meets, the frontal also being
an unpaired bone.
That means a single bone of the skull.
Embryologically it’s a paired bone.
But as an adult it should be an unpaired bone.
It meets with the two paired bones which form the top and lateral aspects of the skull,
which are called the parietal bones.
The suture between the frontal bone and the parietal bones is known as the coronal suture.
The coronal suture.
Now if I rotate the skull and look at a somewhat superior and posterior view of the skull we
can see the two parietal bones are separated by a suture known as the sagittal suture.
So in this view you can see a little bit of the frontal bone with its coronal suture separating
it from the parietal bones.
And the sagittal suture separating the parietal bones.
And then a little bit here we can see what is called the lambdoid suture.
If I tilt this skull up a little bit we can see the posterior portion of the skull is
made of the occipital bone.
Occipital bone separated from the parietal bones by the lambdoid suture.
And every now and then along the lambdoid suture you may see the suture make a little
loop and leave a small bone along the way.
Those are known as either wormian bones or also known as sutural bones.
Now if we come back and take a lateral view of this skull again, immediately below the
parietal bones we see a bone known as the temporal bone.
The temporal bone has an arch which reaches forward to the zygomatic bone.
It has a process behind the ear canal known as the mastoid process.
The ear canal itself is the external auditory meatus.
Some books call it the external acoustic meatus.
Notice that the temporal bone is separated from the parietal bones by the suture known
as the squamous suture.
Those are the four sutures that we are required to know in our A and P classes.
The coronal suture.
The squamous suture.
The sagittal suture.
And the lambdoid suture.
On this model I'm going to take a quick look at the face.
The first bone I want to talk about is called the mandible.
Sometimes known as the jaw bone.
The mandible.
It is a single, unpaired bone.
It houses the lower teeth.
And on the mandible we can see there's a small foramen, or opening, in the bone just off
midline on either side.
This is known as the mental foramen.
Then we have the main body of the mandible.
If I turn the skull laterally we can then see a flat area of the mandible known as the
ramus.
And there's an angle where we go from body to ramus.
And I'm going to lift the rest of the skull away for a second.
We can see on this mandible the coronoid process, important insertion point for the temporalis
muscle.
And then the condylar process which will articulate with the temporal bone to form the temporomandibular
joint.
If we look at this mandible from a medial view we can also see another foramen going
into the, into the ramus of the mandible.
So I'm going to put this back down and match it up with the skull for just a second.
And then we're going to move this out of the picture.
So here is our mandible associated with the skull.
Notice it fits in with the temporal bone to form the temporomandibular joint.
I remove the mandible.
I want to look directly into the orbit of the eye.
Directly into the orbit of the eye.
The orbit, also known as the eye socket, is made up of seven different bones.
Seven different bones.
And if we look carefully in this skull we can see the frontal bone.
We can see the ethmoid bone.
Which is actually a bone located between the two eyes.
The ethmoid bone.
This is called the orbital plate.
There's another orbital plate in the other orbit.
And the ethmoid bone also makes up a good portion of the internal portion of our nasal
cavity.
But we're going to look at that in just a second.
So we see the ethmoid bone.
The frontal bone.
Part of the maxilla.
Which is half of our upper jaw.
Part of our nasal cavity.
And now we know, part of our orbit of our eye.
The zygomatic bone.
The lacrimal bone.
And in the posterior portion of the orbit of the eye, the sphenoid bone.
There is another bone that helps make up the orbit of the eye.
The palatine bone.
However on this model they do not show you that portion of the palatine bone.
It is a very small portion of the orbit of the eye.
So if we look in the orbit again we will name the seven bones.
The frontal bone.
The ethmoid bone.
The lacrimal bone.
The maxilla.
The zygomatic bone.
The sphenoid bone.
And then the palatine bone.
I think I got all seven.
If we look into the orbit of the eye in a somewhat superior fashion I can see an opening
in the back of the orbit of the eye.
This is called the superior orbital fissure.
The superior orbital fissure is actually a gap between the greater and lesser wings of
the sphenoid bone in the posterior portion of the orbit.
Just medial to that we can see a foramen passing through.
That foramen is a feature of this sphenoid bone.
That is called the optic canal.
Some books call it the optic foramen.
In the lower portion of the orbit of the eye we can see the inferior orbital fissure.
The inferior orbital fissure is between the maxilla bone and the sphenoid bone.
Between the maxilla and the sphenoid.
So that represents the bones of the orbit of the eye.
Now I'm going to tilt the skull a little bit and will put the mandible back on.
I want to look into the nasal cavity for just a second.
The nasal cavity is actually made up of several bones.
But what is obvious on this model is the two maxilla on either side forming a portion of
the nasal cavity.
And then we have what is called the nasal septum.
The nasal septum is actually two bones.
The bottom portion is a bone called the vomer bone.
It is an unpaired bone.
Very thin bone, forming the lower half of our nasal septum.
The upper half of our nasal septum is part of the ethmoid bone.
It is known as the perpendicular plate of the ethmoid bone.
On the lateral margins of our nasal cavity we can see these rolled up areas.
These are known as the nasal concha.
The nasal concha.
We have a inferior, a middle, and a superior nasal concha.
On this model we cannot see the superior nasal concha.
The inferior nasal concha is its own separate bone.
So if you're counting the bones of the skull, inferior nasal concha is a bone.
And there is one on either side.
The middle nasal concha is part of the ethmoid bone.
And then the superior nasal concha that cannot be seen on this model is also part of the
ethmoid bone.
The superior portion of the nasal cavity is made up by two bones known as the nasal bones.
Tilt is down so we can see the nasal bones right here.
Nasal bones are separated from the lacrimal bones of the orbit of the eye by a portion
of the maxilla.
Now I want to talk about the inferior view of the skull.
We'll talk about some of the bones we can see and then we'll start to talk more about
various foramen of the skull.
On an inferior view here we can see, very large unpaired bone.
This is occipital bone.
And in the occipital bone we have a very large foramen known as the foramen magnum.
Foramen magnum is for the spinal cord exiting the cranial vault, and blood vessels associated
with the spinal cord and brain.
Immediately lateral to this foramen magnum we can see two smooth areas.
These are known as the occipital condyles.
The occipital condyles form the articulation between the occipital bone of the skull and
the very first cervical vertebra, known as the atlas.
So we will make the atlantooccipital joint.
Immediately lateral to this occipital bone we can see the inferior portion of our temporal
bone.
And here we can see that mastoid process that we have already talked about.
But we can also see a feature sticking out that looks a little bit like around toothpick.
That is known as the styloid process.
The styloid process is a feature of the temporal bone.
If we look carefully, I'll tilt the skull more, between the occipital bone and the temporal
bone we find an opening here known as the jugular foramen.
The jugular foramen.
That is for one of the jugular vein's exiting the cranial cavity to bring blood out from
the cranial vault.
Immediately anterior to that jugular foramen we see another opening here.
This is called the carotid canal.
Now the carotid canal is not a foramen.
It is a canal.
It goes into the bone and then it turns and it travels in a medial direction in the bone.
That cannot be seen on these plastic skulls.
You need a real skull to be able to see that carotid canal.
So let's switch out and take a look at the interior view of a real skull.
Here we can see our occipital condyles.
Our jugular foramen.
And now here we can see the opening of our carotid canal.
Notice it does not pass straight through the bone as the other foramen did.
But it will turn and go medially as a canal running through the temporal bone.
So you do not get to see the other opening, or the opening of the other end, on the superior
surface of the skull.
So the carotid canal should be looked at in both the real skull versus the plastic skull.
I'm using plastic skull mainly because it has the yellow lines between bones to help
you learn the different bones of the skull.
Here you can see, on the real skull, a good example of the styloid process.
It is very fragile.
It has been broken off on this side.
Let's switch back to our plastic skull and look at some of the other features.
The plastic skull now, we just finished with the carotid canal.
If we go medial and a little bit anterior to that along the very most anterior portion
of the occipital bone, we see another foramen, this is known as the foramen lacerum.
The foramen lacerum.
It is a foramen between temporal bone and occipital bone and a little bit of the sphenoid
bone.
Now on this skull we can see coming all the way across the bottom the features of those
sphenoid bone and it's pterygoid plates.
We can also see into the nasal cavity from a posterior view.
If you remember before, the nasal cavity is formed by the vomer bone and by the perpendicular
plate of the ethmoid.
You can't see the perpendicular plate of the ethmoid from this angle but we can see the
vomer bone.
Then I want to move into the roof of the mouth.
The bony portion is known as the hard palate.
The hard palate is made up mostly of the left and right maxilla, or maxillary bones.
And then the very posterior portion of the hard palate is formed from the left and the
right palatine bones.
So the palate, the hard palate, is mainly maxilla.
Only a part of it is formed by palatine bone.
And if we look carefully at the front, right in the midline between the two maxilla there
is a foramen known as the incisive foramen.
I have now removed the calvarium of the skull so we can look inside the cranial vault.
And again let's just go through and look at the bones.
Here we see the frontal bone making of the anterior portion of the cranial vault.
But in the very middle of the frontal bone here we see another bone sticking up from
the nasal cavity.
This is actually a superior view of the ethmoid bone, with a little crest of bone sticking
up known as the crista galli.
And on either side of that, a recessed area known as the cribriform plate.
So the crista galli surrounded by cribriform plate's.
Immediately posterior to the frontal bone we see the sphenoid bone.
Here is the lesser wing of the sphenoid bone.
And down here we see the greater wings of the sphenoid bone.
IN that sphenoid bone we can see the other side of what we saw in the orbit of the eye,
the optic canal.
Remember some books called it the optic foramen.
Immediately posterior to that we have an area known as the sella turcica.
Now the sella turcica is divided into four different regions, but in this demo we will
just refer to the sella turcica.
If we look just lateral to the sella turcica we come down and we can see the other side
of the foramen lacerum.
Remember we've seen foramen lacerum from an inferior view.
And then we see three foramen lined up in the sphenoid bone in the greater wing.
We have the foramen rotundum, which is traveling in an anterior posterior direction in the
sphenoid bone, to actually go out into an area just inferior to the orbit of the eye.
If we travel back and a little bit laterally from foramen rotundum we can see foramen ovale.
And then a very small foramen just posterior and lateral to that, known as the foramen
spinosum.
So foramen rotundum, foramen ovale, foramen spinosum.
Then we see a very large ridge in the temporal bone.
This is known as the petrous portion of the temporal bone.
Inside the temporal bone, in this petrous ridge, we will see all the mechanisms of our
middle and inner ear.
Mechanisms for balance, the vestibular system, and for hearing.
On the internal end of this petrous region we see the internal auditory meatus.
Some books call it the internal acoustic meatus.
And immediately below that, inferior to that, between the occipital bone and the temporal
bone, we can see the internal aspect of the jugular foramen.
Now I want to switch this out for a real skull and compare the plastic to the real.
Here is an internal view of a real skull.
And I'm going to turn it just a little bit.
Here we can see the frontal bone.
And right here we see the ethmoid bone with it's crista galli.
Right here, they should not be open.
This was the area of the cribriform plate.
It is very fragile.
So on this side of the skull it has been chipped away.
You can see most of it here.
There is a small portion chipped away.
The cribriform plate.
Immediately posterior to that we then have the sphenoid bone with the sella turcica and
the optic canal or optic foramen.
Again we can see in an anterior posterior direction foramen rotundum.
We come back to foramen ovale.
And foramen spinosum.
Here we can see foramen lacerum.
If I could go into the bone this way I would be inside the carotid canal.
I believe that is all of the features, or at least a majority of the features, that
you will be responsible for on the skull.