Hello, everyone! This is Joao from Kenhub, and welcome to another tutorial. This time, I’m going to be talking about the anterior and lateral views of the skull as you probably guessed by just looking at the title on the screen. Now, notice here that I’m showing you the anterior view of the skull, and we’re going to be covering different bones and landmarks seen here on the anterior view as well as on the lateral view of your skull.
Now, the very first thing that you notice here when you look at the anterior view of the skull is this structure that I’m highlighting right now in green, the viscerocranium. Viscerocranium has a scary name, but nothing to be scared about.
Viscerocranium is one of the two parts that we usually split the skull—so one of the two areas that make up your skull. It is located anteriorly to the other part that is not seen here highlighted that is known as the neurocranium. And the neurocranium is basically located posteriorly to the viscerocranium. And as you can see here, the neurocranium is going to be the area, the main area that encapsulates your brain while the viscerocranium is going to contain most of the bones that are responsible for your facial skeleton. So the viscerocranium comprises several bones that form the skeleton of the face as well as parts of the jaw.
Now we covered the viscerocranium, it is time for us to go over the list of topics that I want to be covering here on this tutorial. Before we go on and talk about it in detail, it’s always important to have some sort of list within our minds so we can know what we’re going to talk about.
Now, as I told you, we’re going to be covering the anterior and lateral views of the skull, but more specifically, we’re going to be focusing on nine bones that can be seen between the or on these two views. Now, this list includes the frontal, the nasal, the maxilla, the sphenoid, the mandible, the ethmoid, the parietal, temporal, and finally, your cheekbones, the zygomatic bones. Now, we’re going to look at all of these in more detail throughout this tutorial.
Also, another topic that I want to be covering is seen here on this scary image, and yes, I’m going to be talking about the bony orbit that can be clearly seen on an anterior view of the skull, and this is the bony structure that encapsulates all the structures of the eye.
Without further ado, let’s start with the very first bone here, highlighted in green. Now, this is the bone that defines your forehead and is clearly seen on the front view of the skull or the anterior view of the skull. And for the lack of better name, let’s just call it the frontal bone.
Now, the frontal bone is also divided in three parts that I would like to clarify here, just briefly mention them. First one is known as the squamous part, which is the large vertical portion of the frontal bone that defines the region of the forehead. Now, the other one is known as the orbital part, and the orbital part is the portion of the frontal bone which enters into the formation of the roofs of the orbital and also a bit of the nasal cavities. Now, last portion of the frontal bone is known as the nasal part, and the nasal part is the portion of the frontal bone that is articulating with these bones here, the nasal bones, and also the frontal process of the maxilla as you can see here. And this is basically the portion that helps form the root of the nose.
On this tutorial, I would like to give you some of the most relevant structures and also bony landmarks associated to the frontal bone. The first one is seen here, highlighted in green. This is a smooth and slightly elevated surface above the nasal root and is known as the glabella. The other bony landmark that we also find on the frontal bone is seen more specifically on the superior border of the orbit or the supraorbital margin, this portion right about here, where you find the structure that we’re going to mention now known as the supraorbital notch. This is an important structure because this is where the supraorbital blood vessels and nerve pass through.
Now, let’s move on to another bone found on our list. Now, this is a paired bone seen here, highlighted in green. And if you ever hear someone tell you that you have really nice cheekbones, then this is the bone that you need to thank them for, and it’s known as the zygomatic bone. Now, the zygomatic bone is also known as the zygoma, and as you can see here, this is one of the most complex bones of... or most irregular-shaped bones of your skull. Because we see them in pairs, they protrude laterally on your face, on your skull and form those eminences in your face that are known—it’s just a fancy way to say cheekbones.
Now, another thing that you need to know about the zygomatic bone is that it articulates with the frontal bone via the frontozygomatic suture.
So I would like to mention a few of the structures and landmarks associated to the zygomatic bone, and I’m going to start with these two seen here, highlighted in green. They are known as the frontal processes of the zygomatic bone. And as the name indicates, these are processes coming from the zygoma which will connect, then, the two bones, the frontal and the zygomatic bones. Now, what I also need to mention here is that the frontal process of the zygomatic bone actually contributes to the rounded shape or a rounded form of the bony orbit.
Now, the next one is a structure that is found on the temporal bone, but I would like to mention because this is what connects the temporal bone and the zygoma, and this is known as the zygomatic process of the temporal bone, which will connect, then, with this other process here known as the temporal process of the zygomatic bone. You know, in anatomy, we always keep things simple.
Now, these two bones are connected by this suture that you find right between them known as (guess) the temporozygomatic suture. Yes, this is… or the sutures are usually named after the two bones they connect—so, very simple to remember.
Now, the last structure that we’re going to be covering about the zygomatic bone are these two little holes that you find on both zygomatic bones. They are known as the zygomaticofacial foramen for singular and foramina for plural. Now, if we zoom in, we can clearly see them, and I can also show you that some nerves and vessels will pass through these foramina. Now, these are known as the zygomaticofacial nerves, and also, corresponding vessels will pass through the zygomaticofacial foramen.
Another bone that we find on the list of nine bones that we covered initially is this one seen here, highlighted in green. This is the bone that defines your nose. And as you probably have guessed, yes, this is the anterior and lateral views of your nasal bone. Now, the nasal bone is a bilateral, symmetrical paired bone of the face. So as you can see, you can notice here that there are two nasal bones. It’s a paired bone.
Now, their superior borders and main bodies form the bridge of the nose while the inferior borders connect with the nasal cartilage to, then, form the superior margin of the nasal aperture, which we will look at it with more detail on different tutorials.
Now, the next bone that you can clearly see here, now, highlighted in green, and this is known as the bone that is quite well-known, also seen here highlighted in green on the lateral view, this is the maxilla. And the maxilla is also known as the upper jaw and is a vital structure of the viscerocranium. It is involved in the formation of the orbit as well, the nose, and the palate, and holds the upper teeth and plays an important role for mastication and also communication. Without it, I could not be talking right now to you.
The first structure that I would like to cover about the maxilla is this one seen here, highlighted in green. It’s also a paired structure, and it’s known as the infraorbital foramen—foramina, plural. It’s located in the maxilla, underneath the orbital ridge and serves as the pathway for the infraorbital nerve and also the blood vessels.
On the anterior and lateral views of the skull, we’re able to see some of the projections of the maxilla, and these three of the four projections of the maxilla can be clearly seen, and they’re listed as follows: the zygomatic process, the alveolar process, and finally, the frontal process. And we’re going to talk about them in a little bit more detail, but this is just a quick list.
Now, keep in mind that the palatine process cannot be seen clearly from these two views as it is at a horizontal extension on the medial side of this bone. And then it forms the roof of the mouth and the floor of the nasal cavity. Now, that’s why we cannot clearly see the palatine process. If we were to use other views of the skull, then we could clearly see it, and we will do so in different tutorials. But I just wanted to list it right now for you so you know that this is also a projection of the maxilla.
Moving on, I want to talk about, now, some of the important structures and landmarks of the maxilla. One of them is a process that we just listed, the zygomatic process of the maxilla. And the zygomatic process of this bone grows laterally and then meets with another bone, the zygomatic bone.
The second process on our list is going to be this one seen also highlighted in green known as the alveolar process of the maxilla, and it is clearly an inferior extension of this bone, and it has a rather porous structure. The alveolar process forms what is known as the maxillary dental arch, which you cannot clearly see the shape here on these two images, but this is basically where you will find some cavities where the upper teeth are held.
The next one and last on our list is known as the frontal process of the maxilla, and the frontal process has a vertical ridge which constitutes the medial border of this structure here that we’re going to talk about later on, the bony orbit. And it’s clearly defining, somehow, the medial border of this structure.
Now, posteriorly, if you notice right about here, posteriorly, it forms the lacrimal groove together with the lacrimal bone. And superomedially—write this down. This is important—it is in close contact with the anterior ethmoidal sinuses.
The next bone on our list is going to be this one that I’m going to highlight right now, and this is not a paired bone although it does look like one here on the anterior view. This is known as the sphenoid bone.
And the sphenoid bone is the most complex bone of the human body. I mean if you look at different views of this bone, and we’re going to look at in different tutorials, this is a quite intricate bone but beautiful one to look at because it resembles a wasp. So it’s called, it is also known as the wasp bone, or to me, it looks somehow like a butterfly or something like that. It’s quite beautiful. And it makes up most of the middle part of the base of the skull and definitely contributes to the floor of the middle cranial fossa.
Now, important parts of the sphenoid bone, there are two that we need to talk about, the first one is seen here on the left side, highlighted on the left side, and this is known as the greater wing of the sphenoid. Remember, I talked about that. I just said that this resembles either a wasp or a butterfly, and we have to talk about the wings of course. And the sphenoid bone has two greater wings and also a lesser wing or two lesser wings.
Now, I’m going to let the wings of the sphenoid fly and move on to another bone here on our list—this one seen here, highlighted in green. This is the only bone in the entire cranium that doesn’t articulate with its adjacent skull bones via any sutures. So if you guessed it right, yes, this is your lower jaw, or a fancier name, the mandible. And the mandible, when you look at the skull purely as a bony structure, there is nothing automatically holding the rest of the skull and the mandible together.
Now, in terms of the articulations, we can notice here that the mandible is articulating here dentally. We call it a dental articulation. So the teeth that are rooted in the mandible are articulating with the maxillary teeth as you notice here. Another portion that will articulate or will form an articulation is known as the temporomandibular joint, which happens right about here. And this is an articulation happening between the mandible and also the neurocranium, more specifically, the temporal bone. And that’s why we call it the temporomandibular joint. You can see that we don’t have to clarify this point very much because it’s pretty simple, this name.
I would like to also show some of the landmarks and important structures related to the mandible. The first one is seen here, highlighted in green as well. I just changed the highlight. And this is known as the body of the mandible. And the body of the mandible is the largest part of this bone and is clearly seen from the anterior view and also the lateral views as you can see on both of these images, and the body is the horizontal part of the mandible.
Within the body of the mandible, we find the next structures that we’re going to briefly mention, the mental foramina—foramina for plural, and foramen for singular. Now, these little holes that you find within the body of the mandible are specifically found inferiorly to the second premolar tooth, and they do serve, let’s say, as exit points for certain structures including the mental artery and the mental branch of the inferior alveolar nerve.
Now, the next structure that we need to cover on the mandible, on this tutorial specifically, is known as the ramus of the mandible or rami because we have two—two rami. And these are two vertical parts of the mandible that are found posteriorly, but as you notice here on these two images, we can clearly see them from an anterior and lateral views of the skull. Now, these parts turn sharply upwards from the body, as you can see here that we talked about, just at the angle of the mandible, and they go all the way up as you can see here.
Now, moving on from the lower jaw to another bone here on our list, this one seen highlighted in green that is best seen anteriorly or on the anterior view of the skull—it’s known as the ethmoid bone. Now, this bone is sitting on the apex of the pyramidal stack of bones that defines the nasal opening, and you can clearly see here on this image. Now, you can also see that this is contributing, or the ethmoid bone is contributing to the medial wall of the bony orbit.
Now, this is enough on this tutorial about the ethmoid bone, and I’m going to move on to another bone seen here, highlighted also in green. And this time, this is a paired bone. That’s why you see two little highlights here on the anterior view, but you can clearly see this bone or these bones on a lateral view. These are known as the parietal bones, and they are found on both sides of the neurocranium, and they form large parts of the top and side of your head.
I want to use this opportunity to talk about some of the connections found between the parietal bones and other bones. The first one that can be seen here anteriorly is between the frontal bone and also the parietal bone, here, on both sides—the parietal bones forming this connection here that is known as the coronal suture. So the parietal bone is connected or borders with the frontal bone via the coronal suture.
The parietal bones are going to also come in contact with other bones laterally, and these include the temporal bones that you can see here connecting with the parietal bone via this structure here, the squamosal suture, and then the other structure that is going to be coming in contact with the parietal bone is the sphenoid bone right about here. You know, the sphenoid bone that we talked about is connecting right here through this structure, this suture known as the spenoparietal suture, which connects it to the parietal bone.
Now, let’s move on to another bone, another paired bone as you can see here and can clearly be seen on the anterior and also lateral views of the skull, this is known as the temporal bones. And the temporal bone is a large bilaterally symmetrical bone which forms the base of the cranial vault along with this bone right here, the occipital bone. And it also ascends to participate in the lateral walls of the skull.
Now, important to mention here on this tutorial that the temporal bone is articulating with other bones. Now, let’s look at the different connections here between the temporal bones… the temporal bones and other bones as well in the skull. The first one is one that we already talked about, the squamosal suture here connecting the temporal bone with the parietal bone. And then anteriorly, this suture is going to become the sphenosquamosal suture right here where the temporal bone is now in connection with the sphenoid bone, and then posteriorly, it becomes this suture right here that is known as the parietomastoid suture—this is a tongue twister I must say—which is the portion of the temporal bone here, the mastoid process that is connecting, then, with the parietal bone, as you can see here. And that’s why we call it parietomastoid suture.
The next point I want to make is just a reminder from when I talked about the zygomatic bone. When I talked about the temporozygomatic suture, which means that the temporal process or the zygomatic process of the temporal bone, right about here, is going to connect with the zygomatic bone via or articulate via this suture—the temporozygomatic suture.
Throughout this tutorial, I have been mentioning a few sutures which are fibrous joints connecting the bones of the skull. I would like to add a quick note on the most prominent suture seen from both the anterior and lateral views of the skull, and I will cover all the sutures on a different tutorial and training unit. But notice here this structure now that is highlighted in green. Just as a reminder, this is the coronal suture. And like I mentioned before, this separates the frontal bone from the parietal bones.
Now, it’s time for us to move on and talk about the last topic on our list on this tutorial. One of the things we clearly notice when looking at the anterior view of the skull is this structure that you see on your screen known as the bony orbit. And the bony orbit is a skeletal cavity that is made up of several cranial structures and surrounds the soft tissue that makes up your eye.
Now, it is important to mention that the bony orbit is divided into four main parts. The first one is known as the roof. The second one is the lateral wall, the medial wall, and the final one that we’re going to be covering is known as the floor of the bony orbit. What we’re going to do on this tutorial is to look at each individual structure or part of the bony orbit and define which bones or which part of the bones are defining this specific portion of the bony orbit.
And let’s start off with the roof, the roof of the bony orbit, and this one is definitely not on fire. Well, the roof of the bony orbit is comprised of this structure here anteriorly, which is the orbital surface of the frontal bone. Now, the other one is found more posteriorly, and if you remember this well—remember the wings?—yes, this is the lesser wing of the sphenoid bone, which comprises also the roof of the bony orbit.
Moving on to the second one on our list, this is the lateral wall of the bony orbit. It is comprised by the orbital surface of the zygomatic bone, seen here on the left side, and also a wing of the sphenoid; this time, the greater one. So the greater wing of the sphenoid bone also participates in defining the lateral wall of the bony orbit.
Moving on from the lateral wall of the bony orbit, we’re going to, now, start talking about the second one, the medial wall. And the medial wall is defined by this structure seen here highlighted in green. This is part of a bone, and more specifically, this is the orbital plate of the ethmoid bone that can be clearly seen here on the anterior view of the skull.
Now, also this bone seen here, if you remember well, this is the winged bone known as the sphenoid and will also contribute to the medial wall of the bony orbit. Still on the medial wall, there are some structures that will also be contributing to defining the structure of this wall, and one of them is seen here, highlighted in green, on the lateral view of the skull. If you remember well, this is the lacrimal bone. There will be small contributions of other bones, including the frontal bone as well as the maxilla.
Finally, we’re going to move on to the floor of the bony orbit which is defined by this structure here. This is found on the anterior part of the floor, and it is known as the orbital surface of the maxilla. Now, also, you’re going to see that, posteriorly, it is going to be defined by the orbital process of the palatine bone, which is difficult to see from this perspective, but I just wanted to include also here on this list. Anteriorly, the orbital surface of the zygomatic bone will also complete or help complete this area of the bony orbit.