Hello, hello, everyone. This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, I'm going to be focusing on the posterior and lateral views of your skull. And what I'm going to be doing is looking at the lateral view and also the posterior view of the skull and describing the different structures that can be seen from these views. So on your right side, you are looking at the lateral view, and on the left side of the screen, you can see the posterior view of the skull, and we’re going to try to describe all these structures that are important.
Now, as I mentioned, we’re going to be focusing on different structures and I want to list them before we move on and talk about the different details. And these structures include several sutures that can be seen from these views. And also, we’re going to highlight different bones and their related landmarks.
Now, let’s start with the very first topic here on our list, the cranial sutures. And we’re going to just go over the different cranial sutures that you can find on both the lateral and posterior views of your skull.
Now, before we do so, I want to clarify and make a quick definition of what a cranial suture is. And a cranial suture is a type of syndesmosis that shows where the cranial bones will articulate, and sutures remain open for a while as your body grows and develops, because as the brain expands during growth, the cranial sutures expand along with it. So there is an advantage right there. And here on this image, you can see on the right side that there is a highlighted suture that we’re going to be covering just for an example here. But we’re going to be covering it later on on this tutorial. Important to add that the cranial sutures will ossify at different stages of your life.
And knowing that, now, you have some clear idea of what a cranial suture is. Now, we can talk about the different ones that you can find, now, for example, on the lateral side of your skull. And you can see this one highlighted. This is known as the sphenofrontal suture. And it’s a transverse suture found between the greater wing of the sphenoid—so this is the greater wing of the sphenoid—and the frontal bone. So this is an articulation happening between these two bones. And as you can see also, the name helps a lot because it’s describing the two bones that are articulating through this suture.
Now, also important to notice here, I'm going to give you, for reference, an anterior view of the skull where you can slightly see, here also, these sutures, the sphenofrontal sutures, seen on both sides of the skull.
Let’s carry on to the next suture, now seen highlighted here in green. This is known as the sphenoparietal suture. And if you guess well by the name, this suture is located between the sphenoid bone, as you can see—the sphenoid—and the parietal bone, you notice here. And important to notice that this suture is part or makes part of the region known as the pterion.
And you may be asking, “What is the pterion?” And this is a region found on the lateral aspect of the skull where the frontal bone, the greater wing of the sphenoid bone, and the temporal meet, as well as the sphenoparietal suture. So you have here the sphenoid, the parietal bone, and the frontal bone, so they’re all meeting here. And also, you can see the temporal bone, which are all part of the pterion and the suture that we just discussed, the sphenoparietal suture.
The next suture that we’re going to be discussing is this one now seen highlighted. This is known as the sphenosquamous suture. And this suture is found between the sphenoid bone and the squamous part of the temporal bone. And I'm showing you also an anterior view for reference. So, as you can see, it’s connecting the temporal bone here—this is the temporal bone—and the sphenoid right here.
The next suture on our list is going to be the squamous suture, the first suture that I showed you when I was clarifying or when I was giving you the definition of what a suture was. And this suture is located between the squamous part of the temporal bone, as you can see here—this is the squamous part of the temporal bone—and the parietal bone, this bone here. Now, it arches posteriorly from the area of the pterion, which is right here, that area that we just talked about.
Now, let’s move on to the next suture on our list, a well-known and relatively large one. This is known as the coronal suture. And the coronal suture is separating the parietal bone or the parietal bones, because you have one parietal bone on each side of your skull, and this bone here, the frontal bone. Now from the lateral view, it appears as a vertically running suture, but if we also look here on the anterior view of the skull, you can see that the suture is going to go from one side of the skull all the way to the other side. The coronal suture, on an average human, ossifies between the age of 30 to 40 years old.
The next one on our list is going to be this one, also highlighted in green, and this is known as the lambdoid suture. And this suture, although best seen from the posterior view—and I have here a posterior view so you can clearly see the lambdoid suture—can also be seen on the lateral view on the right side, on the image on the right side. And you can clearly see the suture on the cranium. It connects the parietal bones as you can see here: one parietal, two parietal bones, and the occipital bone here. So this is the articulation that is happening between these three bones. This suture ossifies between the ages of 40 and 50 years of age.
Now, let’s take a look at the next suture in our list, this one here, a relatively small suture known as the frontozygomatic suture. We can also call it zygomaticofrontal suture. And you can clearly see by the name as well that this… this suture is connecting this bone here, if you guess well, the frontal bone or the bone that defines your forehead, and this bone here that defines your cheeks. This is your cheekbone known also as the zygomatic bone. And I have here an image of the anterior view of the skull where you can clearly see the frontozygomatic sutures on either side of the skull.
Now, let’s move on to the next one, next suture here. And this one is the last one that we’re going to be covering known as the sagittal suture. And part of the sagittal suture can be also seen from the posterior view of the skull. It connects two parietal bones as you can see also: one, two parietal bones. It runs anteriorly from the coronal suture to the lambdoid suture posteriorly—this suture here that we just talked about in a few slides before. It is also known as the interparietal suture. We can also call it since it is between… found between the two parietal bones. The suture typically ossifies between the ages of 20 and 30 years of age.
Now, it is time that we complete and wrap up the sutures and move on to the next topic on our list: the bones and related landmarks that we can find on both the lateral and posterior views of the skull.
Let’s start off with the bone that you can see now, here, highlighted in green. This is known as the cheek bones or the zygomatic bone. And the zygomatic bone is comprised of three processes: the frontal process, the temporal process, and the maxillary process. And I'm going to show you where you can find these processes. So, frontal process, here, connecting with the frontal bone. You have the maxillary process connecting with, then, the maxilla. And you have the frontal process here, this protrusion that is connecting with this bone here, the temporal bone.
Now, the next structure that you can clearly see from the lateral view of the skull is this one, seen highlighted in green. This is known as the zygomatic arch. And the zygomatic arch is formed by two processes, one coming from the temporal bone—this is the zygomatic process of the temporal bone—and another process coming from the cheek bones or the temporal process of the zygomatic bone. These two processes are going to meet here and form this bridge or this arch known as the zygomatic arch.
The next structure that we’re going to be talking about is a bone. This bone is known as the maxilla and also known as the upper jaw. The maxilla is involved in the formation of the orbit, the nose, and also your palate. It is a vital structure of the viscerocranium, in other words, the skeleton that defines the face and houses the upper teeth.
The next structure that we’re going to be talking about that is part of the maxilla. This is known as the palatine process of the maxilla. It’s a thick horizontal process of this bone. It forms the anterior three-quarters of the hard palate. And the horizontal plate of the palatine bone makes up the rest of the palate.
The next structure that we’re going to be talking about is this one here, a foramen. This is the incisive foramen. And the incisive foramen is located on the maxilla and is found on the midline, posterior to the upper incisors. This is where the nasopalatine nerve and the greater palatine vessels pass through.
Moving on to the next bone here that we can see from a posterior view of our skull, this is known as the palatine bone. And for a… or from a posterior view on our image, we are able to see a bit of the palatine bone. And the palatine bone is a paired L-shaped bone that forms part of the nasal cavity and hard palate. It is located between the maxilla and the sphenoid.
The next structure that we’re going to be seeing on both the lateral and posterior views of the skull, but now seen here on the lateral view, is your lower jaw. This is known as, for technical term, as the mandible. And the mandible is the only bone in the entire cranium that does not articulate with its adjacent skull bones via any sutures. The only connection happening between the mandible and this bone here, the temporal bone, is here with the temporomandibular joint, and also there is a dental articulation here with the teeth from the maxilla.
Other structures that we can clearly see from the lateral view of the mandible are two processes, one is the condylar process and the other one is the coronoid process of the mandible.
Another group of structures that we can see here that we’re just going to briefly highlight so you can know where you find and how you can see them clearly from a lateral view of the mandible, but if you want to learn more about these structures in particular, I suggest you go and watch the tutorial on the mandible. But the structures you can see here on the lateral view of the mandible are the ramus. You can also see here the body, the angle of the mandible. See here the mental foramen, the mental protuberance, and also the alveolar process. Now, the alveolar processes are containing the teeth of the lower jaw and can also be clearly seen on the lateral view of the mandible.
Now, let’s take a look at the posterior view of the mandible. And now, this image is not highlighted, but I can show you this, here, is the mandible, and now, we’re looking at it from a posterior view. And what happens here is that we can also see other structures here that we need to highlight some of the structure that we just mentioned on the previous slide. And these are the ramus, the body of the mandible can also be seen from a posterior view, the angles of the mandible on each side can be seen, the mental spines, the sublingual fossa, which is going to be a place that will house the sublingual gland and the mandibular foramen, as well as the mylohyoid groove.
Let’s move on to the next structures here that we find on the posterior view, and this one is one that we just mentioned on the previous slide that we can see on the posterior view of the mandible, this is the mandibular foramen. And the inferior alveolar nerve and branch of the mandibular nerve passes through the mandibular foramen. Also, the inferior alveolar vessels pass though this foramen. It is located on the medial side of the ramus of the mandible, and you have one mandibular foramen on each side.
The next structure that we can see on both sides, the lateral and posterior views of your skull, are the parietal bones. Yes, because you do have two parietal bones. They are found on both sides of the neurocranium. The two bones meet at the midline of the skull and are connected by one of the suture that we talked about before, the sagittal suture. And anteriorly, the parietal bones border with the frontal bone, and posteriorly, they border with the occipital bone, as you can clearly see here on this image. So this is the border with the occipital and the border here with the coronal suture in the middle, with this bone here, the frontal bone.
They also border with the temporal bone and the sphenoid bone as you can see here: the sphenoid and the temporal forming a border laterally with the parietal bones.
Now, let’s move on to another bone that you can see on the lateral side, clearly from the lateral side and also a bit from the posterior view of the skull. And this is the temporal bone if you remember correctly. And the temporal bone is a large, bilaterally symmetrical bone, which forms part of the base of the cranial vault. It can be divided into four parts, and these are the squamous part, the tympanic part, the styloid process, and the petrous part.
Now, let’s take a look at the squamous part, here, of the temporal bone, seen highlighted in green. And the squamous part on the temporal bone can also be further divided into three parts: the temporal part, the zygomatic process that we talked about, and also the glenoid fossa, or we can also call it the mandibular fossa. This bone builds the lateral wall of the middle cranial fossa, and the glenoid fossa articulates with the mandibular condyle and forms the temporomandibular joint, right here. If you can see, this is the temporomandibular joint.
The next structure is one that belongs to the temporal bone, known as the styloid process. And the styloid process is a spine-like projection, as you can see here on this image, protruding from the inferior aspect of the temporal bone. It arises just anterior to the stylomastoid foramen which harbors the facial nerve and the stylomastoid artery.
Next in line is going to be this structure also found on the temporal bone known as the mastoid process, and we can see it both from the lateral and posterior views of the skull, and is located behind and slightly inferior to the external acoustic meatus. Muscles that will attach to this process include the sternocleidomastoid muscle.
Moving on to the next structure on our list, also a bone, the occipital bone that we already talked about. And this bone covers the back of your head, and makes up a large part of the basilar part of the neurocranium, and houses a structure, the cerebellum. This is the only cranial bone to articulate with the cervical spine.
Next is going to be this structure here, highlighted in green, also found on the occipital bone, and it is known as the external occipital protuberance. And this is a palpable protuberance found on the occipital bone. You can feel it if you touch the back of your head, and it feels on the midline. It lies on the midline of the external surface of the occipital bone and is where one muscle is going to attach to, namely the trapezius.
The next one is a line. This is known as the highest nuchal line. And as the name indicates, this is the nuchal line that is located above all the others, sometimes referred to as Mempin Line. And this is where a structure is going to attach, which is the galea aponeurotica.
Slightly below the highest nuchal line, we’re going to find another line, the superior nuchal line, and the superior nuchal line extends laterally from the external occipital protuberance that we talked about. And here, several muscles will attach to this line include the occipitalis, the splenius capitis, the trapezius, and the sternocleidomastoid. They will attach to this line.
Located below the previous two lines that we talked about, this is the most inferior of all of them, and we will then call it the inferior nuchal line. And this line is… is running inferior to the superior line, the superior nuchal line. And one muscle is going to insert just above this line, and this is the semispinalis capitis.
Next structures that can also be seen on the posterior view, a little bit from the posterior view of our skull here, are the occipital condyles. You have one on each side, and you can clearly see here on these… on this image that there is one occipital condyle on each side, and these protrusions are located lateral to the foramen magnum. These two protuberances are kidney-shaped and articulate with the first cervical vertebra forming the atlanto-occipital joint.
Next structure that I'm going to be showing you here is a foramen. This is known as the mastoid foramen and can be seen here on the mastoid portion of the temporal bone. The emissary vein is transmitted through the mastoid foramen as well, in some cases branches of the occipital artery.
Next one is known as the external acoustic meatus. And the external acoustic meatus is an orifice found on the tympanic part of the temporal bone and is the entrance to the middle and inner ear.
Next in line is this structure. Now, looking at the posterior view, you can see a bit of the pterygoid processes of the sphenoid. And one process on either side can be seen which descend perpendicularly from the regions where the body and the great wings of the sphenoid bone unite.
The last structure that we’re going to be covering here on this tutorial on… seen now on the lateral view, clearly seen here on the lateral view, this is an important structure and worth mentioning always, the temporal fossa. It’s a shallow depression on the side of your skull that is bounded by the temporal lines and terminating or ending below the level of the zygomatic bone. Bones involved in this temporal fossa boundaries include, right here, the frontal, and you can also see the parietal bone, the temporal bone, the sphenoid, and also the zygomatic bones are involved in forming the boundaries for the temporal fossa. And this is an important structure because several structures will attach here including the temporalis muscle.