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Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, I'm going to be talking about the calvaria. And what is the calvaria? This is basically the top ... Read more
Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, I'm going to be talking about the calvaria. And what is the calvaria? This is basically the top portion of your skull that has the shape of a helmet as you can see here on both of these images. We're just going to look at the different structures that we can find on the calvaria.
Now, on the right side, we're looking at the superior view of the calvaria while on the left side, you can see the inferior view if we were looking from below. Now notice that on the superior part of the calvaria, this structure is generally smooth with a few structures interrupting the smooth landscape such as sutures and foramina which we will talk about later on. From the superior and inferior views, we're going to see four bones specifically and they are connected to their adjacent bones via sutures that we're also going to cover. But these four bones are the frontal bone, the 2 parietal bones and the occipital bone.
Now, let's start by covering the bones then, and starting off this one highlighted in green, we're looking at the superior view of the frontal bone. And the frontal bone is one of the bones of the neurocranium which encloses, or the part of the skull that encloses the brain. This bone consists of 3 parts as well that we can define here. The squamous part which encompasses the area of the forehead. Another one is going to be the orbital part which you cannot see from these views – from the calvaria – but I'm just writing them down so every time you hear about the frontal bone you think about these parts for your next exam. And the next one is going to be the nasal part which we cannot also see clearly from the calvaria. So, here, we can mainly see the squamous part which is the area that forms or defines your forehead.
Now, we're going to briefly talk about the squamous part of the frontal bone which we're now looking at a sagittal cut here of the skull. And the squamous part of the frontal bone comprises the frontal sinuses which are located superior to the orbit on the medial side and are separated by a septum. But, on another tutorial, I want to take some time to talk about the different frontal sinuses and where they are located precisely but I just wanted to give you an idea of the squamous part of the frontal bone and also a bit of knowledge here that is important to know. Now, if we're still on the frontal bone, it's important that we just mention briefly a little bit about the orbital part of the frontal bone which forms the roof of the orbit and the ethmoid sinuses and you can clearly see here highlighted in green on the image on the right side.
Though not visible from the superior aspect, it is important to note here on this tutorial. And if we're covering all the parts of the frontal bone, it is important to also cover briefly the nasal part. And the nasal part of the frontal bone aids in the formation of the stem of the nose as the frontal processes of the maxilla and the nasal bones adhere to it, so they're connecting here. Notice here the maxilla – the processes of the maxilla – are connecting here with the nasal part of the frontal bone.
Now, let's go back to the subject here – the calvaria – to the superior view of the calvaria at the top of your head, and you can see here the suture – this long suture – that is known as the coronal suture. And the coronal suture connects the frontal bone – like we just talked about before – and also the 2 parietal bone – so, one parietal bone here and another parietal bone. And from the superior aspect, the coronal suture appears to run transversely.
Now, let's talk about the 2 bones that I just mentioned briefly – the parietal bones – and the parietal bones are found on the both sides of the neurocranium and are attached to each other via the suture here that we also are going to talk about – the sagittal suture – and to the frontal bone anteriorly via the other suture that we've mentioned briefly on the previous slides – the coronal suture here. And on the posterior portion of the parietal bones, you see they're connected here via the lambdoid suture that we're going to talk about with this other bone here, the occipital bone.
Located just between these 2 bones – the parietal bones – we're going to find the next structure that is known as the sagittal suture. And the sagittal suture runs perpendicular between the parietal bones at the midline of the skull and it joins the 2 parietal bones and located between 2 sutures – the one that we talked about before, the coronal suture here – and another one that we're going to be covering later on – the suture here – known as the lambdoid. So, the sagittal is just running perpendicular to these two sutures.
The next one – if you notice these two little holes here – they're known as the parietal foramina. And, on either side of the sagittal suture, we find the parietal foramina located on the posterior part of the parietal bones. And this is where the emissary vein transmits to the superior sagittal sinus. One suture that I already mentioned briefly is known as the lambdoid suture, and this suture connects the occipital bone which is this bone right about here – you can see it from the superior view of the calvaria – and the two other bones that we already talked about – the partial bones. And if I turn the calvaria to the inferior view, you can also see clearly the lambdoid suture.
Now, followed by the suture, we're going to talk about the bone that follows a bit more posteriorly, this is the occipital bone. The occipital bone covers the back of your head. This is the only cranial bone to articulate with the cervical spine and this bone is responsible for housing your cerebellum.
Still on the inferior view here of the calvaria, we find the frontal crest, and the frontal crest can be seen quite clearly here. This is formed by the edges of the sagittal sinus that unite forming a ridge that you can clearly see here highlighted in green. And here the falx cerebri attaches to the calvaria. Then, we find this one here, the sulcus of the superior sagittal sinus. This is a vertical groove found on the upper part of the midline and this is where the superior sagittal sinus is located.
Now, I'm going to highlight these really tiny structures – these dots that you can find on the inferior view of the calvaria – these are known as the granular foveolae. And these structures are found on the superior surface of – the inner surface – of the calvaria. They are pits that run along the course of the superior sagittal sinus and, in these pits, we find the arachnoidal granules through which the cerebrospinal fluid drains into the superior sagittal sinus. Now, this web here highlighted in green that also found on the inner or the inferior view of the calvaria, these are known as the arterial grooves that are formed by the meningeal arteries which course along the inner surface of the cranial vault.
Last part of our tutorial will be dedicated to this highlight here, this is the diploë, and this is a spongy layer of bone tissue found between the inner and outer compact bones of the cranium.
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Now, good luck everyone, and I will see you next time.