You see simply some of this communication. For example, here you see an emissary vein that keeps in communication the venous sinuses with the veins outside of the scalp, for example. And here is the communication with some of the veins which are at the base of the scalp. So the communication of the emissary veins can take place with the veins of the scalp. scalp, sorry, but also with a venous system that is located at the base of the scalp, parietal, occipital, posterior condylar veins.
Now let's go back to our parietal bone and maybe in this old drawing, this is from a very old edition of the gray, you can see what I was trying to tell you before that there are two lines, the inferior temporal line and the superior temporal line. Here I would say they are clearly visible. And this superior temporal line and inferior temporal line, they limit superiorly what is called the temporal fossa or the fossa temporalis, which is one of the exocranial fossa, and that is called fossa. temporalis because it largely contains is occupied mostly by the temporalis muscle. Also sorry I was forgetting it this part of the parietal bone above the linea temporalis superior is covered this region is covered by what we already mentioned one by the galea capitis or galea aponeurotica.
Remember deep to the skull, sorry, deep to the dense connective tissue there is the aponeurosis, okay, that can also be called galea capitis or galea aponeurotica. And this galea capitis, okay, you see it's largely over the parietal bone, okay. And this galea capitis is in between the two bellies of the occipital frontalis muscle. So maybe you also understand now that if I cut the galea capitis and the two muscles contract as they normally do, so the wound that I do in the galea tends to be very much open, also because of the action of the muscles. Okay, the fossa temporalis, now this is the temporalis muscle, is one of the masticatory muscles, it's a very powerful muscle, and finds its origin here at the level of the inferior temporal line.
But then this muscle is contained in a, well, it's covered by a sheet of connective tissue, the fascia. of the temporalis muscle and the fascia is attached a bit superiorly to the inferior temporal line. So the inferior temporal line is for the muscle, the superior temporal line is for the fascia, and the temporalis muscle occupies most of the fossa temporalis of temporal fossa.
Now, in this fossa temporalis, which is basically this area that I'm showing you, the fossa temporalis, which are the bones that contribute to the floor of this fossa? Yes, the parietal bone, yes, because we just said it. But the parietal bone is here, right? And here we see the two lines.
But then, if I go more inferiorly, I also find the... Yes, the squamous portion of the temporal bone, very correct. And I find also, again, the greater wing of the sphenoid bone. So the temporalis muscle lies on the floor of the temporal fossa, which is provided by, yes, the parietal bone, but also the squamous portion of the temporal bone and the greater wing of the sphenoid bone.
And inside this fossa temporalis we find the muscles, but we find also vessels, and we find also, for example, nerves. This one here. auriculotemporal nerve. This is a branch of the mandibular division of the trigeminal. Or we find this one here that is called zygomaticotemporal nerve.
And this is a branch of the orange maxillary division of the trigeminal. Ah yes, that was the reason why I was mentioning this. One of the reasons I'm mentioning the auriculotemporal nerve, besides from the fact that in this way I bring together some information about the temporal fossa, so in the temporal fossa I find the temporal muscle, I find, for example, the auriculotemporal nerve, the zygomatic temporal nerve, is that the auriculotemporal nerve is a branch of the trigeminal, yes, mandibular division, but it's not only sensory. Because, as we shall learn together somewhere that I don't know as yet where, it also contains some visceral motor fibers for the parotid gland. You know that you have a parotid gland.
Can you point to me more or less where is it? Where is your parotid gland? Here.
Yeah, here. Okay. not on the outside, on the inside. That's the parotid gland.
And the parotid gland being a gland needs to be controlled by the autonomic nervous system. For example, by parasympathetic fibers and these parasympathetic fibers in a complex way that we are not going to discuss now, reach the parotid, but we will have to discuss somewhere. So at some point we will have to make this decision.
They are going to reach the... gland via the auriculotemporal nerve. Now, what about if we look at the parietal bone from the inside?
The inside seems a bit more complicated, sizzled somehow. What can we see here? Well, first of all, we see the sulcus for the middle meningeal artery, okay? For the right. origin for the stem of the middle meningeal artery and for its branches.
Now, I think that you realize here that if there is an imprint on the bone, it means that the artery must be really very close to the bone, right? Which is something clinically relevant for us to remember. So the groove that are formed for the middle meningeal artery and its branches. Okay, then Then we see again the sulcus for the sigmoid sinus. So we saw a sulcus for the sigmoid sinus in the petrous portion of the temporal bone.
But now we see that there is also in the parietal bone, so it's a long sinus. It doesn't run only where there is the temporal bone, but also where there is the parietal bone. And then we find here.
That's difficult. Sulkus, half sulcus for the superior sagittal sinus. Let's, yeah, let me use this image first. Now you have to know that one, the largest of the venous sinuses that we have in our skull is called the superior sagittal sinus. You see why it's called sagittal?
Because it's on the midline and it's called superior because... it's up there to distinguish it from the inferior sagittal sinus. Now, this superior sagittal sinus, well, is usually the lamination of the dura mater.
And during its formation, it leaves a groove both on the parietal bone on the right side and on the parietal bone on the left side. That's why when we, okay, anyway, this is the superior. oops sorry sagittal signs okay where are we here no here so we find here part of the groove for the superior sagittal sinus and related to this groove we find some depressions with a funny name pacchioni depression and they are called depression because there there are the so-called granulations of pacchioni which is where most of the cerebrospinal fluid is reabsorbed into the venous stream. Okay, story of the cerebrospinal fluid produced from the choroid plexuses.
it fills the ventricular cavities, then it exits at the level of the fourth ventricle and enters in the subarachnoid spaces and then it must be reabsorbed somewhere. It's mostly reabsorbed at the level especially of the superior sagittal sinus where we have those granulations. Yes? The Pacchione depression are depressions which are close here to the groove. Okay, they're really close to that here.
Let me, yeah, for example, this is a bit better, even though it's an older book, which you can appreciate from the drawing. So you see all these depressions here? That's where the granulations are.
Yeah, so an older drawing, but a better drawing, if you will. And here we see, well, what I showed you before, the soup. superior sagittal sinus and close to it the granulation where there is the reabsorption of the cerebrofinal fluid.
So just to remind you, what are those dural venous sinuses? The dural venous sinuses are venous channels located intraclinally between two layers of dura matter. So if I treat a dural venous sinus in like in histological evaluation and I make a section. What is the wall? How is the wall of this venous sinuses?
Are they like the other veins? No. In the sense that there is an endothelium lining them on the inside because there is blood inside, but when I look at the rest of the wall, rather than being made by the layers that we find normally in a vessel, it's made by the meninges, the dura mater. Okay?
So it's a delamination of the dura mater. This delamination keeps delaminated the endosteal layer and the meningeal layer. The endosteal layer is the layer of the dura mater, which is on the side of the endosteum, and the other one is the one that gets separated. This video is nice, but we are not going to look at it together. So where do we find this venous sinuses in the skull?
Well, we mentioned now the... superior sagittal sinus. And that's where this large layer of meninges that is called the great cerebral falx attaches on the skull. But we find venous sinuses, for example, also in the free margin from areas of meninges.
For example, this one here is the free margin of the great cerebral falx. And you see there's a sinus also there. That's the inferior sagittal sinus.
But we also find venous sinuses where one layer of meninges, of dura mater, inserts on another layer of meninges. For example, here we are seeing this layer of dura mater, the great cerebral falx, as it attaches on this territory of dura mater, which is called the tentorium cerebelli. And also here we find the venous sinuses.
So, bottom line, the venous sinuses are not only there where the dura mater attaches to the bone, okay? Well, most of them are, but some of them are also where there is a free margin in a layer of dura mater or where the dura mater attaches to another region of dura mater. Now, a few words about the middle meningeal artery, because the middle meningeal artery is very interesting from the clinical point of view. So I made you notice before that if I see all those imprints in the bone, it means that it's very close to the bone, the vessel. And this middle meningeal artery.
is a branch of the maxillary artery. So you see that the maxillary artery really is one of those vessels that one needs to remember. And this middle meningeal artery enters in the skull through a foramina that you don't know as yet where it is, but it's called the foramen spinosum. It enters in the skull and starts to run on the internal surface of the skull, leaving an imprint. So fine, so fine.
But So we are here more or less, so we are looking at the skull from the outside now. So imagine to have an x-ray view and imagine that behind these bones there are the branches of the middle meningeal artery. running on the inside surface of the skull. Now the problem here that, and some of you might remember it, that in this territory where the parietal bone, the squamous portion of the temporal bone, the greater wing of the sphenoid bone, the squamous of the frontal bone come together, we have a region where the skull is quite fragile.
This region, which is a circle here, which I did circle, I think, with a dashed line, is called the pterion. An important point of the lateral surface of the skull. So the middle medial artery travels underneath the pterion, where the skull is at its weakest and therefore is more reliable to break.
if I take a blow to the side of the head. So, if you want to know exactly where the diphtherion is, you put one finger, vertical finger, parallel to the lateral margin of the orbit, and then you put two transverse fingers above the zygomatic arch, and there you find the diphtherion. There you find the diphtherion. Now, what happens is that if you take a blow to the head in this region, it may happen that the bone breaks, which leads to a laceration of the middle meningeal artery. So maybe you don't see it from the outside, because what did we say?
That the lamina vitra interna maybe is more fragile than the external layer of the diploid. So it doesn't necessarily entail that there is a bone fragments that come out from the skull. But anyway... This blow to the side of the head, especially in this area, can lead to a fracture, not a fracture, sorry, a laceration of the middle meningeal artery.
And if laceration to the middle meningeal artery causes a condition that is called an extradural hematoma, okay? Extradural, meaning between the dura and the endosteum. because the meningeal vessel really lies almost embedded in the endosteum. And then there is the dura mater.
Now, there's something that I didn't make you notice, but I can use the same part of this image. Is there an epidural space here? Not really. In the spinal cord morning, we saw that in between the dura mater and the endosteum, vertebrae, there was a space with adipose tissues, there was a space, a real space.
But here in the scalp, the dura mater is really attached to the endosteum and therefore the meningeal vessels are squeezed literally between the endosteum and the dura mater. So the only moment in which a real epidural space forms is when something goes wrong because For example, if the middle meningeal artery breaks, blood starts to seep out and there the dura mater starts to detach from the endosteum, causing the condition that is called epidural hematoma, which doesn't mean it takes place immediately. Maybe the laceration is small and especially you don't notice it because there's not an actual visible fracture of the head, but in time, blood starts to pool.
in that area. Epidural hematoma to be distinguished by for example subarachnoidial hematoma. Here in a maybe a simpler drawing in blue or I think it now is in not in blue in pink is the dura mater and you see that is really attached to the endosteum but in the region where there has been a skull fracture of laceration of the middle meningeal artery. blood starts to pool in that area.
So the middle meningeal artery supplies the meninges, contributes to supply the bones of the skull and also forms some anastomosis with the cerebral vessels. Now, is there a lot of space in the skull? No. So blood starts to, you know, so you start to have an increase in the intracranial pressure.
That's why That's why when somebody takes a blow to the head, typically you try to monitor that person because maybe at the beginning, nothing. The person is conscious, everything goes fine, but then maybe there is a bleeding and it may take some time before the symptoms become evident. The increase in intracranial pressures causes a variety of symptoms, nausea, vomiting, seizure, bradycardia, and limb weakness.
It depends. Nausea and vomiting and bradycardia are typically signs of problems in the posterior cranial fossa in the brainstem. Okay, and then it depends.
And then here is just this tiny, tiny pharmacological note. You can treat it with diuretics, diuretics, so that you reduce the pressure. Otherwise, you really have to drill inside the skull and simply drain the blood.
Okay, I'm leaving you guys. And I'll see you. Do you have a lecture now? Yes.
What do you have? Thank you.