 Some important sitting points about the layers of the scalp. We have reflected the scalp on the right side of the skull. This thing that we see here is the skin. The skin is thicker than normal, it's got plenty of hair as we know. Therefore, hair related infections of the scalp are very common. We can have sebaceous cysts, we can have folliculitis, and all sorts of infection of the scalp because of the hair follicles. One very common condition is called alopecia. There are hundreds of causes of alopecia. One particular cause which we have seen in hospital practice is called traction alopecia. That is seen in nurses. When they tie their hair tightly back and it produces traction and the hair comes off on the sides of the skull. That is called traction alopecia. This skin was densely adhering to this underlying structure by the remnants of this tissue that we can see here. This is the dense connective tissue layer. The dense connective tissue layer has got multiple short, tough strands of fibrous tissue which connect the skin to the underlying aponeurosis. This dense connective tissue layer and the aponeurosis together forms layers 1, 2 and 3. And this is referred to as scalp proper. Squamous cell carcinoma, basal cell carcinoma, melanoma of the scalp is quite uncommon. And when we remove such a tumor, we have to do a rotation flap to cover the defect. And we use all these three layers together, namely the skin, the dense connective tissue and the aponeurosis and we cover it. And the bare portion is then covered by a split skin graft. Blood vessels, the arteries they ramify through this dense connective tissue layer. Whenever there is any injury of the scalp, these blood vessels cannot contract and retract and therefore they continue to bleed. And that is one of the reasons why scalp injuries bleed so profusely. The other reason being, these arteries form extensive anastomosis with each other and with the opposite side. If the long hair gets caught in a machinery, then these three layers can get averse from the loose area tissue layer as a composite unit. And that is referred to as aversion of the scalp. In the mid-19th century, the Native Americans used to scalp their enemies as a trophy and they used to scalp it through this layer. Therefore, this layer is also referred to as the danger layer of the scalp. This is the loose area tissue layer. Apart from the fact that we mentioned about scalping and about the aversion, this is the layer which contains the emissary veins. So, therefore, infection can travel through the emissary veins and produce intra-angel sinus thrombosis. Because this is poorly vascularized, infection can also spread very rapidly in this layer. That is also another reason why it is called the danger layer. And finally, last but definitely not least, these emissary veins can rupture in blood trauma to the head and the blood can then track under, and this is the anterior part of the aponeurosis and it can track under the aponeurosis and the muscle and it can come around the eye as black eye or racoon eye. These are some of the reasons why this loose area tissue layer is also referred to as the danger layer of the scalp. That brings me to a few important points about this aponeurotic layer itself. The middle is the aponeurosis, also referred as the glia aponeurotica. So, we have cut the aponeurotic layer in the middle to show this is the posterior part and this is the anterior part. Posteriorly, it continues as the occipitalis muscle and my finger is stopping here because it is attached to the superior-neocal line. Anteriorly, you can see this muscle here. If you watch very closely, this is the frontalis muscle. Oxypitalis muscle is inserted onto the glia aponeurotica. Frontalis muscle takes origin from the glia aponeurotica and this frontalis then gets inserted onto the skin, subcutaneous tissue of the forehead and the eyebrow. So, when the occipitalis muscle contracts, it makes the glia taut and it increases the functionality of the frontalis muscle. So, when the frontalis muscle contracts, it produces horizontal wrinkles of the forehead. If we were to trace the glia aponeurotica laterally and I have done that, we can see that there is a distinct difference in the texture. Closer to the midline, it is thick and more laterally, it is much more thin and this is the other part of it. Posteriorly, we can see it is quite thick here and laterally, it is much thinner. This lateral portion is not the glia. Instead, it is referred to as the superficial temporal fascia. In anatomy textbooks, in surgical textbooks, this lateral extension is referred to as temporal parietal fascia. This temporal parietal fascia is a superficial layer above the main temporal fascia which continues laterally and it gets attached to the zygomatic arch here. And incidentally, this is one of the reasons why any blood which is tracking in this layer lose the cellular tissue layer cannot move laterally because this is attached to the zygomatic arch and that is the reason why it moves only forward. Running in this superficial temporal fascia or the temporal parietal fascia, we have these gut vessels and we can see some of them here. These are branches and tributaries of the superficial temporal artery and the superficial temporal vein. This superficial layer or the temporal parietal fascia is used by plastic surgeons for various reconstructive procedures and therefore, it is also referred to as the superficial musculo-aponeurotic structures of the head and face. So that is about this superficial layer of the temporalis fascia which is the lateral extension of the glia aponeurotica. And finally, coming to the periosteal layer, we can see this is the periosteal layer. It is also referred to as the pericranium. The periosteal layer is continuous with the sutural membrane in the sutures between the bones and it continues onto the inner surface of the skull as the endosteum. If this periosteal layer is removed, is abolished from the skull bone, then that portion of the outer table of the skull will undergo necrosis and that is known as sequestrum formation. So if there is any removal of this periosteum, then we have to let the diplo form a granulation tissue. Only then we can put a skin graft because a bone without periosteum will never take a graft. So this is some of the clinical applications of the scalp layers and the various functional uses of the scalp. Incidentally, we also noticed that this patient had a fracture of the skull and they were attached by means of these clips here and they had inserted a ventricular peritoneal shunt and we can see the ventricular end of the shunt here. We can see the reservoir here, we can see the valve here and we can see the distal end of the shunt coming down here and we can trace the rest of the shunt to the peritoneal cavity. So these are some of the salient points which I wanted to mention about this cadaver and all the layers of the scalp. Thank you very much for watching. Dr. Sanjay Sanyal signing out. Anderson is our camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day.