 This is going to be a demonstration of the layers of the scalp. So this is supine cadaver and we are showing the left side of the scalp. We have elevated the head up. So the first layer is the skin. The skin as you know is rich in hair follicles. It's got sebaceous glands and sweat glands. So therefore the skin can be afflicted by any of the conditions involving the hair follicles, namely folliculitis, sebaceous glands, namely sebaceous cyst and sweat glands. Closely adherent to the skin are these fibro structure that we see here. And we can see part of that on this layer also. This is the dense connective tissue layer. These small, tight, dense connective tissue fibres, they connect the skin tightly to the next layer. That is the aponeurosis. So therefore this dense connective tissue layer is layer number two. But it normally cannot be separated from the layer number three, that is the aponeurosis. However we have dissected it out. That brings me to the third layer. And the third layer is the one which we have reflected up now. This is the aponeurosis. This is also called the galia aponeurotica. In the middle portion it is aponeurotic. Antiretally we can see these muscle fibres here. These are the frontalis muscle. The frontalis muscle gets inserted onto the skin of the eyebrow. And it merges with the orbicularis oculi fibres. Pustially we have another muscle which you cannot see in this dissection is the occipitalis muscle. It takes origin from the superior nuclei and gets inserted onto the galia aponeurotica. So therefore when the occipitalis muscle contracts it tightens the galia aponeurotica and increases the functionality of the frontalis muscle which is responsible for producing horizontal wrinkles on the forehead. So this is about the middle portion of the scalp which is the aponeurotic. If we trace it further laterally it is no more galia aponeurotica. Instead it becomes this layer that we see here. This is referred to as the temporal parietal fascia or the anatomy textbooks call it the superficial temporal fascia. And this is the layer in which we have the neurovascular structures running and we can see that here. This is the superficial temporal artery, superficial temporal vein and the auricular temporal nerve. They run in this. Plastic surgeons call this SMAS, subcutaneous musculo aponeurotic structures of the face. And they use it for various reconstructive procedures. If we were to remove this layer which as I said is also called the superficial temporal fascia then we will reach the deep temporal fascia or the true temporal fascia which we have not decided out. So that is layer number three. Now once we reflect rail number three, my finger has gone into this plane here. This is the loose aorticial layer. This is also referred to as the danger layer of the scalp because of various reasons. Number one, this layer is poorly vascularized and therefore infection can very easily and rapidly spread in this layer. The second reason is emissary veins pass through this layer. These emissary veins can carry infection from the scalp to the intracranial venous sinuses. This is an M.R. venogram to show the intracranial venous sinuses which can get thrombose from infection from outside. Another reason is when there is a blunt trauma to the scalp, these emissary veins can rupture and they can produce extravastation of blood which can then track down like this. It cannot go to the sides because the superficial temporal fascia is attached to the zygomatic arch. It cannot go posteriorly because the occipitalis muscle is attached to the superior nuclear line. So therefore the blood tracks anteriorly and it circles the eye and produces what is known as black eye. Also called the racoon eye. This is a clinical picture to show periorbitelechemosis also called racoon eye and insect shows a resemblance to a racoon. These are the reasons why this layer is referred to as the danger layer of the scalp. And incidentally in the condition called avulsion of the scalp where the whole scalp namely the skin, dense connected tissue and the aponeurosis can be completely pulled off from the skull if the long hair gets trapped in a machinery. And that avulsion of the scalp also occurs through this layer that is the loose aerial tissue layer. That is layer number four which is also called the danger layer of the scalp. And then we have the next layer, it is layer number five and that is the one which we have picked up here. This is the periosteum or the pericranium which covers the calvarium or the vault of the skull. In this particular cadaver we see that they have done some surgical procedure here and we can see some pins and clips here. Periosteum gets attached to the sutural membrane between the sutures of the bone of the skull and from there it becomes continuous with the endosteum of the skull. This is also continuous through the foramen magnum with the endosteum or the periosteum on the inner surface of the skull and this also continues and becomes known as the periosteum of the base of the skull. The periosteum of the base of the skull is more densely adherent than the periosteum of the calvarium of the skull. Therefore, when there is a fracture of the base of the skull, the periosteum ruptures more easily and there can be leakage of CSF. So these are the five layers of the scalp namely skin, connective tissue, dense, upper neurosis, loose aerial tissue and periosteum. Thank you very much for watching. Dr. Sanjay Sanyal signing out. David, who is the camera person? If you have any questions or comments, please put them in the comment section below. Have a nice day.