 This is going to be a demonstration of another muscle of mastication, namely the masseter muscle. So this is the masseter muscle that we see in front of us. The masseter is the most powerful muscle of mastication. It originates from the electromagnetic arch and we can see the origin here. The fibers then descend down and as they descend down they twist slightly and they get inserted onto the masseter tuberosity on the lateral aspect of the angle of the mandible and this is the angle of the mandible. So this is the ramus of the mandible, this is the body of the mandible and this is the angle and there is the tuberosity here, it gets inserted there. The fibers of the masseter are very powerful and they were covered by a very thick, very strong and a very tough fascia which is referred to as the perotidomethetric fascia and part of that we have retained here. This perotidomethetric fascia not only covers the masseter muscle but it also covers the perotid gland which we can see here. In fact the perotid gland is closely related to the posterior aspect of the masseter muscle. That's why it is referred to as the perotidomethetric fascia and this perotidomethetric fascia also covers part of the sternocleidomastoid here and this is derived from the investing layer of deep cervical fascia. So we have completely removed that to show the masseter muscle. What is the action of the masseter muscle? The masseter is a very powerful elevator of the mandible. So that is the one which we use to crack hard substances with our molar teeth. When the masseter is contracting downwards, it exerts a tremendous pull on the zygomatic arch and that downward pull of the masseter is countered by this thick strong fascia which we can see here which is attached to the zygomatic arch from above. This is the deep temporal fascia. So the attachment of the deep temporal fascia from above gives a counter traction to the downward pull of the masseter to the zygomatic arch from below. The second action of masseter is especially the superficial fibers because the fibers as I said are twisting slightly. The superficial fibers are also responsible for protrusion of the mandible. So that is another accessory action of the masseter muscle. Coming to the nerve supply of the masseter muscle. The masseter is supplied by the massetric branch of the mandibular division of the trigeminal nerve which is C5V3. All the muscles of mastication are supplied by mandibular division of trigeminal nerve. The muscles of mastication are muscles of the first branchial arch or the first pharyngeal arch. So therefore the mandibular division is the nerve of the first branchial arch. So that is about the nerve supply of the masseter muscle. As I mentioned the masseter is attached to the lateral surface of the angle of the mandible on the masseter tuberosity. Correspondingly there is another muscle of mastication which is an intratemporal fascia on the inner surface that is the medial teregoid muscle. The medial teregoid muscle is attached to the teregoid tuberosity on the corresponding inner surface of the angle of the mandible. So therefore the masseter muscle which is a quadrangular shaped muscle on the outside and the medial teregoid muscle which is also a quadrangular shaped muscle on the inside they are mirror image muscles which split the angle of the mandible from outside and inside respectively. So in this connection there is an important clinical correlation. If a patient sustains a fracture of the angle of the mandible as traced by my finger here that fracture is self-splinted by these two mirror image muscles namely the masseter muscle on the outside and the medial teregoid muscle on the inside. The masseter as I mentioned forms anterior boundary, one of the anterior boundaries of the parotid gland. Not only that the parotid duct also runs on the surface of the masseter muscle and we can see that and in some patients as in this category there is some accessory parotid tissue which is referred to as social parotid disc which can also be present superficial to the masseter as we can see here. We have completely separated the parotid gland from the masseter muscle to show the deep surface of the parotid and we can see this important vein which is running behind the ramus of the mandible. This is the retro mandibular vein. We can also see this artery. This is the external parotid artery. Deep inside we can see this nerve here which I picked up. This is the facial nerve, the C7. So these are the structures which are located in the substance of the parotid gland and they constitute posterior relationships of the masseter. We have also separated the periosteum from this part of the bone to show you that this is the neck of the mandible. This is the head and the conical of the mandible which forms a temporal mandibular joint and the masseter is taking origin from the zygomatic arch just in front of the neck of the mandible. So these are some relationships of the masseter. Thank you very much for watching. If you have any questions or comments please put them in the comment section below. Dr. Sanjay Sanyal signing out. David O is our camera person. Have a nice day.