Muscles of Mastication

00:01 The next group of muscles we're going to look at are called the muscles of mastication.

00:06 Mastication just means chewing.

00:07 So these are the muscles that help us chew our food.

00:11 We're gonna look at a lateral view and a posterior view in order to see all four muscles of mastication.

00:17 From the lateral view, we can see a very large broad muscle in the area of the temporal fossa called the temporalis.

00:26 More laterally, we see coming down from the zygomatic arch to the angle of the mandible, we have the masseter.

00:34 And then more internally, from this posterior view, we could see the medial and lateral pterygoid muscles.

00:42 So let's take a look at the temporalis.

00:45 So here we see, it's attaching to the bones of that temporal fossa, which is how it got its name.

00:52 And it's coming down and attaching to the coronoid process of the mandible, which is one of those two projections of the ramus of the mandible.

01:00 In terms of function, the temporalis is a very big muscle that helps elevate the mandible, which is really helping us in the act of chewing by bringing the teeth together.

01:12 It also helps with posterior movement of the mandible or retraction.

01:19 The next one, the masseter.

01:23 Attaches to the zygomatic arch, which again is a combination of zygomatic and temporal bone.

01:31 And then coming down to the ramus of the mandible, kind of near the angle.

01:37 In terms of function, this is also going to help elevate the mandible.

01:41 And again, that's because chewing requires the most force in bringing teeth together.

01:46 That's why we have these two really strong muscles acting with elevation of the mandible.

01:52 If we fade out the bone of the mandible, we can see the medial pterygoid because it's going to be medial to the mandible and we won't be able to see it otherwise.

02:02 So its attachments are on the tuberosity of the maxilla at least for its superficial head and the medial surface of the lateral plate of the pterygoid process.

02:15 That's going to be the deep head.

02:18 And they're going to attach to the ramus of the mandible, again, close to where the angle is.

02:24 Keeping in mind it's on the medial surface of the mandible.

02:28 In terms of function, the medial pterygoid also help with elevation of the mandible.

02:34 But they also, in conjunction with the lateral pterygoid help with side to side movement of the jaw.

02:42 We swing around to a posterior point of view, so we had look more medially or internally, we can find the lateral pterygoid muscle.

02:51 The lateral pterygoid has an upper and lower head and we see that the upper head is sitting here in the roof of the infratemporal fossa.

03:01 The lower head is going to attach to the lateral surface of the lateral plate of the pterygoid process.

03:09 Again the medial pterygoid attached to the lateral plate as well but on its medial surface.

03:16 And this head is going to attach to the capsule of the temporal mandibular joint, which is on the consular process of the ramus of the mandible.

03:27 In terms of function, the lateral pterygoid due to the orientation of its fibers can actually draw the jaw forward or cause protrusion.

03:37 And like the medial pterygoids can help with side to side movement of the jaw.

03:42 It's also the only one that can actually depress the mandible.

03:47 We only need one muscle to do that because generally lowering the mandible can be achieved just by relaxing the other muscles and letting gravity do its work.

03:58 In terms of innervation of the muscles of mastication, it comes from branches of the mandibular nerve or trigeminal nerve (V3).