Epicranial Group – Facial Muscles

00:01 All right. Our first muscle of facial expression is that of the occipitofrontalis.

00:09 This is actually a muscle that's comprised of two bellies.

00:13 The first belly here that we'll focus on is the frontal belly that you see highlighted in red.

00:19 And anytime we think about muscles, we have to think about their origin, their insertion, their innervation, and their action.

00:27 And the great thing about muscles of facial expression is that the facial nerve will be the nerve that innervates them.

00:35 But of course, the facial nerve has branches, and we'll highlight the specific branches that do innervate the muscles of facial expression.

00:45 First, is the origin of the frontal belly.

00:48 And that origin is from the epicranial aponeurosis.

00:52 The muscle... -- then we'll insert on the skin in the subcutaneous tissue of the eyebrows and the forehead.

01:02 It's specific facial nerve innervation is via the temporal branch.

01:08 And then lastly, the action of the frontal belly is to elevate the eyebrows and wrinkle of the skin of the forehead.

01:20 And this will produce a surprised look.

01:26 The occipital belly is shown and highlighted in red right in through here.

01:32 It works in conjunction with the frontal belly.

01:37 Its origin is the superior nuchal line of the skull.

01:43 It to have an attachment to the epicranial aponeurosis, and in this case, that is the insertion rather than the origin.

01:53 Its innervation specifically is the posterior auricular branch of the facial nerve.

02:01 And then lastly, the action of this muscle is to retract the scalp and this will increase the action of the frontal belly.

02:12 So it's synergistic.

02:14 Now, misspoke there.

02:16 This is really the last set of muscles of facial expression.

02:21 But really, what you're gonna see here these are really have no functional consequences in humans.

02:26 So the platysmal, in reality, is the last muscle facial expression of consequence.

02:32 So when we have these last set of muscles, the auricularis muscles, we have three sets of them.

02:40 There's the auricularis anterior as shown here.

02:44 We also have the auricularis superioris, that is shown right in through here, the middle of the three.

02:51 And then the last auricularis muscle is the posterior auricularis muscle.

02:57 And again, essentially nonfunctional in humans.