In this video, we discuss more about the fourth pectoral muscle, serratus anterior. Not only does it help in stabilizing the scapula, it does a lot more.

Watch and enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this video, I’m going to be talking about the origin, insertion, and action of serratus anterior, the fourth of the pectoral muscles.

Let’s get right into it.

Here, you can see serratus anterior. As I mentioned in one of the previous videos, when we’re talking about serrations, if you’re dealing with a serrated knife, if you’re dealing with something that has a tooth-like or a saw-like appearance. That’s a convenient name for this muscle. If we look here, we can see those tooth-like projections like a knife, a blade of a knife that looks like this guy right over here.

This is serratus anterior and we need to know the origins, insertions, and the actions of that muscle. So, when it comes to the origin, you can see it a little more clearly in this picture over here.

The origins would be the external surface or the outside surface of ribs one through nine. You can see it here. Usually it’s one through eight. Sometimes, you see also on the ninth rib depending on the individual. But, in general, the the external surfaces of ribs one through eight or nine, and you can see that here.

But then, it wraps around posteriorly and connects right here on the, and this is the insertion point, the anterior surface of the medial border of the scapula. So, here’s the scapula, this is the left scapula just like we’re showing over here, and picture this muscle just going all the way posteriorly and then, extending all the way to the anterior surface of this medial border of the scapula.

Now, based on how that’s connecting, based on where it goes from the point of origination to the point of insertion, what is it going to do?

The first thing that it’s going to do is help to stabilize the scapula, so stabilizing the scapula basically by anchoring it on to the ribs. Then, when it contracts, if it contracts even more, what that’s going to do, is it’s going to cause the scapula to move towards the point of origination and cause protraction.

I wish this was 3D so I could show you the movement of the scapula. But, just picture the scapula moving along the direction of the serratus anterior. It’s moving the arm forward. It’s protracting the scapula.

But also, depending on how it contracts, it can move this portion even more and help with upward rotation. That one I can show a little better. Upward rotation of the scapula, that is also accomplished by serratus anterior.

So, in review. The name of the muscle is serratus anterior. You can turn off the volume to test yourself (I keep forgetting to say that). The point of origination would be the external surfaces of ribs one through eight or nine. Then, the point of insertion would be the anterior surface of the medial border of the scapula.

Its action, number one is stabilizing the scapula. It can also protract the scapula, and it helps with upward rotation of the scapula.

That’s pretty much it for this video. As usual, if you want more of this stuff, you know what to do. Head on over to the website, interactive-biology.com. You’re going to find more Biology videos there, some Biology games, and all kinds of resources to help make Biology fun.

This is Leslie Samuel. That’s it for this video and I’ll see you in the next one.