In this episode, we review the muscles, innervation and functions of the muscles of the anterior forearm which I previously covered in the last two Anatomy videos. Use this to aid you in studying for these muscles. But, it’s best if you can also watch the previous two.
Transcript of Today’s Episode
Hello and welcome to Interactive Biology TV where we’re making Biology fun. My name is Leslie Samuel. This video is brought to you by our partners over at 3D4Medical.com, the creator of this Anatomy app and a number of Anatomy apps like this.
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In this video, I’m going to be giving a review of the anterior forearm. More specifically, I’m going to talk about the muscles of the anterior forearm then, I’m going to talk about the innervation to those muscles. Lastly, the general functions of those muscles of the anterior forearm.
Let’s get right into it.
I am going to zoom in to the anterior forearm region There are a number of structures that I just don’t really need so, I’m going to hide some of the muscles. I am for now, going to get rid of the arteries and some of the cutaneous nerves.
All right so, first I’m going to deal with as I mentioned, the muscles of the anterior compartment. If you remember from one of the previous videos, there’s a superficial compartment and there’s a deep compartment of the anterior forearm. We’re going to deal with the superficial ones first. We’ll review those first.
Now, if you remember, for the superficial ones, we start with the P.F.P.F. What is that?
First, we’re going to start with the pronator teres muscle. That’s the first P. Then, we have our flexor carpi radialis. That’s the first F. Then, we have the next P which is our palmaris longus. Then, we have the next F which is our flexor carpi ulnaris. Those are the first four, P.F.P.F. — pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris.
Then, if you remember correctly, beneath those first four muscles, I’m going to remove some of those muscles, we have the fifth muscle or the last muscle of the anterior compartment, the superficial compartment of the anterior forearm, that is our flexor digitorum superficialis, that’s beneath the first four. This is the one with the split tendon, so you can see those split tendons going to the individual digits.
That’s the first five muscles of the superficial compartment. In some references, you might see this flexor digitorum superficialis called an intermediate layer instead of a superficial layer. Either way is fine. Those are the first five muscles.
Let’s hide this superficialis here and then, we’re going to look at our deep compartment. In the deep compartment, we have three muscles. Those three muscles are, the first one is the largest, that is your flexor digitorum profundus. Once again, you see this digitorum muscles has this split tendon. You can see those four split tendons going to the individual digits. That’s our flexor digitorum profundus.
Then, we have our flexor pollicis longus. “Pollicis” refers to the thumb. You see that one going down and inserting on the thumb. That is your flexor pollicis longus. Then, we’re going to hide this two so that, we can see the last of the anterior muscles. That is our pronator quadratus, that short quadrangular-shaped muscle that’s going down from your ulna to your radius laterally, that is your pronator quadratus muscle.
The Innervation to the Muscles
Those are all of the muscles and now, we’re going to talk about the innervation to those muscles. All right, so what I’m going to do is I’m actually going to hide the biceps. It looks like one is missing so, what I’m going to do is I’m going to refresh this and then, I’m going to hide some of these muscles. I’m going to get rid of my cutaneous nerve once again and there we can see it very clearly. Add back a layer of muscles just to make things interesting.
All right, so the first muscle, the first nerve that’s going to be innervating most of these muscles, six and a half of the eight muscles is going to be this nerve that comes along here via the cubital fossa. That nerve that you see here and I’m going to just outline it so you could see it more clearly. That is your median nerve.
That median nerve is going to get most of the muscles, six and a half of the eight muscles. Now, I’m not going to tell you what the six and a half are. Why?
Because it’s much easier to remember the one and a half muscles that don’t get that nerve. And, if you know that one and a half muscle, then, all of the rest you just know that that’s going to be getting innervation from, generally speaking, this median nerve.
So, what are the exceptions?
The exceptions are going to be one and a half muscles that get innervated by this nerve right here and that is your ulnar nerve. The one that I just showed you just now is your ulnar nerve. That’s the one that goes there behind the medial epicondyle. It’s your funny bone. That thing, when you hit it, you feel that shocking sensation going all the way down your forearm. That is your funny bone, that is the ulnar nerve.
That ulnar nerve is going to get one full muscle and that full muscle, really easy to remember because of the name, that is going to be your flexor carpi ulnaris muscle. The flexor carpi ulnaris gets innervated by the ulnar nerve. It makes sense.
The last one, half of it is going to get innervated. Let’s hide some of these. Let’s hide the flexor digitorum superficialis and our palmaris longus and then, we have our flexor digitorum profundus.
That flexor digitorum profundus, a relatively wide muscle, half of it, the medial half is going to get innervated by the ulnar nerve. So, this half, ulnar nerve and then, this half, median nerve. It makes sense because you have the median nerve coming down here.
The Function of the Muscles
All right so, that is the innervation of these muscles. Lastly, I want to generally speak about the function of these muscles. The anterior compartment, for the most part, it’s going to function in flexion, either flexion of the wrist, flexion of the fingers, it’s going to function in flexion.
However, you have two that are going to function in pronation of the hand and those should be, no surprise to you, the first one is going to be your pronator teres and the last is going to be, I’m not going to hide the muscles. I’m just going to show the pronator quadratus. So, the two with “pronator” in the name, those are the ones that are going to function in pronation of the forearm. All of the other muscles, going to function in flexion — either flexion of the wrist, the digits, for example the flexor digitorum muscles, that’s going to function in flexion.
That’s pretty much it for this video. So, in review, we’ve looked at the muscles of the anterior compartment. I spoke about the innervation of those muscles to the anterior compartment and lastly, I spoke about the function of those muscles in the anterior compartment. If you found value in this video, feel free to share it. Like it and all that good stuff.
And, of course, if you want more details specifically for this episode, come back to the blog at Interactive-Biology.com/107. This is video number 107 so, you can get more detail about the origins, and the insertions, and the innervation and the action and the function of all of these muscles.
Of course, you can just visit the website, generally speaking at interactive-biology.com for more resources to help make Biology.
This is Leslie Samuel from Interactive Biology TV. That’s it for this episode.[table “” not found /]
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