Are YOU Missing a Muscle??? | Here’s a Test to Find Out!!

… but it also flares into the palm, orthis palmar aponeurosis — which I'm going to zoom in for you — that you can seein the palmar surface of the hand here. Some of you are losing muscles! And I'm not talking about because you'resitting on your Gluteus Maximus all day long, watching amazing anatomy videos on YouTube. I'm talking about that youwere never even born with them! There are a handful of muscles in the humanbody that are variable from person to person because these are thought tobe evolving out of humans. We need to talk about why that is, .

And we're gonna even talk about a little test youcan do to see if you've got one in your forearm. And don't worry — if you don't have this muscle, you can just tell your friends that do thatyou're a little bit more evolved than them. So let's do this! As I already mentioned, there area handful of muscles in the human body that are variable from person to person. And we're going to focus on this one in theforearm because you can actually figure out if you have this just sitting here watching thisvideo with a little test that we'll show you. The other ones, you're gonna have to dosome sort of imaging study to find out .

If you have those, and that's justnot really feasible for most of us. But to understand how this works withthis forearm, let's take a look at the upper limb dissection to get some contextaround the muscles of the upper limb. So here is a dissection of the upper limb. Just FYI you guys — people get a littlebit uncomfortable with fingertips and the skin of the fingertips, so we've just covered that for your viewing pleasure — or yourviewing comfort, I guess I should say. But let me move the upper limbso you can orient yourselves. It's essentially just like myupper limb is sitting like so. .

Now this is the brachium, or the upper arm, which there are 4 total muscles herein the brachium, or the upper arm. Now if I move down here and grab the forearm— which the fancy-pants name for forearm in anatomy is the antebrachium— there are 20 muscles here. So 4-20. Some of you remember 420 forcertain extracurricular activities. I remember 420 because of itsreference to anatomical awesomeness. So regardless of how you want toremember the reference of 420, let's just go a little bit further. .

So again, 4 muscles here, 20 muscles here. But there are 11 more inside the hand. And if we take a step back and kind of thinkof that logic — the muscles of the brachium, or the upper arm, are going to mobilize the elbow. And what does the elbow do? We're like flexion, extension, and we're kind ofdone with also some supination, and that's it. But when we get to the forearmmuscles and the hand muscles, we're doing all sorts of things like,you know, abduction and adduction. Waving, things like this… wigglingthose fingers… doing “the Spock”… .

You know, opposition — things of that nature. Lots of specialized work here. So again, it would make sense to have more muscles for more, you know, fine motor movements thatwe're going to do with the wrist and the hand. Now 20 muscles here, right? Some of you only have 19…. And finally, we can talk aboutthis mystery variable muscle here. So let's take a look here atthe cadaver again, and here is this mystery muscle, called the Palmaris Longus. .

Now you can see why I got the name Longus,because it's a fairly long tendon here. There is a Palmaris Brevis, FYI. But it also flares into the palm, or thisPalmar Aponeurosis — which I'm going to zoom in for you — that you can see inthe palmar surface of the hand here. Now again, this muscle coming all theway back to the elbow is not a very big muscle here — just a small little musclebelly, so not a very powerful muscle. But what does it do? This Palmaris Longus musclecan weakly help flex the wrist. I say weakly, because there are othermuscles that are much more powerful .

And stronger with flexing the wrist. Now because it goes to the palm of the hand andthat Palmar Aponeurosis, when you do certain gripping motions it can put tension on the skinand the connective tissues of the palm to kind of help create that cup in the palm of yourhand that you're seeing here with gripping. So this always comes back to this question of, “why do some people have this muscleand others not have the muscle?” And those who don't have these variable musclesthat we've mentioned, don't really miss them. And what I mean by that isthat they're not necessary for day to day functions or physical activities. .

For this muscle in particular — rememberwe had 11 other muscles in the hand and all these other forearm musclesthat could perform similar functions. So if you don't have this muscle, youcan still do all the hand and wrist movements that you would need to do evenwithout the small little Palmaris Longus. And of course, this knockson the door of evolution. And to give this brief overview — orthis idea of how this works — is animals, over the “bazillions” of years of developmentand evolution and things of that nature, they were exposed to certain environmentalfactors and participated in certain activities, and a combination of all these variablesactivated and turned on certain genes. .

And as those genes were more active andmore frequently turned on and expressed, those genes were more likely to bepassed on to offspring in generations. And as things got more specialized, some muscles took over other functionsand rendered other muscles less useful. And that's the idea of this muscle kind of evolving out of humans,as well as the other muscles. And just one quick little thing I need to mentionbefore I show you the test to see if you have this muscle — Justin and I have been posting on TikTok,Instagram and YouTube for a little while now, and we've noticed there are sometrigger words or trigger topics .

That get people really firedup in the comments section. Evolution tends to be one of those, you know? So whether you believe in evolution,or have some religious convictions, or a combination of the two — go ahead anddiscuss, but just be nice to each other. It's not that hard! It's — you know, the Institute of HumanAnatomy comment section is a safe space, okay? And I'll even start — I believe in evolution— obviously, because I'm teaching about this. I think the evidence is pretty strong. However, I grew up in a strongly religiousfamily, and i don't necessarily think they .

Have to go against each other —they can coexist, in my opinion. Let me know what you think below. So finally, we get to test ifyou've got this muscle or not. To do this, I must de-glove. Okay! So what you're going to do, is you'regoing to slightly flex your wrist. You don't want to crank this thing all the way up. You just want to slightly give it some flexion, and that's not going to giveyou everything you need. .

What you need to do, is slightly flex the wrist, and then pinch your pinky and yourthumb together pretty tightly. And you can see that difference of that tendonthat starts to bulge out of my skin there. Now don't get confused by the secondarytendon that's next door to it, as you can see there's two tendons here,but it's the one that's bulging out more. The one that's closer to the thumb is actually this other muscle righthere called the Flexor Carpi Radialis. If you want to get more informationon that, Justin just did a Carpal Tunnel video on it, so fun there. .

But again, take a look at how that works. But I need to show you — my other side. So if you take a look here, I do not have it on myleft wrist or left forearm — it's missing there. I just have that other tendon,that Flexor Carpi Radialis tendon, but I'm missing the Palmaris Longus. And a lot of you will see that you'llhave it on one side versus the other… you may have it on both sides…or you may not have it at all! And again, like I mentionedat the beginning of the video, if somebody tries to make fun of youfor not having a Palmaris Longus, .

Your rebuttal is that you are a littlebit more highly evolved than them. My left side's a little confused comparedto my right side — it wanted to evolve faster than my right side, I guess… who knows? And one cool thing, from a clinical perspective. For those who have this tendon you could use it for a graft if you had someinjury to a certain ligament. For example, pitchers will sometimes injure —pitchers like baseball pitchers — will sometimes injure this ligament calledthe Ulnar Collateral Ligament. And to help repair this ligament, you couldtake this tendon from the Palmaris Longus .

And use it as a graft torepair this damaged ligament. So this wimpy little muscle can be usedfor, you know, showing people cool tricks. But at the end of the day — eh… As always, thanks for watchingand going on this tour of the upper limb and the Palmaris Longus with us. Please like, subscribe, ring the bellso you know when we drop new videos. We love the comments everybody— please blow that section up. We have our affiliates down below — welove and appreciate all of your support. And have fun testing your PalmarisLongus with your friends and family. .

I don't know what that was…like spirit fingers… it has nothing to do with Palmaris Longus… okay bye!
Are YOU Missing a Muscle??? | Here’s a Test to Find Out!! ____ In this video, Jonathan from the Institute of Human Anatomy discusses the variability of certain muscles in humans, and even shows how you can test yourself to see if you’re missing a muscle in your arm. ____ New digital coloring book designed using images of real cadavers is now available in our merch shelf!! ____ Want to Get a Personalized Video Response to a Question? Ask Us Here! ____ Affiliate Links: mUvmethod Coupon Code for 30% OFF: IOHASPLITS30 Codex Anatomicus Coupon Code for 20% OFF: IOHA20 ____ Connect with us on social! TikTok: Instagram: Facebook: LinkedIn: Website: ____ Audio Credit: T-Rex/Bird Photo Credit: Zina Deretsky, National Science Foundation ____ #Muscles #MissingMuscles #InstituteOfHumanAnatomy