we'll continue with the muscles of the elbow joint and forearm and as we move down the arm you'll see that these muscles start to get smaller and also we start to find muscles under other muscles and then even some muscles under those muscles so we'll do the best we can with these two dimensional images but you'll really want to make use of the supplemental resources in this course to see the three-dimensional models or videos that are showing these muscles a little bit more realistically in the body so we'll start with muscles that move the elbow joint or you can say muscles that move the antebrachium meaning they're moving the forearm so even before we look at any of these muscles we should know all right if we're moving the elbow joint what we're saying is that the forearm will somehow change position so we're gonna be pulling on the forearm to make it move therefore all of the insertions must be somewhere down here and all of the origins must be somewhere up here maybe on the humerus but maybe even higher up than the humerus so hopefully that makes sense okay so let's start with this first group here all of these muscles contribute to elbow flexion what that means is they're all synergists they all are working together to perform the same action the biceps brachii is actually a two-headed muscle so you need to know that there's both a long head and a short head and the way that I remember this is if the cadaver or the person or the model or picture is in anatomical position long is always lateral long is lateral you might want to write that on a sticky note and put it on your phone for a week or something long is lateral it only works for the biceps brachii but it's still pretty handy so here is the long head here is the short head because this is lateral this is medial the origins are different for these two heads of the bicep brachii the long heads origin is on the glenoid cavity and the short heads origin is on the coracoid process of the scapula which you can just see peeking out here so these muscles have the same insertion and as we said the insertion must be somewhere down on the forearm because we're trying to move the forearm so in this case the biceps brachii insert on the radial tuberosity and contribute to elbow flexion now the synergists of the biceps brachii are the brachialis and brachioradialis so brachialis is the muscle it's fairly deep on the arm it's hidden mostly underneath other muscles we won't learn many details here we'll just say it's origin is somewhere on the humerus and it inserts on the ulnar tuberosity so that kind of makes sense right the biceps are inserting on the radial tuberosity and pulling on one side of the forearm so what's going to pull on the other side brachialis will pull on the ulnar tuberosity and finally we have the brachioradialis this is quite a large beefy muscle of your forearm its origin is somewhere on the humerus and it inserts somewhere on the radius keeping it pretty simple so just look at the name of that muscle brachioradialis basically means humerus radius that's its origin and insertion now let's look at the triceps which we'll call officially the triceps brachii the three headed muscle of the arm and there is a lateral head and a long head in a medial head what this means is that trick from the biceps where we said long is lateral at not gonna work here because there is both a long head and the lateral head and a medial head what typically works the best I think is two on the models is to find the medial head and that's kind of hidden on one side of this image but if you can find the medial head it's in the middle towards the middle of the body the lateral head is then very easy to find because it's the opposite direction and that just leaves the long head you'll have to kind of experiment with that on your own on different images and models the good thing about the triceps is that all three heads insert in the same place on the electrode on process of the ulna so remember that's your pointy as part of your elbow and they all have the same function they're all meant to extend the elbow so they're doing the opposite action of all the other muscles their origins differ the lateral head has its origin on the humerus along with the medial head it's only that special long head that has its origin all the way up on the scapula so a bunch of muscles and all we're talking about doing is just flexing and extending flexing and extending flexing and extending the elbow joint there is also one little lump of muscle down at your elbow called the and Konya s' okay now let's look at the muscles of the forearm so if you look at the anterior portion of your forearm mostly what you have in here are flexors we've already flex the elbow yeah but we can still flex the wrist and we can flex the hand and we can flex the fingers so we still need a lot more flexing muscles in our arm but you can see that here flexor flexor flexor flexor many of these muscles will you call flexors but the forearms can also pronate so one of the muscles involved in pronation is called the pronator teres it along with all of these other muscles will have the same origin the medial epicondyle of the humerus so look down at your body find your humerus remember where the epicondyles are and find the medial epicondyle you should be able to feel it sticking out from under your skin the insertion of pronator teres is on the radius and this is very tricky to show you on the video but here's my medial epicondyle this is a short muscle that crosses to the radius and when that muscle contracts by forearm pronates I think we'll do is jump from pronator carries to palmaris longus I always like to find this muscle first on any model or diagram because I can always find the palm region and then I just look for a muscle with a skinny tendon that's right in the middle of the anterior part of my forearm that's always gonna be palmaris longus palmaris longus has the same origin it inserts on the palmar aponeurosis which remember is a sheet like tendon and it can contribute to wrist flexion the thing about palmaris longus is that you might not even have it about 15% of people don't have palmaris longus some people will just have a skinny little tendon in there with no muscle attached so it doesn't really contribute anything in fact to the strength of flexion in your forearm I'll post more about that somewhere in canvas including a video so you can figure out how do you test to try to find the tendons in your wrist that will show you whether or not you have palmaris longus but whether you have it or not the models will have it the diagrams will have it and if you can find that muscle then you can easily find the next two muscles on our list flexor carpi radialis and flexor carpi ulnaris we should slow down and say okay so these muscles flex the cart B that means carpal wrist so both of these muscles contribute to wrist flexion one is on the radial side by the radius bone and want to sign the ulna side by the ulna bone so once I find palmaris longus I just look towards the thumb and I'll find flexor carpi radialis then I look towards the pinky and I find flexor carpi ulnaris now these muscles contribute to risk flexion but they also help you abduct and add duct the wrist if you think about their position and off to the side of the forearm that gives them a little bit of an ability to hug the wrist back and forth as well and finally where do these insert well they insert on the metacarpals remember our goal here is to move the hand so just like with many of these other muscles we've talked about if you're going to move something the muscle has to insert on the thing you're gonna move if I want to move my hand the muscles are gonna insert somewhere on my hand maybe on a palmar aponeurosis but more frequently or in this case we're talking about the muscles inserting on the metacarpals the hand bones not the wrist bone it's not the carpals but the metacarpals the last thing I'd like to be able to do after flexing my elbow at wrist is to flex my fingers yeah flex my fingers so flexor digitorum means flex your digits there's two muscles involved here though there's a superficial muscle called flexor digitorum superficialis and a deeper muscle flexor digitorum profundus so remember that if you make a profound statement like dude the Sun is like a star mom that's deep that's some deep thoughts right there so when we say profound what we mean is deep the superficial flexor digitorum and a deep hidden flexor digitorum called flexor digitorum profundus those muscles insert on the fingers because our goal is to flex the fingers we do have one more muscle in this region called flexor pollicis longus that allows you to flex your Pollux which is your thumb and if you find that muscle and follow it down you'll see the tendon goes all the way down to the thumb makes sense ok the last thing we need to do now that we've you know flexed our elbow and our wrist and our hand in fingers we need to be able to extend all that again so if you look on the posterior forearm you'll find a bunch of muscles and many of those are expenses let's look first at the origin of all of these muscles the lateral epicondyle of the humerus maybe it sounds familiar because on the previous slide all of these muscles had their origin on the medial epicondyle of the humerus great now when we're going to extend things we're gonna want to be able to extend wrist area as well as the fingers so let's start by extending the wrist extensor carpi means extend the wrist we'll want to extend the wrist on the radius bone side and on the ulna bone side so we have extensor carpi radialis and extensor carpi ulnaris but there are two muscles that will extend the wrist on the radius side there is a longus and brevis no worries they both have the same origin they both insert on the hand so that they can pull and extend the wrist and now they extend the wrist and they can abduct the wrist because they are on the radial side so they can hold the wrist back and they can hold courts of abduction the extensor carpi ulnaris as the same origin has the same insertion but because it's pulling from the opposite end of the arm it can extend the wrist and add duct the wrist so these are things you'll need to you know find these muscles on your own arm play around with some of these movements and make sure that it begins to make sense to you why they might be abducting or adducting extending or flexing and so on lastly we need to extend our digits we've got the same origin as before if we're going to move our digits we need to attach to the bones of our digits the phalanges to extend those fingers you can often look at a model or a diagram and find the tendons like on the digits here and follow those back to try to find or name the muscle so beneath all the muscles we just talked about are a bunch of other muscles that we won't learn any oh I ace for although I think you'll find it will be clear what these muscles do based on their name there is a special muscle that extends the the pinky called extensor Digital enemy if you see this muscle and you follow it down you'll see that the tendon leads to the pinky phalanges that's the extensor digit in the extensors of the mini tiny digit but you can also extend the thumb the Pollux and so we have a couple muscles that can extend the Pollux there is a long one in a short one extensor pollicis longus where you often just see the tendon and extensor pollicis brevis right next to it finally there's a separate muscle to help abduct the thumb the abductor pollicis long is just next to those other thumb muscles