 All right, in a previous video we had looked at the scapula and the clavicle, and so today actually we're going to look at the bones of the, basically the arm. And these are going to be the humerus, the ulna, the radius, the carpal bones, metacarpals, and then the flanges, and then another video will show you the, basically the lower extremities. But we'll start off with the humerus, and if you look at the humerus, a few things that you'll notice, once again make sure that you understand your directional terms, because there are going to be certain features at the superior side, and the inferior side, as well as the anterior and posterior side that we'll be looking at. The humerus, at one end it has this kind of roundish end called the head of the humerus, and it's basically attached to a very, to a neck, so any time you have a head you have a neck, and you'll see this particularly if you want to orient it properly, you'll notice that the head of the humerus is always going to be facing medially, which tends to make sense because the glenoid cavity of the scapula is going to be facing laterally. So the head of the humerus in particular is part of the ball and socket joint called the shoulder joint. Also at the superior side, just past the head of the humerus is the greater and the lesser tubercles, and these are basically attachment points for muscles. On the shaft region or the diaphysis you have this roughened area called the deltoid tuberosity, and you can kind of feel it if you pick up a bone, and this is actually an attachment point for a muscle called the deltoid. At the inferior side, if you look at just the anterior inferior side, you'll notice several processes. On the lateral side you have the capitulum, and a small process here called the lateral epicondyle. These are both attachment points for muscles. On the medial side you have the trochlea, notice it kind of looks like a pulley. If you've seen a pulley it kind of has this little spool-like structure and some, basically some thread that you can kind of use to lift very heavy things. Also on the medial side you have this medial epicondyle, and this one is actually very prominent. If you really kind of feel on either side of your elbow, you'll notice there's two prominences, and the bigger one is this medial epicondyle. The trochlea of the humerus is going to fit in with another feature on another bone called the ulna, and the feature that fits into is the trochlear notch, and you'll notice that basically the trochlear notch of the ulna is rotating around the trochlea of the humerus, and so this is actually one of the articulation points of that elbow joint. Now on the posterior inferior side of the humerus you'll notice this deep depression here. This is called the alecronon fossa, and the alecronon fossa is going to be where a feature once again on the ulna called the alecronon fits into, and this alecronon on the ulna is actually the point of your elbow, which obviously you can easily feel. And so, you know, these two features, the trochlea and then the alecronon fossa, are part of that elbow joint. Now looking at the lower part of the arm, we essentially have two bones. We have the ulna, and then we have on the medial side, and then we have the radius on basically the lateral side. And this is medial and lateral when essentially you hold your arms in anatomical position. So if you were to, the radius would always be here along your thumb side where the ulna would be here along basically your pinky side. Looking at the ulna for a second, some features that you see of this that have already been previously pointed out is the alecronon, once again that's the point of your elbow. The trochlear notch, which always reminds me I think of some of those nature programs where the snake is being milked for poison, that kind of always reminds me of that. But the trochlear notch, which is rotating around the trochlea, so the ulna does articulate with the humerus, it also you'll notice articulates with the radius. It's a little hard to see, but you can see that there's a point right here on the proximal end where the ulna and the radius would actually rotate around each other, which would allow us to basically rotate our forearm here. Looking at the radius, two points to note is that it has a very flat head that will easily help you to distinguish it from the ulna. The other feature point is the radial tuberosity, which you can kind of see right there, it's just this process below the radial head, and this is an attachment point for an important muscle in your arm called the biceps brachii. Kind of continuing down the arm, we've got the carpal bones, and you'll notice that there are eight carpal bones, now three of these, one, two, three, are going to articulate basically with the radius and the ulna, and then the others are going to articulate with the bones of your hands, which are called the metacarpals. Now they each do have individual names, but for the purposes of this video and for the class, you just need to know them as a group rather than the individual names. So just recognize these as carpal bones, you'll notice that they're sort of cube shape, they are considered short bones because they don't have these well-defined ends in shaft regions. Looking in the hand, you'll notice that the metacarpals, and there are actually five metacarpals per hand corresponding to basically your five fingers, because each metacarpal you'll notice is attached to a bone associated with your finger. We start counting the metacarpals based on which one is associated with the thumb. Well, how do you know which one's associated with the thumb? Well, that's where you have to look at the bones in the digits themselves. These in the digits are called phalanges, and notice that each finger has three phalanges, but the thumb has two. So if you can recognize the digit that has two phalanges, then you know where to start counting, and then it becomes easy. It's just metacarpal one, metacarpal two, metacarpal three, metacarpal four, metacarpal five. Traditionally, these have been written as Roman numerals. And if you look at the bones of the digits, you've got your phalanges. Singular version of this is phalanx. With the thumb, you have a proximal phalanges, and then a distal phalanx. Now with the fingers, then you have just proximal, middle, and distal phalanges associated with each of the fingers. And so that actually completes the discussion of the bones of the arm.