Osteology and Joints of the Forearm, Wrist, and Hand (Nursing)

00:01 All right. Now, let's continue our discussion of the upper limb by going to the elbow and we're going to start with where we left off last time with the humerus.

00:12 At the distal end of the humerus, we see that there are these bumps on either side called the lateral epicondyle and the medial epicondyle on the lateral, medial sides, respectively.

00:24 Epi means upon and there are these sideways projections of a condyle which is the round part that's actually going to articulate with the bones of the forearm but those portions are covered by articular cartilage because all ends of bones ideally at joints are going to be covered in cartilage so bone isn't rubbing up against other bone.

00:49 Distally in the elbow joint, we have two forearm bones.

00:54 On the lateral side, we have the radius and on the medial side we have the ulna.

01:00 And it's always good to remember when we talk about medial and lateral or really any anatomic terms, we imagine we're in the anatomic position with the upper limbs resting at our sides and our palms pointing forward so that way we have an idea in our mind which side is lateral, which side is medial.

01:19 Here, we see an x-ray of the elbow and we can make out the humerus because of how wide it gets out those epicondyles and then we can see the forearm bones with, again, the radius being lateral and the ulna being medial and one thing you'll notice is it looks very dense or very bright white at the very superior end of the ulna where it almost looks like it's overlapping with the humerus and that's what's actually happening.

01:48 We have to actually go to a lateral view though to see why it's overlapping.

01:53 And from a lateral point of view, we can see how the elbow is really a hinge joint because we have the humerus coming down meeting the radial head and then the ulna really cups it and it sort of provides this socket, if you will, for the rest of the humerus to fit nicely into and it's around this axis that will have our hinge-like movements. So here, we have an x-ray where we see it in a lateral position.

02:23 So, again, with the humerus coming down to the radius and ulna and we can see the ulna forms this cup-like structure so it can receive the humerus and that tells us a little bit about the movement that's going to happen at the elbow joint.

02:39 It's not going to have a whole lot of movement because it's constrained by this cup-like configuration and can really only move in two directions.

02:49 We can have a little bit of extension from a neutral position and then a lot of flexion, and of course the opposite of that will be going back to extension again.

03:00 So we really have flexion and extension and it acts, basically, as a hinge so it's a prototypical hinge joint.

03:09 If we look at the forearm a little bit more, it's quite a bit different from the arm because we have two bones here and there's going to be a lot of things that need to connect these two bones so they act in unison.

03:20 So, again, we have the ulna and we have the radius and going all the way in between is this connective tissue sheet called the interosseous ligament.

03:30 Interosseous just meaning between bones.

03:34 If we zoom in at the proximal end where it's near the elbow, there's a lot more.

03:40 We have a radial head that's going to be part of the articulation at the elbow joint and a neck separating that head from a bump or tuberosity on the radius called the radial tuberosity.

03:52 And when we have these bumps on the bone is because they serve as attachment points for muscles.

03:57 Similarly, that cup-like shape of the ulna has a posterior portion called the olecranon and then it's giving rise to a little notch called the trochlear notch.

04:09 Trochlea means pulley and then a coronoid process on the other side so that the distal end of the humerus is actually nicely wedged in between the olecranon and coronoid process.

04:22 And the ulna has its own bumps or tuberosities for muscles to attach to and they're called the ulnar tuberosity.

04:30 Between the two bones, we do have a proximal radioulnar joint.

04:36 And where there's a proximal joint, we can generally assume there's going to be a distal joint.

04:42 We do have a distal radioulnar joint as well.

04:45 At the distal end of these bones, you can see they're almost the opposite.

04:50 Proximally, the radial head was really small and the ulnar was really wide.

04:54 Distally, the radius become fairly wide and the ulna has a smaller head. It's almost like they're flipped.

05:02 And at the edges of both of these bones, we have little projections called styloid processes and they look like they're kind of reaching out and almost forming a cup-like shape here as well and that cup like shape is where we're going to find the first bones of our hand.

05:20 And when we're talking about the wrist and hand, the first thing we talk about proximally are those carpal bones that are wedged right up against the distal end of the radius and ulna and beyond those carpals are the metacarpals.

05:35 That's actually what meta means, next, so beyond the carpals, the next thing after the carpals are the metacarpals, the bones that make up the majority of your palm of your hand. And then, distally on the digits, we have the phalanges and the fingers or digits two, three, four, five have a proximal, middle, and distal but the thumb only has a proximal and a distal.

06:03 The movements at the wrist are similar to those of the elbow and that we have extension and we have flexion.

06:13 We also have movement in a little more degrees of movement than we do in the elbow and that's because if we think back to our anatomic position, with our palms pointing forward, this would be a posterior view of the right hand and we think, okay, the thumb in this sense is actually lateral to the pinky.

06:36 That way when we make a motion where our pinky is moving towards the midline, that would actually be adduction similar to the adduction of the arm that we saw at the shoulder joint, just on a smaller scale.

06:51 And if we move our thumb outward again, we actually will get abduction so it's a smaller scale movement but same ideas what we had at the shoulder joint.