Humerus

00:01 So, now, let's turn our attention to the humerus.

00:04 This is the main single only bone that is situated within the arm.

00:09 And here, we can see the humerus extending down from the scapula towards the elbow joint.

00:14 So, it forms the shoulder joint and the elbow joint. It's the main bone within the arm.

00:21 So, here, we can see the humerus, here, we can see the scapula.

00:24 And where those two bones unite together, we have the glenohumeral joint.

00:29 It's a ball and socket joint.

00:31 Most distally, we can see the radius and we can see the ulnar and those together with the humerus form the elbow joint. So, let's just have a look at the humerus in a little bit more detail before we then go on to look at lots of the little bony prominences.

00:46 Here, we have the proximal end of the humerus and here, we have the shaft, and here, we have the distal end.

00:52 This is very much looking at the humerus, the right upper limb, looking at its anterior surface.

00:58 The proximal end forming the shoulder joint, the shaft running through the substance of the arm, and then, the distal end forming the elbow joint.

01:08 So, let's have a look at the humerus in isolation and if we look at that distal portion, we can see we have a very large rounded head of the humerus.

01:16 This articulates with the glenoid cavity. And then, directly lateral to that, we have an anatomical neck.

01:23 And that's one of two necks we have. We have the anatomical neck that runs just around the head.

01:28 And then, more towards the shaft of the humerus, we have the surgical neck.

01:33 And these are important landmarks as various different blood vessels will run across various different necks of the humerus.

01:39 So, bear that in mind for when we look at the blood supply later on.

01:43 Fractures in this region of the neck are extremely rare.

01:47 But some fractures around the surgical neck are more common and they could lead to very significant nerve damage which will ultimately lead to a loss of function within the upper limb. We can then see we have some tubercles.

02:01 These are just elevations, lumps, mounds, bumps on the surface of the humerus.

02:06 Here, we can see we have the greater tubercle. And here, we have the lesser tubercle.

02:11 Between those two, we can see we now have a sulcus or a groove, a depression.

02:17 And because it's between two tubercles, we call it the intertubercular sulcus.

02:22 Either side of that ridge as it extends down the shaft, we now have the crest on the greater tubercle and a crest on the lesser tubercle. And these are the elevations that lead up to those greater and lesser tubercles, creating that intertubercular sulcus. Why am I telling you these things? Because, again, they offer important sites for muscles to attach.

02:47 Now, let's move down and look at the shaft of the humerus.

02:50 Here, we can see as we're looking at the anterior aspect, we can see the anterior border of the humerus.

02:55 And then, we can see the lateral border which then, as it moves laterally and moves distally, becomes elevated as the lateral supracondylar ridge.

03:05 We can also see on the medial border, we have a medial supracondylar ridge as well and they will ultimately give rise to other bony prominences.

03:15 On the anterolateral surface and the anteromedial surface, we are offering more sites of bony attachment and they are running all the way down to the elbow.

03:25 If we turn it around and look at the posterior surface, we can see some other bony prominences.

03:30 We can see the deltoid tuberosity is on the anterior surface.

03:34 But you can also see that prominence peeking out on the posterior surface as well.

03:39 The deltoid tuberosity is where the deltoid muscle attaches.

03:44 We can also see on the posterior surface this radial groove.

03:47 And that's home to an important blood vessel and nerve. We'll come back to later on.

03:54 So, now, let's look at the distal end of the humerus. Here, we have these articular surfaces.

04:00 These are smooth surfaces that allow the joints of the elbow to actually function properly with both the ulnar and the radius.

04:09 The distal end of the humerus also does have non-articular parts. So, these bits won't articulate with the ulnar and radius but they form attachment sites for the capsule that surrounds the elbow joint.

04:22 So, on the distal end of the humerus, we can see we have some important bony structures.

04:28 We have the capitulum. This bit is most lateral on the humerus and articulates with the head of the radius.

04:35 So, here, we can see the capitulum articulating with the head of the radius.

04:40 Here, we can see on the more medial aspect of the distal end of the humerus, we have the trochlea and that's going to articulate with the trochlear notch of the ulna.

04:50 Here, we can see some very important functionality of the elbow.

04:55 We can see how if we go back to the capitulum and its articulation with the head of the radius, we can imagine because of the shape of the head of the radius, we have rotation of the radial joint of the radius there and that allows us to supinate and pronate our forearm.

05:11 If we compare that to the trochlea and the trochlear notch, that articulation really allows flexion and extension at the elbow joint which we'll be familiar with.

05:20 If we look at other bony features nearby, here, we have the medial epicondyle which is the expansion of the medial supracondyle ridge, and then, we'll also have a lateral epicondyle.

05:32 Again, the extension of that lateral supracondyle ridge.

05:36 These again, offer important bony landmarks for muscles to attach.

05:41 Here, we have the radial fossa and that allows the articulation with the coronoid fossa of other bony prominences so that when the elbow is fully flexed, those bone and articulations can nestle together within the elbow and help it to form a solid joint.

05:56 On the posterior aspect of the elbow, we can see the olecranon fossa.

06:00 And this is where the olecranon of the ulna will actually extend into during full extension of the elbow joint.

06:07 This is a deep depression and the olecranon of the ulna can be situated within this space.

06:14 The medial epicondyle on the medial aspect of the humerus is really quite a bony prominence.

06:20 You can feel that on yourself if you just run onto the medial aspect of your elbow.

06:25 An important nerve runs across this region and we'll cover that later on.

06:29 Here, we can see for some added detail now, the ulnar nerve passes through the posterior aspect of this groove.

06:36 It is a common site for injury.