Humerus – Bones and Surface Anatomy of Upper Limb

00:01 Now let's move to the humerus. This long bone that sits within the arm of the upper limb. It attaches proximally via the head of the humerus to the scapula and articulates distally at the elbow joint with the ulna and the radius. So here we can see both an anterior and posterior view on the slide. Let's look at this in more detail. So this is the anterior view of a right humerus. So here we have got the head of the humerus that will be articulating with the glenoid cavity. So the scapula will be positioned here and this is the lateral aspect of the humerus. We can see down here we have a structure called the lateral epicondyle. We will come back to that later on. I just really want to concentrate on this proximal region of the humerus up here towards the head of the humerus. And we can see that we have got this head here that is going to articulate within the glenoid cavity to form the glenohumeral joint. And you will see that the glenohumeral joint is a really mobile joint. We will come back to this when we look at the joint itself and the ligaments that help to hold in more detail later on. But we can see that the glenoid cavity is very shallow. It is not a cup like which has the head sitting into it. The glenoid cavity is very shallow and the head of the humerus sits alongside it. And due to this shallow glenoid cavity, the upper limb is very mobile.

01:31 So we can all move our arm way above our head and that holds that movement, it holds itself to the articulation between the head of the humerus and the glenoid cavity.

01:41 The humerus has a neck, in fact it has two necks. One neck is known as the anatomical neck and the anatomical neck sits just behind the head of the humerus. It is an important attachment site for the joint capsule of the glenohumeral joint. We can see the head here and then this dotted line is indicating the anatomical neck. The anatomical neck is positioned between these two important bulges of bone, these are known as tubercles. And the tubercles sit distal to the anatomical neck. So the anatomical neck is positioned between the head and these two tubercles. The second neck I want to talk about is the surgical neck and that runs around the humerus, below or inferior to these two tubercles.

02:36 Let's concentrate on the tubercles for a moment. We have the greater and the lesser tubercles.

02:41 And these are important in offering sites for muscles to attach. So importantly the rotator cuff muscles attach to the greater and the lesser tubercles. And these two tubercles are separated by a groove which we can see here and this is known as the intertubercular sulcus or the intertubercular groove and it runs between the two tubercles and later on we'll appreciate the various muscles attach in this groove or this sulcus and it also contains the tendon of the long head of biceps brachii that runs up in this direction here.

03:23 We'll come back to that later on. Now let's move down on this anterior surface to the shaft of the humerus. We can continue down here with the lesser tubercle as the crest of the lesser tubercle and another crest coming down from the great tubercle here. And we can see this in more detail if we look at specifically the shaft of the humerus. We have these two crests coming from the greater and lesser tubercles still forming this intertubercular sulcus down onto the shaft of the humerus. And we can see that on this more distal aspect of the humerus. We can see as it tapers away moves distally towards the elbow joint, we have what are known as medial and lateral supracondylar ridges. These medial and lateral supracondylar ridges are ridges formed as the humerus begins to dilate distally.

04:20 So as the humerus passes towards the elbow joint, it begins to dilate. And these ridges are forming that dilation which eventually leads on to the lateral and medial epicondyles.

04:33 So we can see the medial and the lateral supracondylar ridges here.

04:39 We can also see, we have on the lateral aspect again we have got the head here so this is the medial aspect. On the lateral aspect we have a groove here and that is known as the deltoid tuberosity and that's the attachment site for the deltoid muscle. So deltoid muscle attaches to the deltoid tuberosity we can see here. Most distally the humerus dilates into two condyles of the humerus and these form the articular surfaces that articulate with the radius and ulna and these articulations form the elbow joint. There is two articular surfaces. We have the trochlea we can see here medially and we have the capitulum laterally.

05:27 And these are important for articulating with the radius. So the radius is going to articulate with the capitulam and the ulna is going to articulate with the trochlea of the humerus.

05:37 So these form two important articulation sites. We can also see just before these condyles we have these little depressions called the radial fossae and the coronoid fossa.

05:50 And these little depressions allow these radius and ulna bones to sit in these little depressions when we fully flex our elbow so they can accommodate, as we'll see when we cover the elbow joint. They can cover the bony structures on the ulna and radius. We will come back to them.

06:12 If we look at the posterior view of the humerus then there is not as much detail here.

06:17 Once again we can see this is a right humerus. We are now looking at the posterior surface so here again is the medial aspect and here we can see we have got the lateral aspect.

06:29 The head of the humerus pointing medially to articulate with the glenoid cavity.

06:34 We can just see now the greater tubercle, we can't see the lesser tubercle, that's more on the anterior aspect and we can’t see the intertubercular sulcus. But we make out the position of the anatomical neck between the head of the humerus and greater tubercle and distal to the greater tubercle we can see the surgical neck.

06:53 We will come back to the surgical neck cause it has some important structures running around it, and therefore fracture of the surgical neck can lead to some important functional deficits. An important structure that we can see on this posterior aspect is the radial groove that is passing down this posterior surface. We can see the radial groove.

07:17 And the radial groove is important, it allows the radial nerve and the profunda brachii artery to run alongside as they supply the posterior compartment of the arm.

07:28 So we can see the radial groove here is on the shaft of the humerus on its posterior aspect. We can also again see the medial supracondylar ridge. We can see the lateral supracondylar ridge and they have given rise to the medial epicondyle and the lateral epicondyle. We can see here. So the radial groove medial and lateral supracondylar ridges giving way to the medial epicondyle and the lateral epicondyle. Same features we can see on the anterior surface.

08:03 If we look at the posterior surface of the distal humerus we can then see that we have the olecranon fossa and this is an important shallow depression for the olecranon which is a bony structure on the ulna and we look at that next as we look at the ulna.