Ulna – Bones and Surface Anatomy of Upper Limb

00:00 So this is the ulna bone which we can see in isolation. It sits within the forearm alongside the radius.

00:08 And we can see we have a number of views here that reveal various bony landmarks.

00:15 So let's have a look. The ulna is longer than the radius and within the forearm it is involved in stabilizing the forearm and of the two bones it's positioned medially. So the ulna is medial and the radius is lateral. Here we can see the anterior view, here we can see a posterior view and this view is as if we're looking at it from the radius.

00:41 So as if we are looking at it from the radius is positioned. We can see it is really a lateral view as if we were the radius and we have got some features I would like to detail. So proximally, up here we have the olecranon we can see that here on the posterior surface and here on this lateral view we can see the olecranon and not proximal kind of extension of the ulna helps to form this C-shaped cavity and this C-shaped cavity is known as the trochlear notch. We can see we've got the trochlear notch here. We can see we've got the olecranon, the C-shaped notch which gives rise to this coronoid process. And just remember, on the anterior surface of the humerus, we had the coronoid fossa while this enables the coronoid process to sit in it when the forearm is fully flexed. So we can see the coronoid process here when the forearm is fully flexed. So the forearm is sitting against the arm, the coronoid process can sit inside the coronoid fossa and that add stability to the flexed forearm.

02:04 So we have got the olecranon which we can see, we have got this C-shaped trochlear notch and we have got this coronoid process. The trochlear notch is going to articulate with the humerus, specifically the trochlea of the humerus. So we have got this kind of barrel shaped trochlea of the humerus and that is going to allow articulation with the trochlear notch. We can also see the coronoid process, we can see it here on the anterior process we can see it here posteriorly sticking out somewhat. Laterally, we can see we have the radial notch, the radial notch here on this anterior view and we have got the radial notch here on this lateral view. And that is important because that is going to receive the head of the radius.

02:55 We also have this crest running down here, known as the supinator crest and that offers the attachment of supinator muscle. More inferiorly from the coronoid process, we find we have the tuberosity of the ulna and we will come back to that in a moment.

03:11 So some important bony landmarks we can see on this proximal region of the ulna.

03:18 If we look at the shaft of the ulna then that is not the great deal to really mention just that it has a sharp interosseous border. So here we have got the anterior view, we've got this anterior surface running down here. And we can see we have got the sharp interosseous border.

03:36 We can see it quite prominently here on this lateral view. The interosseous border is important because it allows the interosseous membrane to run between the radius and the ulna.

03:48 Distally if we look at the ulna we have the head, a rounded head and then we have the ulnar styloid process and this sticks out we can see here on the posterior surface. We can see it here and on this anterior view we can see the ulnar styloid process sticking out.

04:07 And this can be palpated medially at the wrist joint. The distal end of the ulna does not articulate directly with the carpal bones. There is an articulation there but it's separated by an articular disc. And we will come back to that when we look at the joints.