Overview of the humerus and scapula.
Hello everyone! This is Joao. Welcome to Kenhub.com where learning anatomy becomes easy. Today, I’m going to be covering the humerus and also, later on on this tutorial, the scapula.
Now, what I’m going to be doing on this tutorial and the future tutorials is I’m going to be giving you the terms in English, but right after it, I’m going to show you how you do it in Latin, how you will use the Latin terminology to refer to these structures, because as you know, Latin is the universal language of anatomy.
Now, let’s start, and the first thing that I need to pinpoint are the articulations that are happening between the humerus and other bones, and proximally, you can see that the humerus is articulating with this triangle-shaped bone here known as the scapula. And distally, it is articulating with the ulna and with the radius.
So we are looking at the anterior view of the humerus, and the first structure that you can clearly see here is the head of the humerus, and I’m highlighting it, so you can see that it’s articulating here with the glenoid cavity of the scapula. Now, laterally, you can see this prominence known as the greater tubercle, and medially, you’ll find another prominence, a smaller one, known as the lesser tubercle.
Now, as you can see, if you go down, this is forming a crest. So the greater tubercle is forming a crest here and is known as the greater tubercle crest or the crest of the greater tubercle. And also, the lesser tubercle is forming another crest known, of course, as the crest of the lesser tubercle. Now between these two crests formed by these two tubercles, you will find a sulcus known as the intertubercular sulcus and is also known as the bicipetal groove. And it’s known as the bicipetal groove because this is where the long head of the biceps brachii, the muscle biceps brachii will go to, and I want to show you.
So this is the muscle, and the long head is going through this intertubercular groove or sulcus.
If we move distally, we’re going to find here a tuberosity, and this is known as the deltoid tuberosity. And as the name indicates, this is where the deltoid muscle is going to insert. So you have here an image of the deltoid muscle, and it’s using the deltoid tuberosity on the humerus to insert.
Now, moving further to a more distal point, you’re going to find a fossa here known as the radial fossa and is located laterally. Now, on the medial side, you’re going to find what is known as the coronoid fossa. Now, here, you will also find a structure that is known as the—I’m going to change the color here—this is known as the capitulum, and this is what’s going to articulate, this structure is going to articulate with the radius. And on the opposite side medially to it, you’re going to find another structure known as the trochlea, and this is what’s going to articulate with the ulna.
We are now looking at a posterior view of the humerus where you can still see the clavicle here and the scapula, also on their posterior views. And the first structure that we also saw on the anterior view was the head of the humerus, so you can still see it here. Now, a little bit more laterally or more distally, you’re going to find another important structure right here known as the anatomical neck. Now, a bit further laterally, you’re going to find the greater tubercle that you could also see on the anterior view. More distally, you’re going to find another neck known as the surgical neck, and you can notice here a groove, or a little bit of a depression. This is where the radial nerve is going to pass through let’s say. This is known as the radial groove.
Now, you can also still notice the deltoid tuberosity here laterally where the deltoid muscle is going to insert, and a very important thing that I need to clarify here, and I forgot to mention on the anterior view, is that this long area here of the humerus, this is known as the body or shaft of the humerus—very important.
Now, if we go further down or more distally, we’re going to find a few structures that are important mentioning. The first one is the medial supracondylar ridge, and you will also find the lateral one—so a lateral supracondylar ridge. Now, you’ll find here the… what is known as the medial epicondyle, and you will also find a lateral epicondyle. One important thing to notice here is this depression that you find medially on the medial epicondyle. We call it the groove for the ulnar nerve.
Now, you see a very clear and noticeable—I’ll choose a different color here—very noticeable fossa here. This is known as the olecranon fossa. And right beneath it or a bit more distally, you will find what is known as the trochlea. So this is known as the trochlea of the humerus.
Now that we’ve just completed the humerus, it is time to move on to this flat triangular-shaped bone known as the scapula, seen here in green. It is also known as the shoulder blade because it is one of the major bony components of your shoulder.
Now, in this image here, you can also see two other bones that articulate with the scapula. The first one located laterally, this is known as the humerus, and also, superiorly, you can find the clavicle. The humerus is articulating with the glenoid cavity of the scapula, and we’re going to see and talk about this structure later on on this tutorial. And also, it is important to know that the clavicle is articulating with the acromial process of the scapula.
So before we go on, and define, and talk about the different bony structures that you find on the scapula, we need to talk about the borders and the angles that you find in this bone. Now, what I have here is an anterior view, also known as a costal surface of the scapula, this is the front part, let’s say, of this bone, and I’m going to provide you with the posterior view or the backside of the scapula as you can see here on this second image.
Now, let’s first define the angles, and there are two that you need to know. The first one is the inferior angle, highlighted in yellow, and the second one is the superior angle, highlighted in blue.
Now, once we define these two angles, let’s talk about the borders, and there are three that you need to know. The first one is known as the medial border. This is the longest border, and as you can see here, it will extend from the superior angle, all the way down to the inferior angle. Now, the second border that you need to know is the lateral border, which will go from the lower margin of the glenoid cavity, which is a structure that is articulating with the head of the humerus, that we’re going to learn about later on this tutorial, and goes all the way down to the inferior angle. Now the last one is the superior border. This is the shortest and the thinnest and will extend from the superior angle, all the way to the base of the coracoid process as you can see here.
Now, it is time for us to talk about the bony features of the scapula, and we’re going to start with the image to your left, and this is the anterior or costal surface of the scapula. Now, it’s important to notice that, here, you’re going to find a structure that is specific or specifically seen on the anterior side of the scapula. This is a flat and slightly concave feature or structure known as the subscapular fossa.
Now, if you look to the image on your right, this is the posterior view of the scapula. And here, you can also see a few structures that are specific to the posterior side. And the first one is the spine of the scapula, which is also highlighted in blue. And the spine of the scapula is almost like dividing two other important structures that you find on the posterior side of the scapula, and these are the supraspinous fossa—“supra” meaning above the spine—and also and infraspinous fossa, meaning below the spine. Well, one important note here is that the infraspinous fossa is much larger than the supraspinous fossa.
Now, another feature that we need to highlight here is if you notice here on the spine of the scapula, you’re going to find a triangular base medially which rises laterally to terminate in a flattened process, and this is the famous acromion, highlighted here in yellow. Now, for your own knowledge, I want to tell you that the acromion forms here an angle known as the acromial angle, and this is a palpable bone point on your body.
The next structure that we’re going to talk about is known as the glenoid cavity, highlighted in green. This is a very important surface located laterally on the scapula, and this surface will articulate with the head of the humerus, as you can see here on this image, and of course, a very important articulation happening in your shoulder joint. Now, the other structure that you’re going to find here is a small projection at the upper boarder of the glenoid cavity. This is known as the supraglenoid tubercle. And then below the glenoid cavity, you’re also going to find another tubercle known as the infraglenoid tubercle.
Now, you’re going to find another structure adjacent to the glenoid cavity. This is known as the neck of the scapula.
The next structure that we’re going to talk about is found above the glenoid cavity, and this is known as the coracoid process. And as you can see here on this image, the coracoid process is bent at a right angle lateral ventrally and has a flattened tip, as you can see here. Now, another important thing to know about the coracoid process is that this structure, alongside with another structure that we talked about, the acromion, these two will perform a very, very important function—is that they will protect the joint that is found beneath them. This is a very, very important joint known as the shoulder joint. So this is one important function that these two structures will perform together.
Now another structure that we want to talk about briefly is found also on the posterior side, and this is known as the suprascapular notch, highlighted in red as you can see here. And the suprascapular notch is medial, so it’s found medial to the coracoid process or to the base of the coracoid process, and it’s on the superior margin of the scapula or the superior border.
Now, this is the end of the tutorial, but before we go, I have to give you important notes on the location of the scapula on your body. And the first point that I want to make is that the scapula lies on your thorax. The second point is that the base of the spine is at the same level of the third thoracic vertebra. The third point is that the inferior angle of the scapula lies between ribs seven and eight. And the fourth and final point to make on this tutorial is that, when your arm hangs down, the medial margin should be parallel to the row of the spinous processes on your vertebrae.
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