So this is a quick tutorial on the sternum. The sternum consists of three parts. You've got the manubrium of the sternum, the body of the sternum and the xiphoid process inferiorly.
We’ll begin by taking a look at the manubrium of the sternum first. This is this superior part of the sternum. You can see it has two articulations. You've got articulations with the clavicle and with the first costal cartilage here. There are features of the manubrium that you need to know about.
Superiorly, you've got this little notch up here which is called the suprasternal notch because it's above the sternum, at the top of the sternum. This is also sometimes called the jugular notch.
And then you've got a facet here on the superior and lateral aspect of the manubrium, which is for articulation with the proximal end of the clavicle. And for its articulation with the first costal cartilage, we've got a facet for this attachment.
And then right at the bottom of the manubrium, you've got a little demifacet. 'Demi' just means half. We’ve got half a facet here for articulation with half of the end of the second costal cartilage. Obviously, this means that there must be another demifacet. The other demifacet is just below on the top of the body of the sternum. This articulates with the bottom half of the second costal cartilage.
On the manubrium, you've got the sternal notch superiorly. Then you've got facets for articulation with the clavicle and the first costal cartilage. And then you've got a demifacet at the bottom of the manubrium for articulation with the top half of the second costal cartilage.
And importantly, where the manubrium meets the body of the sternum, you get this angle called the sternal angle. This angle is often called the Angle of Louis and it's an important anatomical landmark. I'll do another tutorial which talks about the important structures that can be found at the sternal angle. The sternal angle lies at the level of the intervertebral disc between thoracic vertebra, T4 and T5.
Moving on to the body of the sternum, you've got this large flat bone. Along its lateral edges, it's got articulations for the costal cartilages.
Remember the demifacet at the top of the body of the sternum for articulating with the bottom half of the second costal cartilage, there's also a demifacet at the bottom end of the body of the sternum. This articulates with the top half of the last two ribs, so the 7th rib.
Remember, you've got seven true ribs – so one, two, three, four, five, six, seven. These ribs have their own costal cartilage for articulating with the sternum.
At the top, you've got the demifacet articulating with the second costal cartilage. And then you've got facets for articulation with ribs three, four, five and six. And then right at the bottom of the sternum, you've got another demifacet articulating with the 7th costal cartilage.
The other demifacet lies on the xiphisternum. The xiphisternum is this little process at the bottom of the sternum, inferiorly on the sternum. And between the body of the sternum and the xiphoid process, you've got this fibrous joint.
That’s all there is to it really. That's a brief outline of the sternum.