In this video, we're going to examine the thoracic cage. Now, the function of the thoracic cage primarily is to protect vital organs of the thoracic cavity. This, of course, includes the heart, the lungs, and major blood vessels. It's also there to support...
the shoulder girdles, so the clavicle and all the bones associated with the scapula and the shoulder joints, as well as the upper limbs. And then lastly, it provides attachment sites for a number of muscles for the neck, back, chest, and shoulders. And so when we look at the thoracic cage, on the posterior side, it is made up of the spine. thoracic vertebra that we talked about in the previous video. On the anterior end it's made up of the sternum and we'll go into a little bit more detail about the sternum but also the costal cartilages that connect to the sternum and then on the flanking sides the lateral sides you have the ribs.
So let's look at the sternum or the breastbone. It is made up of three main components, three bones that are fused together. The most anterior, or the most superior portion, excuse me, is going to be the manubrium. So here is our manubrium, and when we look at the manubrium, it has a couple of telltale signs. So the first landmark is the clavicular notch.
So this is where... clavicles will articulate. So the clavicles or the collarbone will articulate on either side.
Then you have the jugular notch. You can actually feel this if you palpitate down and you feel this indentation right here. That indentation is referred to as the jugular notch.
So this roughly corresponds to If we look at the jugular notch, the disc between vertebra T2 and T3, and this is where sort of the carotid artery is going to come through. So that's sort of the manubrium. The first two ribs, first pair, two pairs of ribs will articulate.
You can see. The first rib completely articulates with the manubrium, and then the second rib partially articulates with the manubrium. Then you have the main part of the breastbone, which is the sternum. So the sternum is going to articulate with costal cartilages from ribs 2 through 7. So one of the landmarks here is the intersection between the manubrium and the body.
This is called the sternal angle. So this corresponds roughly to T4, T5. This is a cartilaginous hinge joint that allows sort of the anterior movement of the breastbone during deep inhalation.
So the last component then is the xiphoid process that forms the inferior end of the breastbone. Mainly it is a site of muscle attachment. There are no ribs attached to it.
So that's something to note. So no rib attachment. And in our youth, the xiphoid process is actually made up of hyaline cartilage. But in adulthood, it will become ossified. roughly around the age of 40. Oddly enough, in conjunction with those costal cartilages, they will also ossify at that point.
So the last sort of landmark here is the xiphol sternal joint. This is the point where the sternal body will meet the xiphoid process. So this is going to correspond roughly to... the thoracic vertebrae number nine and just deep to this is where the part is going to lie. So let's now look at the various ribs.
So we'll kind of jump between this particular figure and the figure before. So we have 12 pairs of ribs. Those ribs are going to be attached to primarily the breastbone as well as the thoracic vertebrae. So if we look at the points of attachment on the posterior side to the body.
They're going to be connected to the transverse processes of the thoracic vertebra. So if you remember our earlier discussion about the thoracic vertebra, you have the transverse costal facet. So this is the point of attachment for the tubercle of the rib. And then you have the superior costal facet, which is going to be attached to the head of the rib. So we'll go into the specific components of the rib in the next slide.
And then on the anterior side, via the costal cartilage, you're going to be attached to the breastbone. So if we look at the ribs... the first seven pairs of ribs, pairs one through seven, these are known as true ribs or vertebro sternal ribs because they are going to be directly attached to the sternum by the individual costal cartilages. So again if we're looking at, and we can kind of number this down the line, we have one, two, three, four, five. Six and seven.
So these are all true ribs because the costal cartilage directly connects to The breastbone. However, if we look at pairs eight through twelve eight through twelve So if we go down the number here eight through twelve Notice how the connections the costal cartilages are making. They're not making it directly to the breastbone.
They're making it to the costal cartilage of another rib. So pairs 8 through 12 are known as false ribs. And we can kind of define that even further.
8 through 10 are called vertebrochondral ribs. since they are attaching to the costal cartilage of the rib above, as I showed over here. And then the last two pairs of ribs, so ribs 11 and 12, notice that those particular ribs do not have any kind of attachment to the sternum.
So there's no costal cartilage associated with it. So if we examine the specific parts of the rib, Again, the majority of the rib is going to be the shaft of the rib. So let's actually move to this next slide here.
So the majority of the rib is going to be the shaft. The junction will connect to the costal cartilage. Then you have the head of the rib. So the head of the rib, this is where you form the articulations with the vertebra.
So look at where the head is located. specifically at the superior costal facet. That's where the head of the rib is. So again, let's make a note of that. The superior costal facet of the thoracic vertebra is going to articulate with the head of the rib.
And then the articular facet on the tubercle of the rib is over here. So we have two points of articulation. Okay, so just to go over this again, the head will articulate with the facets or the demi-facets on the two adjacent vertebra.
The neck is the constricted portion beyond the head. The tubercle is lateral to the neck that will articulate to the transverse costal facet. And then the shaft is the majority of the rib.