The Thoracic Cage - Video Tutorials & Practice Problems
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concept
Thoracic Cage
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We're gonna finish up the axial skeleton by talking about the thoracic cage, the thoracic cage or which you probably just know it as the rib cage, the rib cage or thoracic cage is there to protect the thoracic cavity. Remember the thoracic cavity that cavity inside your chest that houses importantly your lungs and your heart. Now, it's also just gonna provide structure for your body and really importantly structure for the lungs. Your lungs do not work without ribs. We'll talk about that more in the respiratory unit. All right. So the thoracic cage is gonna consist of the thoracic vertebra, those 12 vertebrae that articulate with ribs that we talked about previously, plus the ribs, the sternum and the intercostal cartilage. And we have those things color coded over here in our image. We can see the thoracic cage, we can see the vertebrae here. We also have drawn on here, the collar bones and the shoulder blades just for reference. All right. So let's talk about the ribs, the ribs are gonna be 12 pairs of flat bones that wrap the chest. Now, quick little misconception check. I've heard some people say before that females have one less rib or one less pair of ribs that comes from the Adam and Eve story, regardless, it's not the case. There's no difference between, in between sexes in terms of number of ribs. Now, some people have an extra pair of ribs, but that's just a rare bit of human variation, right? So you have 12 ribs, 12 pairs of ribs and we can number them just like we did the vertebrae counting down from the top. So we have rib number 12345. So on down to 12, and we're gonna say the first seven ribs, ribs, one through seven, we're gonna call the true ribs. So those first seven ribs are called true ribs because they attach to the sternum directly via their own piece of costal cartilage. And we can see that on the image, we go 1234567, those first seven ribs, which are a little bit that darker pink. There you can go across and trace a piece of costal cartilage over to the sternum and it doesn't connect to any other piece of cartilage. It just goes sort of straight over to that sternum that's going to be different for the five bottom ribs. So the five bottom ribs, we call the false ribs and they attach the sternum either indirectly or not at all. So the first three false ribs, we can look and we go one right here, 123, you can see they have that costal cartilage attachment, but the costal cartilage connects to other costal cartilage before it connects to the sternum. Now, the last two false ribs we call floating ribs and that's because they have no sternal attachment. So we can look here just like all ribs. They articulate with the vertebrae posteriorly. But these last two ribs in this dark pink labeled one c, they have no connection anteriorly to the sternum, right? Knowing the difference between true false and floating ribs is a question that you'll often see. So I'd really be familiar with it. Next up, we have the sternum, which we've been talking about a little bit. Your sternum also just called your breastplate sometimes. Well, this is gonna be a flat bone and we can see it in purple here in the drawing. I always think it kind of looks like a necktie. Now, this bone that, that this flat necktie is actually made up of three bones that fuse together and you're probably gonna need to know those individual bones. So what I think of sort of the knot of the necktie up here to a, that's the manubrium, the sort of long part of the necktie, that's the to be a body. And then this little tip sticks down off the bottom to see there. That's the xiphoid process and you can feel your xiphoid process, it sticks down a little bit, it kind of hurts to press on it serves as an attachment point. Now to help. Remember those I have this little memory tool. If you need it, you can say I'm gonna mark the body with an X, mark the body with an X, the manubrium, the body and the Sipho process. All right. Lastly, we're gonna talk about the intercostal cartilage, which we've already talked about some. But the intercostal cartilage is gonna connect those ribs, one through 10 to the sternum. So the seven true ribs plus the first three false ribs and it is there, it is a sh uh flexible and strong connection, flexible, right? You do have a little bit of flex in your rib cage and some of that, a lot of that comes from the flexibility of the costal cartilage and those joints there. But it also has to be really strong because it's protecting what's inside your thoracic cavity and giving structure to your body. All right with that, that's the thoracic cage, like always example and practice problems to follow. I'll see you there.
2
example
The Thoracic Cage Example 1
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2m
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Our example tells us that the image below shows two ribs. One is rib 10 while the other is rib 11, how can you tell which is which? All right on its surface? This sounds like a really hard question. And you should not need to be able to just pick up a random rib and say what number rib it is one through 12. But think for a second, what is different between rib 10 and rib 11? Well, when we count the ribs, we count the pairs of ribs from the top. So rib pair, number one is at the top ribs, 12, they're at the bottom as we count down. Remember those first seven ribs, those were your true ribs and those pairs of ribs connect to the sternum directly with their own little piece of costal cartilage that connects them to the sternum. The last five pairs of ribs, we call the false ribs. And that's because they do not connect to the sternum directly or they don't connect at all. Either they have costal cartilage that comes up and connects to other costal cartilage before running into the sternum or they don't have any costal cartilage attachment to the sternum at all. It's those last two ribs, which we called the floating ribs that have no costal cartilage attachment. So with that in mind, what do you think is different between 10 and 11 and take a look at the picture? What cues you in into which is which? Well, as I look at the picture I see here, this rib in the front, it has this sort of blunt section and it looks like it has some cartilage there where this one just comes to a point. Well, rib 10 is going to be a false rib, but it's gonna have costal cartilage that runs up and connects to other cartilage and eventually runs into the sternum. So when I see this blunt end in that cartilage there, that tells me this one must be rib 10. And my reasoning, I'm gonna say it has cartilage attachment. Now, in contra, I look over here, this rib ends in a point. It's not attaching to any cartilage. So that must be one of my floating ribs. A floating rib is gonna be rib 11 or 12. But here it tells us it's rib 11. So my reasoning, no cartilage attachment again, you shouldn't have to be able to just pick up a single rib and say what number it is one through 12. But you should be familiar enough with ribs that you can describe the difference between those true ribs, the false ribs and then among the false ribs, what's different about the floating ribs? There we go.
3
Problem
Problem
When giving chest compressions during CPR the thoracic cavity can flex in and out without breaking bones. What is one reason that the thoracic cage is able to flex in this manner?
A
Flexible costal cartilage comprises a large portion of the anterior thoracic cage.
B
Ribs have a curved shape allowing them to flex and bend easily.
C
The floating ribs have no connection to the sternum allowing the thoracic cage to change shape easily.
D
The sternum is made of three bones that can easily bend where they form joints with each other.
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Problem
Problem
What makes false ribs different from true ribs?
A
False ribs do not articulate with the costal cartilage.
B
The costal cartilage that connects to true ribs connects directly to the sternum.
C
The true ribs articulate with the sternum, while false ribs do not.
D
False ribs articulate with costal cartilage but are not connected to the sternum.
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