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Thromboemboli and thromboembolisms

Clarifying difference between a thrombus and an embolus (and between thrombosis and embolism). Created by Sal Khan.

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Video transcript

I want to clarify some of the terminology I used in the last video. But before I do that, let's just make sure that we understand the mechanism of how arteries can get blocked. So in the last video, we talked about these plaques forming. And if this plaque is unstable, at some point it could rupture. And when it ruptures, this material can start to flow out into the bloodstream. And two things will happen. I just want to make it a little bit more clear relative to the last video, especially now that I can zoom in on these arteries. Two things could happen. Plaques-- or I should say clotting, not plaques. These are the plaques that have been released. The clotting factors can kind of clot these released pieces from the plaque. And the other thing that can and often will happen-- and I didn't talk about this in depth in the last video-- is that you an also have-- when this thing ruptures, you can also blood clots form here. Let me do this in a more reddish color. So you can also have blood clots form on the ruptured plaque. So everything, even the plaque, the part of the plaque that has not begun to move, can experience clotting. And also the part of the plaque that's kind of been dumped into the bloodstream can also clot. In the last video, we saw that one of these clots can go downstream to some point where the arteries get narrow enough so that they actually block the artery right over here, and that just restricts the blood flow. So now all of a sudden, you don't have any blood flow going downstream. And all of this muscle tissue that needs the blood flow from this point, that needs to get oxygen from that, it might die. And you might have a myocardial infarction or a heart attack. Now, what I want to clarify is the actual terminology. I guess, I was a little bit hand-wavy with the terminology. I want to get a little bit deeper here. This actual clot that forms that can restrict the blood vessel, this right here is a thrombus. Thrombosis is the process of a thrombus forming, so thrombosis are these blood clots that form that can actually help to kind of obstruct a blood vessel. So this thrombus right here is actually going to make it harder for the blood to flow through this vessel. Now, any of these released pieces or chunks in any of these blood vessels that can float around and eventually lodge themselves in and eventually block the blood flow, these are called emboli. Or if I just use them in the singular, one of these is an embolus. And I want to be clear. An embolus is the general term for anything that can float around in your blood and eventually lodge itself, at some point, in your circulatory system and restrict the blood flow. What we drew in the last video-- and in particular, this one as well-- is that these emboli that are also clotted-- so they're also kind of thrombus-- they're are thrombi and emboli at the same time. This right here would be called a thromboembolus. These words are strange to say sometimes. So it wouldn't be wrong to call it an embolus. But in particular, when we say it's a thromboembolus, you know that it's kind of this clotted material around this release plaque that can go lodge itself. And in the last video, I called this a thrombosis. But that was really not quite right. The thrombosis is really the formation of the clot that can restrict the blood flow. When it actually lodges itself further, when it actually breaks off, becomes an embolus, and lodges itself further often restricts blood flow, this is called a thromboembolism. Let me write this. So hopefully I'm not confusing you too much. These medical terms confuse me a lot, but I want to make it very clear. Thrombosis is just the general formation of a blood clot inside of a blood vessel that can restrict the flow of blood. So this right here, this is thrombosis occurring. That is thrombosis. Once things break off and they start floating around, they're an embolus. That's the general term for it. And in particular, if it's broken off material that is due to a clot, it's a thromboembolus. So thromboemboluses are a more specific way of calling it an embolus. And once one of these things lodge themselves and block the blood flow, that's a thromboembolism. You can also call that an embolism. Just when you say it's a thromboembolism, it makes it a little bit more specific to know that it's kind of clotted material. So hopefully that clarifies things and doesn't confuse you too much.