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Emphysema pathophysiology

Smoking and air pollution cause the alveoli in the lungs stiff and less stretchy, making it difficult for air to escape during exhalation. Learn how the destruction of the protein elastin is key to the progression of emphysema, and how the over production of elastase occurs. Created by Amy Fan.

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Video transcript

Voiceover:The pathophysiology of emphysema, which it just means the disease crosses behind it. How do we get from a normal lung to having emphysema? I would say, in a nutshell, it's the destruction of elastin, which is this protein in the lungs that gives it that nice elastic quality. Elastin, elasticity. So, elastin kinda looks like a coil. I think of it as a coil. And actually if you look at the protein itself, it looks kind of coiled like that. And when you take a coil and you stretch it like that, with force, and then you let it go, what happens? It immediately snaps back into the original shape and size, right? Because it's elastic. The elastin in the lungs allows it to do just that. So the top of a breath, the alveoli, which are these air sacs at the end of the airway, they look puffed up and full of air, like this. And this is just like our stretched out coil. And because the walls are full of elastin, when you exhale, which is just relaxing, the air comes out by itself and the area kind of goes back to its original shape and size. Kind of like that. So there's not that much air left in here. But, like I said, in emphysema, all the elastin is getting destroyed so we have fewer of these nice walls and whatever is left, is no longer elastic. So the top of a breath, it might look like this. Do you see how the partitions and stuff are gone? But what's worse is when you let go. Not that much changes. It's like a spring without the elastic quality. It's just a wire. So when you let it go, it's just gonna sit there. And all that air in here is further obstructed because the airway here actually collapses. It collapses because without the elastin to hold it open, the pressure in the chest cavity, that acts on the airway, collapses it. That's why we say in emphysema, you have obstructive lung disease because the air is obstructed back there. So in a normal, healthy, functioning lung the elastin is actually normally being broken down all the time. So elastin is broken down by elastase which is a protease inhibitor, and by that we just mean something that breaks down protein. So the job of elastase is to cleave the elastin so that new tissue will have room to grow. And who's going to keep track of elastase is something you would call alpha one antitrypsin. It's something that's made in the liver, and again I'm gonna use red, because it inhibits elastase. So if it inhibits the thing that inhibits elastin, then the relationship here is gonna be alpha one antitrypsin allows there to be more elastin. It's kinda like in the ocean, if you have shrimp here at the bottom of a food chain, and it's eaten by a small fish. It's eaten by, let's say, Nemo. So, red Nemo eats fish. And then behind it, there's a big fish. Maybe I shouldn't call that Nemo. So, just a big fish, let's say a shark, eats this small fish. So in this food chain, the relationship... If the food chain is this simple, then the big fish, or the shark, allows there to be more shrimp by eating up all the small fish. It's kinda like that with elastin and elastase and alpha one antitrypsin. And our whole problem here with emphysema is too much elastase. Too much elastase leads to emphysema. Now in terms of too much elastase there are two main ways to have that. Anytime you see "ase" here, A S E, that's usually a protease inhibitor so it destroys a certain kind of protein. Number one here we have inflammation. And any time there's inflammation in the body, it's kind of like a war is breaking out and all these soldiers are being recruited and one main one is called a neutrophile. It's a type of white blood cell that's always in the blood and when there's inflammation, it goes there. And more importantly for us right now, it's the mother of elastase. Literally the mother because it makes elastase. So whenever there's too much neutrophils in an area, it's gonna go nuts making elastase. Inflammation is usually in response to an invading foreign thing, right? It could be bacteria or just any kind of particles. And in here, especially in the lungs, the big culprit is gonna be smoking because even though you see the smoke rising from cigarettes looks like just air, but it's actually made of millions of billions of tiny little particles that gets inhaled into the lung. So there's inflammation all the time. What I drew there actually looks more like a fake cigar, but you get the point, is that anytime you're putting extra irritants into the area, inflammation's gonna go rampant, and our elastase shoots up. So number two, the second reason is something that arises from the body itself, which is something called alpha one antitrypsin deficiency. We don't have this in the lungs. This is the equivalent of taking out that big fish in the food chain. So this small fish is gonna go up without the big fish eating it and the shrimp, poor shrimp, they're all gonna be gone. Now alpha one antitrypsin is made in the liver and is coated by a gene. And this deficiency here is related to a defect in the gene because the gene has a problem here and when it's made in the liver, the antitrypsin becomes [unintelligible] and it can't leave. It doesn't fit through the channel for the normal antitrypsin to leave so this actually causes liver disease, but in terms of the lungs, again we have too much elastase because it's unchecked. And again, with the elastase going nuts here, our elastin's gonna go down. And you have emphysema.