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Centriacinar emphysema vs panacinar emphysema

Video transcript
Voiceover: So the two categories that we assign to emphysema, the centriacinar and the panacinar, they're basically referring to geography. It's like saying, my city's flooded, and is it contained to the central streets, the main street, or is it everywhere? So basically, it's asking, "Where is the emphysema?" So a little Latin review, we have "pan," which means everywhere, and "centri," so "center." Now, what on earth is an "acinar?" And basically, that's a geographical term too, and this is an "acinus." To orient ourselves, let's draw the lungs. We have the trachea here, and the two big bronchi, so you have your lobe of lung here, and lobe of lung here. The bronchi are kind of like your tree trunks, and as they start to branch off like this, the smaller airways here are called "bronchioles," and that's basically the level we're at right here. Here is our bronchiole, and the rest of this branch that I've drawn, is just the rest of the airway. So here, we have our alveoli cluster. So there are many many countless branches of acini in the lungs, but this is what one would look like. So that tells us centriacinar versus panacinar, we're talking about where, in this, are we? So in this normal acinus that I've drawn, you can see the tightly, little coiled structures here in the alveoli, and along the airways too. This elastic, coiled shape is possible because of our protein, elastin. Elastin is cleaved by elastase, which is this protein inhibitor, which is good usually, because we want the tissue to turn over, old ones to be eaten up. And this whole system is controlled by Alpha 1-antitrypsin, which is a compound made in the liver, and it's job is to regulate the amount of elastase. So, by inhibiting the elastase, it inhibits the elastin, the antitrypsin lets there be more elastin. So whether we're going to have centriacinar here, or panacinar destruction of elastin, fully depends on the pathophysiology of why is there so much elastase? Why is elastin getting destroyed? So first, let's take a look at centriacinar. And this is what it looks like, so I've draw the same acinus that we have up there, but because of the lack of elastin in it, there're fewer of the walls to begin with. And, whatever walls there are left, it's because it's so floppy, that's why it looks bigger like that, it just doesn't hold that nice shape. So this is what we call "centriacinar distribution," as you can see, geographically, it's earlier, it's not everywhere. Centriacinar is really related to inflammation, which is the first pathophysiology of emphysema. Now inflammation recruits neutrophils, these white blood cells that flight inflammation everywhere in the body. But when they get to the lungs, the neutrophils make elastase, that's the whole culprit here. So it's too much elastase, from too much inflammation. And the way we'd get that, most commonly, is from smoking. So even though, when you see somebody smoking, and the smoke rising out of there looks like just some sort of gas, it's actually made of millions of tiny little particles, that enter the lungs. They're all foreign, they're all irritating, and the lung acts like a filter, these smoke particles are big enough to get trapped pretty early on. They're not small enough to get through the filter, all the way to the end of the acinus, so they kind of stay in this central acinar distribution, which then makes sense, that central acinar is related to smoking, and the inflammation you get from that. So if you look at the lungs as a whole, centriacinar is early on, and near the larger-caliber airways, like the bronchioles. Now the next one, panacinar. So panacinar is usually not induced by some sort of external factor; this problem arises out of the body itself. Here we have Alpha 1-antitrypsin deficiency. Remember, we said up there, this regulates the amount of elastase, namely to tone it down a little bit. So without it, the elastase is really unchecked; it just goes nuts, and eats up all the elastin in the tissues, everywhere. See this problem [unintelligible] earlier or later in the lungs, because it's inherent in all the tissues of the lungs. So everywhere the elastin's getting chewed up, everywhere there's elastic tissue. Just as a side note, Alpha 1-antitrypsin is made in the liver, and in this disease, when there's deficiency, that means something in the DNA, and the gene encoding for it, there's a mistake. So, all the misfolded protein can't leave the liver, leading to liver disease. But when we come to the lungs, we see panacinar emphysema.