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Current time:0:00Total duration:10:19

Video transcript

let's say that these are your lungs this is your right lung this is your left lung I'm just going to label them upper and this will be lower and this will be the middle lobe and you're minding your own business in somebody coughs and they get TB in your lungs so that TB gets inhaled you breathe it in and the location that the TB likes to go to is actually a pretty interesting thing is it likes to go along these fissures that I'm drawing out here so these are the fissures they separate the lobes of the lung right they're kind of like the boundaries and so they like the TB bacteria they like to go near those fissures and they also actually like to go sub plural plural it kind of indicates the outside layer of the lung so if it's SOB it's right underneath that outside layer so they like to go somewhere along the fissure and somewhere in the sub pleural space kind of right on the edge so they're going to jump into some alveoli let me just draw it out for you here and you know you've got millions of these guys so I'm going to draw out a few mores to make it really clear that these things are in packs and what's going to happen is that of course you're going to have an immune response right away to this bacteria that's in there so you might have a macrophage coming along like that and this macrophage is going to pick up the bacteria that's now landed inside of that air sac and it's going to take a journey through the tissue of the lung and it's going to go and drain down to a local lymph node so this is a local lymph node kind of a neighborhood lymph node let me label it right here lymph node so that's the journey that the macrophage is going to make not every single one but some of them are going to go to the lymph node and what they do by doing that is to actually carry with them the micro bacterium right so this little bacterium is now carried along going for the ride and now the bacteria is in two spots it's in the original spot where landed in the lungs but it's also in the lymph node because I got carried there by the macrophage and I should have mentioned this earlier but let's assume that this is your primary infection in other words this is the first time that this person or guess it could be you or me is breathing in the TB bacteria so what's going to happen is that there's going to be a reaction the micro bacterium and the macrophages are going to start warring they're going to fight and you're going to get this entire area turn into literally like a battlefield with dead Mycobacterium and some dead macrophages so some of your own cells are going to be part of this but a lot of it is just going to be the bacteria right and you're going to get some of this battlefield going on over here as well in this lymph node so that's what it's going to turn into giant battlefield and if you look under a microscope it actually looks like what we call it a granuloma that's the description that a pathologist might use for for what we're actually describing here and same thing is true for the lymph node there's a little granuloma in there as well if you were to peek inside of this granule but let's just actually kind of erase the center out if you were to peek inside of let's say I was to cut it open what you would see is inside of this granuloma is literally like this mess this goo that somebody at some point thought look like cheese and I'm not sure how they came up with that conclusion but it kind of stuck and so we call this caseous necrosis and caseous literally refers to cheese and this is the same kind of cheese that might go on your crackers so cheese and you can think of it almost like cheesy death I guess cheesy deaths for the necrosis part I think I add an extra either by accident let me just fix that little - so cheesy deaths and because I'm naming things let me go ahead and give you a couple more names go and focus what the heck does that mean go and focus actually named after a doctor going but going focus is what we call this thing so it's termed a granuloma and specifically here because this granuloma which is the more broad term is in the sub pleural space we said and it's close to a fissure and we suspect it's from TB we would call it a go in focus actually it's the other name for it and both of these if you were to try to name both of these together the lymph node that has a granuloma and the go and focus together make up what we call the Gaon complex going complex so that just refers to both of the areas of disease so this is how disease starts but what happens after time passes let me actually just slide this over a little bit if we then take a little bit of passage of time and let's say there are three options right time has passed what are the different possibilities well let me actually go through and talk about micro bacterium Mycobacterium tuberculosis from the standpoint of the bug what is going on now she I just notice I have in the past made the mistake of using a capital T but it should be a lowercase T so Mycobacterium tuberculosis three options one option is that the bacterium may be dead you may have killed it with your macrophages another option is that the bacterium is dormant is just kind of lying in wait and the third option is that it's multiplying like crazy it's actually going and dividing and dividing and dividing and the last one actually is going to look if you looked on a chest x-ray like this you see lots of disease this red indicates diseased tissue not normal tissue and you might even see some large diseased lymph nodes so that's what it would look like on a chest x-ray and these other two on a chest x-ray basically would look normal so if you were to look on a chest x-ray this is what the three options would look like the first two would look normal and the third one that would look like like something is wrong and actually this is helpful because remember these two together we call these both situations we call them latent TB infection remember we can't really easily distinguish the two because in both situations you've had prior exposure to TB and in both situation the x-ray looks normal but if you had some super ability to actually zoom in let's say you could look under a microscope you would notice one key difference between these two and this is not something you can see on a chest x-ray but you could see only kind of if you had amazing vision you can look down at the microscopic level at somebody's lungs you'd see macrophage is and in the top case where there are dead bacteria the macrophages would look healthy and happy and in the case where you have dormant bacteria you would actually see some bacteria there some red live bacteria so that's the key difference between these two situations but again both of them we call latent TB infection and this scenario the bottom is going to be called progressive because things are slowly but surely getting worse you can see more disease on the chest x-ray primary with a one a degree sign infection this is the name for this progressive primary infection so it sounds a lot like what we had named out here with primary infection but the word progressive tells us that things are actually getting worse the disease is getting more nasty now let's actually play out the rest of this let's think about what will happen with the dormant situation I wrote out drew this out earlier and let's say more time is passing of course maybe years have gone by and this person has had live bacteria in their lungs for years and years nothing has happened and now they have what we call reactivation and maybe it's because their immune system is not working properly or maybe they have another disease who knows why but all of a sudden now the bacteria the TB bacteria are going to come out with a vengeance and there's going to be a cavity that forms usually in the upper lobes cavity that forms up here and it's going to be packed full of TB bacteria so this person you can imagine if they COFF they're going to be coughing out lots and lots of these little bacteria that I'm drawing and around that area there's a lot of disease so a lot of disease in this area and it's a very very distinct so if you see cavities and you see lots and lots of disease you're really going to be worried that this person might have what we call progressive progressive secondary infection and the reason I'm saying secondary is because again this is happening separate from that primary infection this is happening sometimes years later another way you can actually have this happened is through what we call secondary infection so maybe you actually literally get more TB maybe you're on a bus or a boat and a second person decides to cough and TB gets into your lungs through breathing it in that's another way to actually get progressive secondary infection so you can also think this is reinfection because you basically got re infected with the same bug right so the thing that ties reactivation together with reinfection is that in both situations your immune system has at some point in the past been exposed to TB and we think that's the main reason why you see these cavities and you see so much disease that's a really horrible infection to get so thinking about this a little bit more broadly then both the progressive primary infection and the progressive secondary infection who are the folks that you'd be most worried getting these diseases well I always worry about HIV patients before any other group because we know that HIV and TB is a really really bad combination they're at high risk for getting progressive disease both primary which is at the time they got the first infection with TB or secondary which could be years later