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Current time:0:00Total duration:11:51

Video transcript

so the job of our lungs in a pretty general level is to take blood that's without oxygen that our bodies have used up so I'm going to use blue here to represent that to take that blood and put oxygen in it and it comes out as oxygenated which is red blood I mean blood without oxygen gets a little darker that's why conventionally we think of it as blue versus red and from there the heart pumps this blood to the rest of the body so in a nutshell that's what the lungs do and to do that they grab oxygen from the atmosphere and take the carbon dioxide from the blood and blow it out co2 carbon dioxide and this exchange really is the full picture of what you do with every breath now in terms of how the lungs do this let's talk about the structure first for a bit I think it looks kind of like an upside down tree just because all these branches keep getting smaller and smaller as we reach the terminal branches I mean there's 20 or 30 levels here I can't draw them all but you get the idea they keep branching off and at the end we reach these units called alveoli let me write that word for you Elvia lie which is plural for alveolus and what that is is essentially an air sac let's blow that up down here so the alveolus looks kind of like a bulb is it air sac has very thin walls and lying along the walls almost almost in contact but not quite is the blood supply this is how things get from our blood to their lungs and back and forth so I'm going to draw a blue here to begin with because there's no oxygen to begin with as it travels and that the air goes back and forth between the blood supply and the alveolus it becomes red as it leaves because there's oxygen you can think of it as you know inhale oxygen goes in from here goes to the blood supply makes your exhale the carbon dioxide is going the opposite way and we exhale it can just leave the lungs and now the reason this exchange takes place is just a simple loss of air pressure in physics so if there's more oxygen in here relatively more compared to the blood supply then the oxygen wants to escape to the blood supply and if there's relatively more carbon dioxide in the blood then it also wants to escape to where there's less of it which is into the air sac so conveniently this allows us to take what we want and get rid of where don't want anymore okay so there's your bird eye view of how the lungs work in a nutshell and there are a lot of problems that can arise in this whole system but I think a better way to understand it is to break it down by the different players the different areas that can go wrong so we can think of lung problems as categories now the first woman the first problem I can think of is oxygen not coming in and so on the flipside of that number two would be carbon dioxide not escaping or to keep going let's go further into the lungs here at the alveolus I would say number three is something going on with this exchange process where between the air sac and the blood supply something is not working there so that's number three that's exchange and lastly if something is wrong with the blood supply blood cannot get to the lungs and come out that would be number four so I think these are the four big categories of lung diseases and let's go through them one by one now problems number one and two here we actually think of them as a pair of diseases there's restrictive and obstructive let's start with restrictive and this just describes the fact that the lungs which are supposed to expand when you take air in to make room for the air for some reason it's not expanding properly so this is an intake inspiration problem and since oxygen is the main point of taking air in in restrictive diseases we lack oxygen so what happens is the lungs for a variety of reasons becomes stiff and hard to blow up like a balloon that's been dipped in paper mache and it can't blow up properly so if you look at if this is supposed to be the size of the lung when it's blown up this smaller lung herein restrictive disease gives us a lot of wasted space all the space that could have had oxygen but is now not usable that just makes the whole system less efficient right so there's something wrong with the actual structure of the lungs that's making it hard to expand so let's think of some examples so there's fibrosis fibrosis just means laying down too much scar tissue so if the lungs are chronically injured or sometimes there's a genetic factor to it the tissue gets stiff just like a scar you would have on your hands except you have it all over your lungs so it's not no longer expandable there are also things that can affect the chest wall say if there's a muscular diseases that make it hard for the chest expand that also limits how big the lungs can get or sometimes there could be things that are deposited in the actual tissue of the lungs I can think of amyloidosis which is these protein particles that get studded into the lungs making it harder to expand so those are our examples of restrictive disease oxygen oxygen cannot get in now it's evil twin I guess they're both evil but its counterpart would be obstructive disease obstructive so if we said before that restrictive is about not getting air in then the opposite would be not getting air out in restricted diseases we're having trouble with expiration so instead of letting the lungs collapse back to its normal size at the end of an exhale it stays expanded like this let me just draw some of the branches here just to show you there are different reasons that obstructive diseases can occur sometimes let's say there's a mucous plug and air can get out or sometimes this Airways collapsed because the walls have lost its elastic quality structure so the area is essentially stuck in there let's think of all this extra air imagine how difficult it would be if you cannot exhale that's very uncomfortable so obstructive disease describes these large overinflated lungs now some examples would be something you've probably heard of as COPD which is actually a group of two different diseases one is emphysema which have to do with the lungs losing their elastic quality and the other one is chronic bronchitis which is just a lot of irritation day in and day out that makes a lot of mucus both of these result in these large inflated lungs something more common that a lot of people have is asthma which is when the Airways spasm and they close up blocking the air from getting out so restrictive and obstructive diseases kind of have to do with the global picture of the lung not to get into too much of the detail just think of restrictive as having trouble getting air in oxygen in and obstructive having trouble getting carbon dioxide out with the exhale so now let's zoom back into the alveoli what's going on down here that could give us lung disease so number three I said there's something wrong with exchange so let me just redraw this here we have our air sac so air has finally made it here to where it can make contact with the blood supply and one thing that we really mess up this process is let's say if this air sac is filled with fluid like that let's fill that in to make it yeah like that okay so what would happen to your oxygen so it's coming in here it wants to get to the blood and uh-oh it's stuck as you know it's much harder for air to diffuse through liquid than it is when it's empty space and then on the other hand carbon dioxide is here trying to get out and oh it's stuck in the fluid too so as you see this makes the whole exchange much less efficient so you have less oxygen going in and less carbon dioxide going out so that when I would say that this blue let's extend this a little further instead of turning red we're supposed to since it's so inefficient it eventually becomes this kind of weak red when it leaves so you have less oxygen in your blood and more to carbon dioxide than you would in a healthy lung so what could cause this to happen with the fluid one thing that's very common is an infection such as pneumonia see when our lungs are not doing well there's a lot of secretions mucus just fluid trying to flush out wash out what's there so pneumonia if there's bacteria or virus this fluid happens there's also edema edema kind of is just a general word for fluid being where it's not supposed to being pushed out so for some reason if there's too much blood in the blood supply let's say if your heart is not working well and all this blood is backed up then it will flow into the air sac where it does not belong and give us this picture of a wet inefficient lung then usually the lungs work best when they're dry because we're talking about air exchange here oh and I forgot to write a name for this category let's call this ventilation we're talking about the exchange here but ventilation technically means getting carbon dioxide out of here but I want to use this word to just describe the process of exchanging one gas for the other which is not working well here and talking about what versus dry lungs here kind of goes nicely into our fourth point so our fourth problem let's call it a problem with perfusion so it's it's funny it's kind of like the lungs are too dry so perfusion is the ability to get blood where it's supposed to go again let's draw our little alveolus singular it's alveolus so we have our blood supply coming in as usual and uh sometimes there can be a clot so our body can make clots and they can break off and float in the blood stream when they get to a place that's small enough to get stuck they get stuck here and stops the blood from flowing past this point so for the rest of the path there is no blood and the branches of blood supply that branches off past this point are also gone so as you can see in this scenario no matter how much oxygen we have in here we only have we don't have any blood supply to put it into so not having enough perfusion is a huge problem and we call it a pulmonary embolus so pulmonary means it's in the lungs in Villisca scribes a clot that forms somewhere else and it's traveled and if it gets lodged in the lungs and it's a pulmonary embolus now the severity of this really has to do with where in the blood supply gets stuck so let me just go back here up here and draw some blood vessels along these trees so if this embolus is all the way up here at a major branch and it shuts off this whole part of the lung then you have a huge problem people can die from this now if it's a very small branch like down here then it's still uncomfortable and you'll lose a portion of the lungs but it's not relatively not as big of a problem of course it will still compromise how well your lungs are working how much oxygen is getting in so on and so forth so here you have four very general categories of lung disease that I think provides a nice structure for okay what are the different players involved and what can go wrong to give us lung disease