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每次你呼吸时,氧气都会被带进肺部.现在就随我展开这段探索之旅!里希(Dr.RIshi Desai)是儿童传染病医师,他是可汗学院的成员之一. Rishi Desai 创建




let's say that this is you you're enjoying a nice sunny day and you decided to take a nice long deep breath of air and of course when I say air the part that you probably care the most about is just the oxygen part of that air right that's the part that we as humans need to survive so you take a deep breath and let's say that you take it through your mouth you take a deep breath through your mouth and then let's say you take one more deep breath a second deep breath and you take that one through your nose now you might think well these are two totally different ways of getting in air right that's certainly how it looks when you look at a mouth and a nose it doesn't look like they have much in common but the truth is that actually if you followed the air it almost follows an identical path right so the air is gonna go into the back of the throat really regardless of how you took it in so here we have air coming in from the nose and here you have air coming in from the mouth and they meet up in the back of the throat and then they go down down down they go towards this thing that we call the Adam's apple I'm going to bring up a little bit of the the canvas so you can see it more easily but basically you bring up this here you see this Adam's apple right here and after you can go ahead and take a feel of your own atoms after the Apple it's a pretty cool structure in the middle of your throat and everybody has it that's the first thing I want to tell you is that everybody has it not just men women have it too and the reason it's called an Adam's apple it's called an Adam's apple because Adam is a is a generally a boy's name and so it's to remind us that usually men or boys have larger Adam's apples than girls and if you're if you're trying to find it I should also want to point out there's this notch here and if you can feel the notch with your fingers that gives you a nice clues to where it's located but this is this is it this is the Adam's apple and what it does is it helps you control your voice and actually another name for the Adam's apple another name for it is sometimes people call it the voice box the voice box and of course Aaron's passing through the voice box and it's kind of the entryway into the trachea and so it actually allows me to make my vents really high or make my voice very low depending on how you change the muscles around in that Adam's apple so that's actually the the kind of first cool thing I want to point out to you is that you can actually control your voice I'm sure you knew this already but what you're using is your Adam's apple or your voice box now air keeps going right air is just gonna keep making its journey down and specifically of course the part of era I said you know we care about is the oxygen it's gonna keep making its journey down into the lung the area so this is now the lung area it's gone down the trachea and it goes into the two lungs the right and left lung this is the left lung I'm gonna put L for left and this is the right lung I'll put R for right and immediately you're thinking well wait a second aren't they switched now I want you to remember that this is from the perspective of the person who owns the lungs so that's why I'm putting left where I put it in right where I put it now we should probably go ahead and start labeling some of this you can see that the lungs actually don't look identical right they look slightly different for example this one has three lobes the right side has three lobes we call it the upper lobe middle lobe and lower lobe and the left one only has two lobes that's the first kind of big difference and the other difference is that you actually have this thing in the middle that we call a cardiac notch this thing right here this is called the cardiac notch and the reason we call it that is that it's a little spot that gets formed because the heart is literally kind of peeking out here and as a result it kind of makes a notch in the lungs when it develops so the heart takes up a little bit of space here this is our heart and as a result it takes or makes that notch so this is our heart space here so on the other side you've got of course your two lobes your upper and lower lobe and these are two clues so if you ever see a long just kind of sitting by itself and you want to figure out whether it's the left lung or the right lung you can look for the lobes the number of lobes or you can look for that cardiac notch now around here around these lungs you've got ribs right so you've got ribs here and between the ribs you've got rib muscles and then of course on both sides and below below the lungs and below the heart you've got a muscle a big muscle actually it's gonna come through here I'm gonna just kind of go through the word heart and it basically becomes the floor so the heart and the two lungs they sit on this floor made up of this muscle and this muscle is the diaphragm muscle so this diaphragm muscle makes up the floor the ribs make up the walls so what do we have we have basically a room we have a giant room with walls and a floor and this entire room we actually call the thorax so within this room then you have your two lungs in your heart so so far so good but I haven't done a very nice job of actually showing you where the air goes I've just kind of pointed that it goes to the two lungs but you don't have to get to see where it goes after that so let me actually I'm gonna erase a lot of this I'm gonna reveal to you what it would look like if you could slip on some x-ray glasses and look at your two lungs this is kind of what it would look like right you've got all this interesting architecture and the easiest way to kind of think about this probably the simplest way to think about this is to imagine a tree so imagine a tree and that tree has been flipped upside down so you've got all these branches off that tree and they're branching and branching and if you flip this tree upside down you start seeing that it looks a lot like what we have in our lungs our lungs basically look like a flipped up or flips it upside down tree and we even call it that we even call this entire structure we call it a bra kill tree so when you look at the lungs and they look kind of messy or complicated just think of them as an upside-down bronchial tree and all of a sudden it'll it'll look much simpler with basically in the middle you've got this nice trunk right this is our trunk and then it starts kind of branching from there so air goes down this main trunk this trachea and then it kind of starts splitting up and each of these kind of colored regions the green region or the purple region serves a different lobe so this green region serves the lower lobe down here the purple serves the upper lobe and on this side you've got an upper a middle and a lower lobe now I know it looks a little bit strange because you've got some green branches and what should be the middle lobe like right here you've got some orange branches and what looks like the upper lobe like right there but what you have to remember and this is kind of tricky to do and just try to play with it in your head what you have to remember is that what you have is basically a three-dimensional lung so you have to imagine that we're only looking at it from the front side but of course that middle lobe does go back and if it went back then you'd make perfect sense why the orange branches are where they're at now let me continue the air journey because I want to make sure we finish it off so let's say we take a little branch like this right we expand it we keep you know going zooming into it zooming into a zooming into it until its microscopic you can't see with your eyes anymore but you could see it under a microscope it would look like this it would basically under a microscope it would look like a bunch of little sacs like this and these sacs we call these alveoli alveoli and the air actually kind of runs into the alveoli it has a dead end and then it comes back around and then you breathe it out so that's how breathing works in the air goes all the way in from your mouth down to the alveoli takes a u-turn and then goes back out but before it does that before it leaves very close to the alveoli is blood and let's say blood is coming this way and going that way and what will happen is that actually out of the or into the blood let's do that first we'll go oxygen oxygen will actually go into the blood and out of the blood will be waste so you'll have some carbon dioxide waste that your cells have been making and that waste actually then gets thrown back into the alveoli so now you can see how oxygen gets from the outside world gets breathed in through the lungs when you inhale gets down into the alveoli exchanges with the blood and then you exhale and let all that carbon dioxide out