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Meet the lungs!

Breathing in through the mouth or nose, air travels down the throat, through the Adam's apple or voice box, and into the lungs. The lungs, which look like an upside-down tree, direct air to tiny sacs called alveoli. Oxygen from the air enters the bloodstream, while waste carbon dioxide exits into the alveoli and is exhaled. This process is vital for human survival. Created by Rishi Desai.

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  • piceratops sapling style avatar for user Ely
    How can the food travel down into our organs if the diaphram is beneath the heart and the lungs?
    (87 votes)
    • blobby green style avatar for user John O'Leary
      Food, after being chewed in the mouth, is swallowed and goes down the esophagus, which is a tube that runs parallel to the trachea. There is a junction where the larynx forks into the trachea and esophagus, but the trachea is closed off with the epiglottis while eating so that food and water don't fall into the lungs. The esophagus (which connects the larynx and stomach) runs behind the trachea, behind the lungs, and then through a hole in the diaphragm. Since the diaphragm marks the bottom of the thorax, the esophagus also runs into the abdomen, which contains the stomach and the rest of the GI tract.
      (201 votes)
  • leaf yellow style avatar for user Jacob Winters
    So I honestly don't where to put this question, so I decided to put it here because I'm pretty sure it has to do with the lungs/diaphragm.
    What is physically happening when we hiccup? Why do we do it?
    (17 votes)
  • blobby green style avatar for user narn2022
    The air we breath contains Nitrogen, Oxygen, Carbon dioxide, and some other gases, right? Now, the Carbon dioxide consists of 2 things - Oxygen and Carbon. When we breath in the CO2, does the body extract the oxygen from the carbon dioxide?
    (5 votes)
    Default Khan Academy avatar avatar for user
    • purple pi purple style avatar for user Jurre Moor
      Why would we do that when there is ready-to-use oxygen around in sufficient quantities ? As you stated the air we breath holds nitrogen(78%), oxygen(20%), carbondioxide(0.04%) and trace gases. So there is much more oxygen around then there is carbondioxide. And : breaking down carbondioxide consumes energy, i'd like to use that energy for other things ;-)
      (27 votes)
  • female robot amelia style avatar for user Thousif
    How does Cigarette smoking or tobacco affects our lungs and How does it cause cancer.
    (7 votes)
    Default Khan Academy avatar avatar for user
    • spunky sam blue style avatar for user Abdullah Yousuf
      Tobacco smoke contains more than 70 different cancer-causing substances. When you inhale smoke, these chemicals enter your lungs and spread around the rest of your body.
      Scientists have shown that these chemicals can damage DNA and change important genes. This causes cancer by making your cells grow and multiply out of control.
      (15 votes)
  • blobby green style avatar for user erikagiblin
    What causes the feeling of dread (when your heart "drops") to feel the way it does?
    (5 votes)
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    • male robot donald style avatar for user aarnav
      When you're in a stressful or nerve-wracking situation, your brain releases the stress hormones, cortisol and adrenaline. These open up your bloodstream and send lots of blood to your muscles and essential organs, like the heart. This causes your heart to suddenly palpitate, or to quickly change from your resting heart rate to a fast heart rate. This causes the "heart-dropping" feeling. Another thing that causes this is your diaphragm muscles to relax due to the heart beating so much.
      (19 votes)
  • aqualine ultimate style avatar for user Alyssa Brock
    Isn't the reason it's called an Adam's Apple is because in the Bible, Adam ate the Forbidden Apple?
    (10 votes)
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    • winston default style avatar for user David
      Apparently so... Although many may not believe, I have not the authority to impose on you your values and religion. More specifically, a piece of apple got stuck in his throat leaving a lump.

      Hope this helped! :)
      (5 votes)
  • aqualine ultimate style avatar for user Learning student
    About the Adam's apple thing, it says that "Adam" is a boy's name, and it is called the Adam's apple to remind us that boys/men have the Adam's apple too, but theirs is larger than girl's. But there are lots of boy names, why Adam of all names? Not saying that's a bad name though, it's a great name.
    (8 votes)
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    • male robot donald style avatar for user Tybalt
      The name originated in the 1600's, and most likely referred to the Adam found in Abrahamic religions (Adam and Eve, first man and woman). A 1662 text known as Bartholinus Anatomy (or Bartholin's Anatomy) states that the name came about due to a common belief at the time that a piece of the forbidden fruit got lodged into Adam's throat and stuck with men ever since.
      (9 votes)
  • blobby green style avatar for user Arbaaz Ibrahim
    Where are the alveoli located and how many of them are there?
    Why does the oxygen have to go into the blood before going out as carbon dioxide?
    (7 votes)
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    • leaf blue style avatar for user Esther Dickey
      The oxygen goes into the blood and is carried around the body to the cells, which use it and produce CO2 as a byproduct. The CO2 goes back into the blood which carries it back to the lungs, where it is exchanged for more oxygen.
      There are 300-500 million alveoli in the lungs.
      (7 votes)
  • aqualine seed style avatar for user SEAN
    What if you inhale pure oxygen
    (5 votes)
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  • male robot johnny style avatar for user Owen Cooney
    Where does the blood take the oxygen?
    (6 votes)
    Default Khan Academy avatar avatar for user

Video transcript

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. 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. 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 follow the air, it almost follows an identical path. So the air is going to 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 canvas so you can see it more easily. But basically, you see this Adam's apple right here. And actually you can go ahead and take a feel of your own Adam's 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 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 trying to find it, I just 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 clue as to where it's located. But 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, sometimes people call it the voice box. The voice box. And of course, air is passing through the voice box, and it's kind of the entryway into the trachea. And so it actually allows me to (FALSETTO) make my voice really high, (DEEP BARITONE) or make my voice very low, depending on how you change the muscles around in that Adam's apple. So that's actually 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. Air is just going to keep making its journey down-- and specifically, of course, the part of air I said we care about is the oxygen. It's going to keep making its journey down into the lung area. So this is now the lung area. It's going down the trachea, and it goes into the two lungs-- the right and left lung. This is the left lung. I'm going to 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? 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 and 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. 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. So 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 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 lung 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 number of lobes, or you can look for that cardiac notch. Now around these lungs, you've got ribs. So you've got ribs here, and between the ribs, you've got rib muscles. And they are, of course, on both sides. And below the lungs and below the heart, you've got a big muscle. Actually it's going to come through here. I'm going to 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 and your heart. 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 through the two lungs, but you don't actually get to see where it goes after that. So I'm going to erase a lot of this. I'm going to 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. You've got all this interesting architecture. And the easiest way to 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 upside down tree. And we even call it that. We even call this entire structure, we call it a bronchial 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 look much simpler. 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 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 in what should be the middle lobe, like right here. You've got some orange branches in 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-- is that what you have is basically a three-dimensional lung. So you have to imagine that we are 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 of 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, we expand it. We keep zooming into it, zooming into it, zooming into until it's microscopic. You can't see it with your eyes anymore, but you could see it under a microscope. It would look like this. It would basically, under a microscope, 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. The air goes all the way in through 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 into the blood will 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.