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The bronchial tree

Follow the path of an oxygen molecule as it makes its way from your mouth down to an alveolus! Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.

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  • blobby green style avatar for user Constance
    Does the warm and moist air help our body with anything?
    (19 votes)
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    • leafers ultimate style avatar for user Kieran Duncan
      I once went to a fancy hotel and spent 20 minutes (which was long enough) in a sauna (similar to a steam room). Very warm (over 50 Degrees Celsius), humid (over 80percent) small room. Steam rooms can be used for relaxation, general health, or to feel refreshed after a workout.
      The steam opens up the pores, increases the metabolism, elevates the heart rate, and the body begins to sweat. This can result in health benefits, especially when a steam room is used safely and frequently.

      "The warm, moist air increases the body's circulation and also loosens and relaxes muscles and joints. After a workout, a session in the steam room will help to keep the body relaxed and flexible, so that it will not lock up as a result of hard exercise. The steam room will also help the body eliminate toxins, forcing them out through the resulting sweat. The skin will be cleaner, softer, and healthier, especially if an exfoliating scrub is used in the steam room to remove the outer layer of dead skin.

      Steam rooms are also very helpful for people who suffer from asthma and respiratory conditions. The dry heat of a sauna is sometimes too intense for the lungs to handle, and the gentler moist heat of a steam room helps to relax and open up the lungs and bronchial tubes. In addition, a steam room can help to reduce joint pain and the symptoms of arthritis. After a session in a steam room, the bather usually feels more relaxed, which can help to reduce problems related to insomnia and poor sleeping." - this may be a load of rubbish, but it is what I read.

      On another note, think about the alveoli in our lungs? Our lungs are moist and warm for the diffusion of oxygen. If our lungs are already warm and moist, do you think that it would be better to put very dry air, or humid air into our lungs??
      (41 votes)
  • marcimus pink style avatar for user julia
    but does a piece of food go down the larynx cause when you showed the peanut it confused me
    (3 votes)
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    • duskpin seed style avatar for user tyrrelleslie
      There are a couple of things to say.(1 if a person has a Stroke they are advised not to eat and drink until they have seen a Speech Therapist who then does a sip test. Only then can the person perhaps take fluid that has the thickener added to it. this then stops liquid going into the lungs) (2 that plants give oxygen in the day and take in oxygen at night in the past our hospitals used to allow flowers at the bedside and remove them at night but now they do not allow any form of plants or flowers saying that they are bad for you)
      (2 votes)
  • aqualine ultimate style avatar for user Nate
    What is the trigger for the Epiglottis closing? Is the food or water causing a muscle to contract? some sort of nerve impulse? or is it just getting forced shut as food and water passes over it?
    (15 votes)
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    • leaf green style avatar for user Ezer500
      When swallowing, elevation of the hyoid bone draws the larynx upward; as a result, the epiglottis folds down to a more horizontal position, with its superior side functioning as part of the pharynx. In this manner it prevents food from going into the trachea and instead directs it to the esophagus, which is at the back
      (12 votes)
  • aqualine ultimate style avatar for user Tais Price
    if noes hair, and snot is used for filtering air then what is ear wax for? this might be off subject but I think it could be the same thing if its used for the same thing.
    (3 votes)
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  • piceratops ultimate style avatar for user Ari Mendelson
    I read somewhere that Tour de France champion Miguel Indurain was so great because he had much larger than average lungs. Do really big lungs really give an endurance athlete such a big advantage?
    (6 votes)
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    • male robot hal style avatar for user Austin Wiggins
      Not at all. Your lungs give you oxygen. The only difference would be that a person with large lungs would have to take fewer breaths than someone with smaller lungs. Really, you want to exercise, do cardio, and eat healthy to get your body in shape for athletic activities. Exercise and healthy foods are the real key to a body in good shape.
      (7 votes)
  • leaf green style avatar for user Richa Kumari
    Since our atmosphere is mostly nitrogen do we ever get some of it in us?
    (5 votes)
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  • winston default style avatar for user Byron
    Why don't out mouths have filters? Is there a good reason or just not really necessary?
    (5 votes)
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  • female robot ada style avatar for user Rachael
    At Rishi said if you swallowed something and it ended up in your lungs it would go towards the right lung because of gravity. How could something end up there, if there is a flap that closes and doesn't allow things to go that way? How does the flap know when something is to go to the lungs or to the trachea? And what would happen to the thing that ended up in your lungs? Would you still be able to breathe with that down there? Sorry for all the questions! I am very curious!!

    Thank You!!
    (5 votes)
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  • leaf green style avatar for user YJ
    we more susceptible to diseases if we breath through our mouths,
    so, as an weird evolutionary twist,is it better to have hairs in the back of our throats or not?
    (3 votes)
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    • leaf green style avatar for user Manushi V.
      We already have a slight amount of mucus in our throats, which is a little helpful. Yes, it would be helpful to have hair on the back of our throats to help prevent disease. The hair would prevent disease causing molecules, that have not already been filtered out, from entering our system.
      (4 votes)
  • blobby green style avatar for user salma
    so my book has different names for the lower respiratory tract and I'm confused cause i don't know where to put the names on the draw, I have (extrapulmonary bronchi- intrapulmonary bronchi-preterminal bronchioles - terminal bronchioles -respiratory bronchioles ) can you help me please.
    (4 votes)
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Video transcript

So here's a little person, and I've drawn their face, and you can see in blue at the bottom I've drawn their voice box, and I'm going to show you exactly what happens when you draw a little molecule like this of oxygen and to follow it along it's journey. So it's going to be breathed in either through the nose or through the mouth. And you know it's going to kind of end up in the same place or so we think, right? We said that basically kind of the back of the throat is where it's going to end up, and this is my nose kind of going in the back of the throat, and the mouth kind of empties into the same spot. But already, there are going to be some differences. So for example, you have in your nose, these little yellow nose hairs, and the first question, of course, people think of with nose hairs is what the heck is their purpose? What do they do? And nose hairs are part of our filter system, so we have this great filter system and there's nose hair, and their job is to make sure that all of the kind of large particles of dirt and dust are kind of picked up. So they're good for getting all the large particles out of the air so it's cleaned up. Then you also have this green slime, right? this kind of green mucus that we all kind of make, and this mucus sometimes, you think of it as snot, this snot or mucus is good for small particles, because it's really sticky, and this small particles of dust and dirt are going to glom onto it, and so that is our way of kind of cleaning up the air so that when we breathe in through our nose, the air is basically clean or at least cleaner than it would be otherwise. And so of course, if you compared nose air or the air that you breathe in through your nose to air that you breathe in through your mouth, the mouth air will be, of course a little dirtier, because they didn't have that nice filter system. And kind of thinking along the same route, if you think about picking your nose, that would be basically kind of cleaning the filter, right? So that's kind of a new way maybe of thinking about that habit. So air is going to end up going to the back of the throat. So air is going to kind of go in this way, and a little molecule of oxygen is going to kind of end up at the back of the throat. And another kind of interesting difference is that already, that oxygen molecule and the air around it is going to be slightly different in other ways. It's going to be cleaner if it went through the nose, but either way, nose or mouth, it's going to be warmer and also more moist. So that's another change. In comparison, on the outside, the air is a little colder and drier. So these are some key differences in terms of what's happening to the air. These are two major differences, right? So now the air or little molecule of oxygen has got a choice. It can either go kind of down one of two paths. One, I'm going to draw is going to be into the larynx. This is our larynx right here. And we also call our larynx our voice box, so you might remember that was the name I had mentioned previously, voice box, or larynx, is kind of the more medical word, I guess. And sitting over the larynx is the epiglottis. And the epiglottis is basically like a lid kind of protecting the larynx from making sure that food and water don't go into it. Now, there's another tube I just alluded to, and it's sitting right here, and this purple tube, is our esophagus So the esophagus is basically, it's fantastic for things like food and water. You want food and water to go down the esophagus because it's going to lead to the stomach. So you want food and water to go that way, but you don't want food and water to go into the larynx. And so you want to make sure that the epiglottis, that lid, is working really well. And if you're swallowing food and water, this epiglottis will literally just kind of close up and protect your larynx. But in this case, that's not happening. We're not actually food and water, we're a little molecule of oxygen, so let's follow that molecule a little bit further down. Let's see what happens to it. I'm going to drag up the canvas a little bit. Let's make a little bit of space, and I want to just stop it right there because I want to show you that the air molecule, the oxygen molecule has already kind of made an interesting crossroads. It's actually kind of broken an important boundary, and that's this boundary right here. And on the top of this boundary, I've included the larynx and of course, all the other stuff we just talked about-- the mouth and the nose-- and this is considered our upper respiratory tract. So anything above this dashed line is our upper respiratory tract, and then, of course, you can then guess that anything below the line must then be our lower respiratory tract. So this is an important boundary because people will talk about the upper and lower tract, and I want to make sure you know what is on which side. So on the top of it, is the larynx and everything above that, and below it is the trachea. Let me label that here. The trachea is right here, the wind pipe or the trachea, and everything below that, which, of course, mainly includes things like the lungs, but as we'll see a few other structures that we're going to name. So I'm going to keep moving down, but now you know that important boundary exists. So now let me just make a little bit more space you can see the entire lungs. You can see the molecule is going to go through the trachea, and actually, I have my left lung incompletely drawn. Let me just finish it off right there. So we have our right and left lung, right? These are the two lungs, and our air is going to just kind of slowly pass down-- our molecule of oxygen is going to pass down, and it's going to go either into the right lung or the left lung. Now here, I want to make sure I just take a quick pause and show you the naming structure. And the important word of the day is the bronchi, which alludes to one, or-- sorry, I screwed it up already-- the bronchi, which alludes to more than one-- sorry about that-- and bronchus, which alludes to one. So bronchi means more than one and bronchus means one. So just keep track of these letters, I and U-S. So if we say that, for example, we are going into this area right here. Let me just choose a new color so it's really clear. This will be our main. If we go into this spot-- let's say our air molecule or our oxygen molecule goes this way-- then we would say it's in our left main-- I'm just going to underline as I go-- left main bronchus. That's what we'd call that. And then if it went further, let's say it went down here, then instead of calling it main, I would call it the lobar. That's the word here. So I'd say it's my left lobar bronchus. And then if I wanted to go a little bit further, I could say well now this is my segmental, segmental. So these are the words that we use, and this final one would be then my left segmental bronchus. And of course, if we want to talk about two of them, let's say I want to talk about both this guy and this guy, then I would say those are my right segmental bronchi, because now I have to use the top word because it's plural. So that's the naming structure. And another kind of important naming structure you'll sometimes see is primary bronchus, secondary bronchus, and segmental, they call tertiary bronchus. So you'll see either one of those, but I'm going to stick to main, lobar, and segmental because I think it's a little bit easier and more intuitive to remember it that way. Now, there are a couple of important, interesting things happening already. So right here, this notch or this point right here, this is our carina. This is our carina. So at the carina, you have your break between the right and left main bronchus. And what I want to point out to you is that this is a little bit more vertical. This right-sided one is a little bit more vertical, and the left-sided one is a little bit more lateral. This is a little bit more flat, or lateral. So it's kind of a cool thing to know, which is that if something was to slide down the throat, let's say a penny or a peanut or something was to slide down here, it's more likely to go down this way simply because of gravity. So gravity is going to push things towards the right main bronchus more than the left main bronchus because the right main bronchus is a little bit more vertical. This is kind of a fun fact that you now know. And actually, I guess I didn't do this already, but we should actually take a break and make sure we name some of these things. Remember this is called our cardiac notch, and remember that's one clue to kind of telling apart the left and right lung. And the other clue we said was the lobes, so of course, the right one has the upper lobe, the middle lobe, and the lower lobe, and the left lung only has the upper and lower. So that's an important clue. I just want to make sure we don't forget our little tricks that we've learned for telling apart the lungs. So I'm going to take a little pause there, and now, I'm going to show you in a sped up version all of the different branch points. So for example, here we have just a couple of branch points, one, two, and getting into this segmental bronchi would be the third branch point. But I'm going to speed things along and show you how many more branch points there actually are before we get to the final part of our lung where the gas exchange actually happens, so enjoy. [MUSIC - NIKOLAI RIMSKY-KORSAKOV, "FLIGHT OF THE BUMBLEBEE"] Going back to the very point where we left off, we start with kind of a bronchi, and we said that there is a naming structure for how to name the bronchi, but that's really just the first three branches. And then after the first three branches, all of the orange stuff, all those branches going from branch point 4 all the way down to about branch point 20, those are the conducting bronchioles. So that's the name we give them. They're no longer bronchi, they're bronchioles. And so if you see that word just keep that in mind, that we're a little bit further along in the lungs. And then after the conducting bronchioles, you get into a few more branch points, and we call them the respiratory bronchioles. And actually the final I should mention this the final conducting bronchiole, sometimes you'll see this called the terminal bronchiole. It's that kind of a bad name because terminal sounds like we're done, but actually we're just done with the conducting bronchioles, and we're still kind of going into the respiratory bronchioles. I guess if I'm only point to one, I should just probably make it singular. And then finally, we get into the alveolar ducts and the alveolar sac, which is kind of a few alveoli put together. And if it's plural as alveoli, then singular just talking about one little part of that sac would be alveolus. So that's where our little molecule of oxygen ends up, and this is kind of where it ends up before it's going to participate in gas exchange. Now, this entire area, going from respiratory bronchioles on downwards, this is all called the respiratory zone, and anything above that is considered the conducting zone, so anything above that. And that really includes not just the connecting bronchioles, but conducting bronchioles, and then all the stuff above it. So all the bronchi and even the larynx and the mouth and the throat, that's all considered part of the conducting zone. So basically, oxygen is going to come in through the entire conducting zone, everything we just talked about, and it's going to go down into the respiratory zone, and finally our little molecule of oxygen is going to be very happy to finally have made it to the very end of the bronchial tree and is ready for gas exchange now.