Meet the lungs

Every time you take a breath, oxygen makes it way into your lungs. Follow along on that journey! Rishi is a pediatric infectious disease physician and works at Khan Academy.

Lets say that this is you. Youre 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, thats the part that we as humans need to survive.

So you take a deep breath. Lets say you take it through your mouth,

you take a deep breath through your mouth.

And then lets say you take one more deep breath, a second deep breath,

and then you take that one through your nose.

And you might think, well,these are two totally different ways of getting in air,

thats certainly how it looks when you look at the mouth and nose,

they dont look like they have much in common.

But the truth is that actually if you follow the air,

it almost follows an identical path.

The air is going into the back of the throat really regardless of how you took it in.

So here we have air coming in from the nose,

in here yet air coming in from the mouth and they meet up in the back of throat.

And then they go down down down,
they go towards this thing that we call the Adams apple.

Im gonna bring it up a little bit, you can see it more easily.

But basically you bring up this, you see this Adams apple right there.

And actually you can go ahead and take a feel of you own Adams apple.

Its a pretty cool structure in the middle of your throat

and everybody has it, thats the first thing I want to tell you,

that everybody has it, not just in men, women have it too.

And the reason its called an Adams apple is because Adam is generally a boys name.

And so its to remind us that usually men or boys have larger Adams apples than girls.

And if youre trying to find it, I also want to point that its a notch here.

And you if you can feel the notch with your fingers,

in that case you have a nice clue as to where it is located.

This is Adams apple and what it does is, it helps you control your voice.

And actually theres another name for Adams apple.

Another name for it, sometimes people call it the voice box. The voice box.

And of course air passing through the voice box in this kind of the entry way into the trachea.

And so it actually allows me to make my voice very high or make my voice very low,

depending on how you change the muscles around in that Adams apple.

So thats actually kind of a first cool thing I want to point out to you, that you can actually control your voice.

Im sure you knew this already but what youre using is the Adams apple, your voice box.

Now air keeps going, air is just gonna keeps making its journey down and

specifically of course the part of air I said, you know, we care about is the oxygen.

Its gonna keep making its journey down into the lung areas,

now the lung areas, it's gone down the trachea and it goes into the two lungs, the right and left lungs.

This is the left lung, Im gonna put L for left and this is the right lung, Ill put R for right.

And immediately youll think, "Wait a second, arent they switched?"

Now I want you to remember that this is from the perspective of the person who owns the lungs.

So thats why I put it in left where I put it, in right where I put it.

Now we should probably go ahead and start labeling some of these.

You can see that the lungs actually dont look identical, right?

They look slightly different, for example, this one has three lobes.

The right side has three lobes called the upper lobe, middle lobe and lower lobe.

And the left one only has two lobes, thats the first kind of a 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 its a little spot that gets formed

because the heart is literally kind of peeking out here.

And as a result its kind of makes a notch in the lung where it develops.

So the heart takes a little space here, this is the heart.

And as a result, it takes or makes that notch. So this is our heart space there.

So on the other side youve got of course your two lobes, your upper and lower lobes.

And these are exclusive, you see a lung just kind of sitting by itself.

And you want to figure out whether its 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, youve got ribs.

Youve got ribs here and between the ribs youve got rib muscles and of course on both sides.

And below the lungs and below the heart, youve got a muscle, a big muscle.

Actually its gonna come through here, Im just gonna kind of go through the word heart,

and it basically becomes the floor.

So the heart and the two lungs sit on this floor that 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 the floor.

And this entire room we actually call the thorax.

So within this room then you have your two lungs and your heart.

So, so far so good, but I havent done a very nice job of actually showing you where the air goes.

I just kind of pointed that it goes to the two lungs, we dont have to get to see where it goes after that.

So let me actually, Im gonna erase a lot of these.

Im gonna reveal to you what it would look like if you could slip on some X-ray glasses

and look into your two lungs, this is kind of what it would look like.

Youve got all these 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,

to imagine a tree, and that tree has been flipped upside down,

so youve got all these branches of that tree and they are 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 a flipped upside down tree and we even call 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 messier and complicated.

Just think of them as an upside down bronchial tree and all of a sudden

itll look much simpler with basically in the middle youve got this nice trunk,

this is our trunk, and then its kind of branching from there.

So air goes down this main trunk, this trachea, and they kind of start splitting up.

And each of this kind of colored regions, the green region and the purple region serve 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

youve got some green branches in what should be the middle lobe like right here.

Youve got some orange branches in what looks like the upper lobe like right there.

But what you have to remember, this is kind of tricky, just try to play it in you head,

what you have to remember is that, what you have is basically a three dimensional lung.

So you have to imagine that we are literally looking at the front side

but of course that middle lobe does go back.

And if you went back then youd make perfect sense
why the orange branches are where they are at.

Now let me continue the air journey because I wanna make sure we finish it off.

So lets say we take a little branch like that, we expand it.

We keep zooming into it, zooming into it, zooming into it,

until its microscopic, you cant see it with your eyes anymore.

But you could see it under a microscope. It would look like this.

It would basically in a microscope, it would look like a bunch of little sacs like these.

And these sacs, we call these alveoli. Alveoli.

And the air, it 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 thats how breathing works.

The air goes all the way from the mouth down to the alveoli, takes a U-turn and it goes back out.

But before it does that, before it leaves, very close to the alveoli is blood.

Lets say blood is coming this way and going that way, and what will happen is that,

actually out of the or into the blood, lets do that first.

Weve got oxygen, oxygen will actually go into the blood, and out of the blood will be waste.

So youll 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 the oxygen gets from the outside world,

gets breathed into 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.