Meet the heart! Find out exactly where the heart rests in your body and what it does. Rishi is a pediatric infectious disease physician and works at Khan Academy.
Meet the heart!
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- I really like this picture that I found. It actually
- shows you really neatly where the heart sits in our body
- so you can see the heart is surrounded, on both sides, by ribs, right?
- And in fact, I didn't draw it in yet, but let me show you where the
- lungs would be. This is the right lung
- and on this side you'd have the left lung. So this is where
- your heart sits: between two lungs. And I'm saying
- left and right from the perspective of the the person who owns this
- heart. So this is their left and right, which is the opposite
- of us if we're looking at it. The heart is actually sitting between the two
- lungs within this protective casing that
- the ribs are basically there to keep all these important organs
- safe. And then below them, so if you draw
- this here. Or if I draw it, you can
- see now that below all this stuff is
- a really really important muscle. So this muscle
- people don't talk about this muscle, or this is not the kind of muscle
- that you usually see people working on at the gym, but this muscle is called the diaphragm.
- So your diaphragm muscle
- and your ribs are enclosing a space, right? The diaphragm becomes the floor, and the ribs are kind of the
- ceiling and the walls of this space.
- And if you look at the contents of this space, you'd have your lung
- and you'd have your heart. So, this entire space then
- is called your thorax.
- So what exactly does the heart do? Let's actually make a little bit of
- space now, and bring up a
- zoomed in version of the heart.
- Let me start by orienting you to the heart. This is our right lung
- and on the other side we have our left lung. And all this would be
- inside of the rib cage, but I'm not going to draw that now, because that would
- make it harder to see the heart itself. So to think
- about exactly what the heart does, I think one, kind of neat way to do it is
- to actually imagine that you're a cell. So put yourself in the perspective
- of a cell, and let's say you're a cell hanging out
- over here. This is you. And you can
- think about any part of the body that you could be. Let's say a little
- toe cell. So let's say you're a toe cell
- and your job, of course, is to live and be happy,and you've got
- near by, a little blood vessel. And in fact, every cell in our body
- has a little blood vessel that's near by. And this toe cell
- is just trying to make a living. And toe
- cells need certain things, right? They need, for example, let's say oxygen.
- I'll write it in white so it's very clear. They need oxygen
- and they need nutrients, right?
- So cells need certain things to live and be happy.
- And on the flip-side, they also make waste. They're in
- a sense just like us, they make waste. And that waste could be
- all sorts of things, and one that kind of jumps to mind is
- carbon dioxide (CO2). So carbon dioxide is waste
- for this cell. So it's making some
- waste and for the moment let's imagine that there's no blood flow.
- So, even though there's a blood vessel near by,
- really, no flow is happening, so I'll just write "no flow".
- So as the little cell
- makes waste. That waste, let's draw a little ball right here,
- it's going to start accumulating, you're going to start collecting more and more of it
- since the blood is not really flowing. And it might kind of
- end up getting all the way around our toe cell. So our toe cell is getting
- swamped, literally getting kind of covered by its own waste.
- And on the flip-side, is it getting oxygen or nutrients? No.
- It's not getting either of these things. So, before very
- long, I would say within minutes, our toe cell
- is thinking, "Well this is not a very happy way to live!" this is
- actually really very sad, this is awful. And if this continues
- the toe cell would die. So, what a toe
- cell needs, and what every cell needs, and that could be a finger cell or a
- skin cell, or really any cell that's living, needs
- flow. Right? It needs this blood to be flowing nicely
- and smoothly. And if there is flow
- then you get a very different picture, right? If there's flow then all the sudden all the
- waste product is actually now lifted and taken away.
- It's flowing away, and it's a little bit like having
- someone come by and pick up the trash, then you don't have trash all over the house.
- So then you have nice flow, and
- in return, oxygen and nutrients are delivered. So this stuff
- gets delivered as well. So, all of the sudden the cell is going to be
- very, very happy, and is going to be living just fine.
- So, really if you want all of the cells in your body to be living just fine
- like this cell here, you really want good flow throughout the
- body. And so this is really point number one. Is that you really
- need, somehow, to have blood flow moving and pushing
- blood constantly throught the body. So,
- to do this for billions and billions of cells you would need a pretty powerful
- pump, right? Something that's going to be able to pull
- in all the blood from the body, and then push it back out. And that's what the heart
- is. I mean at its core, that's exactly what the heart is doing.
- It's an amazing pump, pushing blood, so that
- you have good blood flow. And so I'm
- going to write that on the side as kind of job number one. These are the jobs of the heart.
- So jobs, and number one, would be
- blood flow. And I'll write systemic
- flow. Systemic flow. And all
- that systemic means is that I'm refering to the entire body. So systemic
- when I say that word, I just mean the entire body. All the cells
- in the body. Now, exactly how that happens actually
- you can see on this picture. So, here you have a giant
- vein, this is a vein, and you have an artery.
- This is an artery.
- And blood is actually going through the artery, that way.
- And it's actually coming into two veins, the one
- at the top, this is called the superior, superior just kind of means
- at the top. Superior vena cava. That's the
- name of the vein. And at the bottom here, you can't see it because
- it's on the other side of the heart, but there's another vein called the inferior vena cava.
- And these two veins, this is also a vein,
- these two veins are actually dragging blood in from all over the body,
- into the heart.
- And then, when the heart is ready to pump it back out, it goes into this
- artery, and the name of it is the aorta.
- So if you've heard of the aorta, this is the artery that people
- are talking about. So this is how blood comes and gets pumped
- around. But this isn't actually the only job of the heart. The job,
- the second job of the heart, is actually
- also in this picture, and it's called pulmonary flow.
- Pulmonary flow. So, what does that
- mean? Well, we know that cells are expecting
- oxygen, right? We know this. And that they have a lot of carbon dioxide
- waste. Well, it's good to move things around. It's good
- to move blood around. But if you actually never got rid of that carbon dioxide
- or brought in new oxygen, then a cell is not going to be very happy either.
- I mean, you can have blood flow, but at some point it's also going to want some oxygen.
- And it's going to want to get rid of that carbon dioxide. So, that's where the
- lungs come in. So what happens is that the heart, before
- sending blood out the aorta, before just dishing it out back into the body,
- it actually sends the blood over to the
- lungs. And it goes over to the left lung, and over to the right lung.
- And the blood comes back from the right lung
- and the left lung, and gets pushed back into
- the heart, and then gets squeezed through the aorta. So there's this
- actual extra little step here, where blood is going to
- and from the lungs, and that's the pulmonary flow.
- So the final thing you'll notice, if you look at this picture it's hard not to notice,
- is that there are these, kind of wriggly looking little
- blood vessels all over the heart. And what are these
- exactly? I mean, you've got red ones, and blue ones, and
- the blue ones are the veins, and the red ones are the arteries
- but are they part of the systemic flow, or pulmonary flow, or something else?
- Well, these vessels, all of them,
- together are called coronary vessels.
- And so specifically you might hear about
- a coronary artery, or a coronary vein, but together you can call them
- coronary blood vessels. I'll add the word blood here. So these
- coronary blood vessels are actually serving the heart muscle
- itself. I mean remember, the heart
- is made up of thousands and thousands, actually tens of thousands of cells
- and those cells, just like our toe cell that we drew,
- they also need oxygen, nutrients, and have waste.
- So, those cells are going to need blood vessels supplying
- them as well. So, that's what the coronary blood vessels are. They're literally
- the blood vessels that go to and serve
- the heart. So these are the ones that serve the heart.
- Now, if they're serving the heart muscles
- and the heart cells, then, think about it, would they fit under
- the systemic flow, or pulmonary flow? Well if the
- main job is to serve the needs of cells, then
- the coronary vessels fall under the systmic flow.
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