0:02So what you're looking at is one of the most amazing organs0:05in your body.
0:06This is the human heart.
0:07And it's shown with all the vessels on it.
0:10And you can see the vessels coming into it and out of it.
0:14But the heart, at its core, is a pump.
0:16And this pump is why we call it the hardest working organ
0:20in our body.
0:20Because it starts pumping blood from the point where you're
0:24a little fetus, maybe about eight weeks old,
0:26all the way until the point where you die.
0:29And so this organ, I think, would
0:31be really cool to look at in a little bit more detail.
0:34But it's hard to do that looking just at the outside.
0:36So what I did is I actually drew what
0:39it might look like on the inside.
0:40So let me actually just show you that now.
0:43And we'll follow the path of blood
0:45through the heart using this diagram.
0:48Let me start with a little picture in the corner.
0:51So let's say we have a person here.
0:55And this is their face, and this is their neck.
0:57I'm going to draw their arms.
1:00And they have, in the middle of their chest, their heart.
1:05And so the whole goal is to make sure
1:06that blood from all parts of their body,
1:08including their legs, can make its way back
1:11to the heart, first of all, and then
1:13get pumped back out to the body.
1:15So blood is going to come up from this arm, let's say,
1:18and dump into there.
1:20And the same on this side.
1:21And it's going to come from their head.
1:23And all three sources, the two arms and the head,
1:26are going to come together into one big vein.
1:30And that's going to be dumping into the top of the heart.
1:34And then separately, you've got veins
1:36from the legs meeting up with veins from the belly,
1:39coming into another opening into the heart.
1:42So that's how the blood gets back to the heart.
1:44And any time I mention the word vein,
1:48I just want you to make sure you think
1:49of blood going towards the heart.
1:55Now if blood is going towards the heart,
1:57then after the blood is pumped by the heart,
2:00it's going to have to go out to the heart.
2:02It's going to have to go away from the heart.
2:04So that's the aorta.
2:06And the aorta actually has a little arch, like that.
2:08We call it the aortic arch.
2:10And it sends off one vessel to the arm, one vessel up
2:14this way, a vessel over this way.
2:17And then this arch kind of goes down, down, down
2:20and splits like that.
2:22So this is kind of a simplified version of it.
2:24But you can see how there are definitely
2:26some parallels between how the veins and the arteries
2:29are set up.
2:30And arteries, anytime I mention the word artery,
2:34I want you to think of blood going away from the heart.
2:37And an easy way to remember that is
2:39that they both start with the letter A.
2:41So going to our big diagram now.
2:43We can see that blood coming in this way and blood coming
2:47in this way is ending up at the same spot.
2:50It's going to end up at the-- actually,
2:52maybe I'll draw it here-- is ending up at the right atrium.
2:58That's just the name of the chamber
3:00that the blood ends up in.
3:02And it came into the right atrium from a giant vessel
3:06up top called the superior vena cava.
3:10And this is a vein, of course, because it's
3:12bringing blood towards the heart.
3:15And down here, the inferior vena cava.
3:21So these are the two directions that blood
3:23is going to be flowing.
3:25And once blood is in the right atrium,
3:26it's going to head down into the right ventricle.
3:29So this is the right ventricle, down here.
3:33This is the second chamber of the heart.
3:37And it gets there by passing through a valve.
3:40And this valve, and all valves in the heart,
3:43are basically there to keep blood
3:44moving in the right direction.
3:46So it doesn't go in the backwards direction.
3:49So this valve is called the tricuspid valve.
3:54And it's called that because it's basically
3:56got three little flaps.
3:58That's why they call it tri.
3:59And I know you can only see two in my drawing,
4:01and that's just because my drawing is not perfect.
4:04And it's hard to show a flap coming out at you,
4:07but you can imagine it.
4:09So blood goes into the right ventricle.
4:11And where does it go next?
4:13Well after that, it's going to go this way.
4:15It's going to go into this vessel,
4:17and it's going to split.
4:19But before it goes there, it has to pass through another valve.
4:22So this is a valve, right here, called the pulmonary valve.
4:26And it gives you a clue as to where
4:28things are going to go next.
4:29Right?
4:29Because the word pulmonary means lungs.
4:33And so, if this is my lung, on this side,
4:36this is my left lung.
4:37And this is my right lung, on this side.
4:43Then these vessels-- and I'll let
4:44you try to guess what they would be called-- these vessels.
4:48This would be my-- I want to make sure I get my right
4:50and left straight.
4:52This is my left pulmonary artery.
4:59And I hesitated there just to make
5:01sure you got that because it's taking blood away
5:04from the heart.
5:05And this is my right pulmonary artery.
5:11So this is my right and left pulmonary artery.
5:14And so blood goes, now, into my lungs.
5:16These are the lungs that are kind of nestled
5:18into my thorax, where my heart is sitting.
5:20It goes into my lungs.
5:22And remember, this blood is blue.
5:25Why is it blue?
5:26Well, it's blue because it doesn't have very much oxygen.
5:30And so one thing that I need to pick up is oxygen.
5:33And so that's one thing that the lungs
5:36are going to help me pick up.
5:38And I'm going to write O2 for oxygen.
5:41And it's also blue.
5:42And that reminds us that it's full of carbon dioxide.
5:45It's full of waste because it's coming from the body.
5:48And the body's made a lot of carbon dioxide
5:50that it's trying to get rid of.
5:52So in the lungs, you get rid of your carbon dioxide
5:54and you pick up oxygen.
5:56So that's why I switch, at this point,
5:59from a blue-colored vessel to a red-colored vessel.
6:03So now blood comes back in this way and this way and dumps
6:06into this chamber.
6:08So what is that?
6:09This is our left atrium.
6:14So just like our right atrium, we have one on the left.
6:18And it goes down into-- and you can probably
6:21guess what this one is called-- it's our left ventricle.
6:25So just like before, where it went from the right atrium
6:28to the right ventricle, now we're
6:30going from the left atrium to the left ventricle.
6:33And it passes through a valve here.
6:35So this valve is called the mitral valve.
6:41And its job is, of course, to make sure
•Current transcript segment:6:43that blood does not go from the left ventricle back
6:46to the left atrium by accident.
6:48It wants to make sure that there's forward flow.
6:52And then the final valve-- I have
6:54to find a nice spot to write it, maybe right here.
6:58This final valve that it passes through
7:01is called the aortic valve.
7:05And the aortic valve is going to be
7:08what divides the left ventricle from this giant vessel
7:13that we talked about earlier.
7:15And this is, of course, the aorta.
7:17This is my aorta.
7:20So now blood is going to go through the aorta
7:22to the rest of the body.
7:24So you can see how blood now flows from the body
7:27into the four chambers.
7:29First into the right atrium-- this is chamber number one.
7:33And then it goes into the right ventricle.
7:35This is chamber number two.
7:37It goes to the lungs and then back out to the left atrium.
7:40So this is chamber number three.
7:41And then the left ventricle.
7:43And this happens every moment of every day.
7:46Every time you hear your heart beating,
7:48this process is going on.