Flow through the heart Learn how blood flows through the heart, and understand the difference between systemic and pulmonary blood flow. Rishi is a pediatric infectious disease physician and works at Khan Academy.
Flow through the heart
- So what you're looking at is
- one of the most amazing organs in your body. This is the human heart.
- And it's shown with all the vessels on it and you can see
- the vessels coming into and out of it
- but the heart at its core is a pump and this pump is why we
- call it one of the hardest working organs in your body, because the heart starts pumping
- blood from the point where you're a little fetus and you're eight weeks old
- all the way until the point when you die. So this
- organ I think it will be really cool to look at it in detail
- but it's hard to do that looking just at the outside, so what did is I actually drew
- what it might look like at the inside.
- So let me just show you that now and it will follow
- the path of blood through the heart using this diagram
- Let me start with the little picture in the corner
- so let's say we have a person here
- this is teir face, this is their neck and I'm gonna draw their arms
- and they have in the middle of their chest their heart.
- SO the whole goal was to make sure that blood from all parts of the body, including their legs
- will make its way back to the heart first of all and then get pumped back
- out to the body. So blood is gonna come out from this arm
- let's say dumped into the air and the same on this side,
- and it's gonna come from their head and all three sources
- two arms and a head are gonna come together into one big vein
- And that's gonna be dumping into the top of the heart. And then separately you have veins from the legs.
- Meaning veins from the belly. Coming into another opening into the heart.
- So that's how the blood gets back to the heart. And anytime I mention the word vein, I just want to make sure you think of blood going towards the heart.
- Now If blood is going towards the heart, after the blood is pumped by the heart, it´s gonna have to go out to the heart.
- Right it´s gonna have to go away from the heart. So that´s the aorta.
- The aorta actually has the little arch like that. We call that the aortic arch.
- And it sends off one vessel to the arm, one vessel up this way, the vessel over this way and then this arch gonna go down and splits like that.
- So this is kind of simplified version of it.
- You can see how there are definetely some parallels between how the veins and arteries are set up.
- And arteries or anytime I mention the word artery, I want you to think about the blood going away from the heart.
- And easy way to remember that is that both start with the letter "A".
- So going to the big diagram we can see that blood´s coming this way and blood´s coming this way is ending up with the same spot.
- It´s going to end up at the, maybe I should draw it here, it´s ending up with the right atrium.
- That´s just the name of the chamber where the blood ends up in.
- And it came up in the right atrium from a giant vessel up top called the superior vena cava.
- And this is a vein of course because it´s bringing blood towards the heart.
- And down here the inferior vena cava.
- So these are the two direction the blood is going to be flowing.
- And once the blood is in right atrium, it´s going to head down into the right ventricle.
- So this is the right ventricle, down here.
- This is the second chamber of the heart.
- And it gets there by passing through the valve.
- And this valve and all valves in the heart are basically there to keep blood moving in the right direction.
- So it doesn't go to backwards direction.
- So this valve is called the Tricuspid valve.
- And it´s called that because it´s basically got three little flaps. That´s why they call it tri-.
- And I know you can only see two in my drawing and that´s just because my drawing is not perfect.
- And it´s hard to show kind of flap coming out of juby you can imagine it.
- So blood goes into the rigt verticle and where it goes next.
- Well after that it´s gonna go this way: it´s going to go to this vessel and it´s gonna split.
- But before it goes it has to passed another valve.
- So this is a valve right here.
- Call it Pulmonary valve.
- And it gives you the clue where the things we are going to go next.
- Because the word pulmonary means lungs.
- And so if this is my lung on this side. This is my left lung.
- And this is my right lung on this side.
- Then these vessels and all that they trying to get will be called, these vessels, this will be my, make sure I get my right and left straight, this is my left pulmonary artery.
- And I hesitated there just to make sure I got that because it´s taking blood away from the heart.
- And this is my right pulmonary artery.
- So this is my right and left pulmonary artery.
- As the blood goes down into my lungs, right. these the lungs that kind of nessel into my thorax, where my heart is sitting, goes into my lungs
- and remember this blood is blue.
- Why is it blue? Well,it´s blue because it doesn´t have very much oxygen.
- So one thing that I need to pick up is oxygen.
- So that´s one thing what the lungs gonna help me pick up and I´m gonna write O2 for oxygen.
- An it´s also blue and that reminds us that it´s full of carbondioxides, full of wastes.
- Because it´s coming from the body.
- Well the body made a lot of carbondioxides that it's trying to get rid of.
- So in the lungs you get rid of the carbondioxides and you pick up oxygen.
- So that´s why I switch it in this point blue colored vessel to red colored vessel.
- So now blood comes back this way and this way and dumps into this chamber.
- So what is that - that is our left atrium.
- So just like our right atrium we have one on the left.
- And it goes down into, you can probably guess how this one is called, is our left ventricle.
- So just like before where we went from the right atrium to the right vertricle, now we´re going from the left atrium to the left ventricle.
- And it passed through the valve here. So this valve is called the Mitral valve.
- And it´s job is of course to make sure the blood does not go from the left ventricle back to the left atrium by accident.
- Wants to make sure there is forward flows.
- And then the final valve, I need to find a nice spot to write it maybe to right here, this final valve that passes through is called the Aortic valve.
- And the Arotic valve is going to be what divides the left ventricle from this giant vessel that we talked about earlier.
- And this is of course the aorta. This is my aorta.
- So now blood is gonna go through the aorta to the rest of the body.
- So you can see how blood now flows from the body into the four chambers.
- The first into the right atrium. This is chamber number one.
- And then it goes into the right ventricle. This is chamber number two.
- It goes to the lungs and then back up to the left atrium. So this is chamber number three.
- And then the left ventricle.
- And this happens every moment of every day, everytime you heard your heart beating, this process is going on.
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