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学习血液如何流经心脏,认识全身血与肺血的区别。里希是一名儿科传染病医师,是可汗学院团队一员。 Rishi Desai 创建




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 it and out of it but the heart at its core is a pump and this pump is is why we call it the hardest working organ in our body because it starts pumping blood from the point where you're a little fetus maybe about eight weeks old all the way until the point where you die and so this organ I think it'd be really cool to look at a little bit more detail but it's hard to do that looking just at the outside so what I did is I actually drew what it might look like on the inside so let me as you just show you that now and we'll follow the path of blood through the heart using this diagram let me start with with a little picture in the corner so let's say we have a person here and this is our face and this is our neck I'm gonna draw their arms and they have in the middle of their chest their heart and so the whole goal is to make sure that blood from all parts of their body including their legs can make its way back to the heart first of all and then get pumped back out to the body so blood is gonna come up from this arm let's say and dump into there and the same on this side and it's going to come from their head and all three sources the two arms and the 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've got veins from the legs meeting up with veins from the belly coming in to 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 you to make sure you think of blood going towards the heart towards the heart now if blood is going towards the heart then 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 and the aorta actually has a little arched like that and we call it the aortic arch and it sends off one vessel to the arm one vessel up this a vessel over this way and then this arch kind of goes down down down and splits like that so this is kind of a simplified version of it but you can see how there are definitely some parallels between how the veins and the arteries are set up and arteries so anytime I mention the word artery I want you to think of blood going away from the heart an easy way to remember that is that they both start with a letter A so going to our big diagram now we can see that blood coming in this way and blood coming in this way is ending up at the same spot it's going to end up at the actually and maybe I'll draw it here is ending up at the right atrium right atrium that's just the name of the chamber that the blood ends up in and it came into 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 inferior vena cava so these are the two directions that blood is going to be flowing and once blood is in the 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 a 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 in the backwards direction so this valve is called the tricuspid valve tricuspid valve and it's called that because it's basically got three little flaps that's why they call it try and I know you can only see two in my drawing and that's that's just because my drawing is not perfect and it's hard to show kind of a flap coming out at you but you can imagine it so blood goes into the right ventricle and where does it go next well after that it's going to go this way it's gonna go into this vessel and it's gonna split but before it goes there has to pass through another valve so this is a valve right here called the pulmonary valve pulmonary valves and it gives you a clue as to where things we're gonna go now right 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 I'll let you try to guess what they would be called these vessels this would be my make sure I get my right and left straight this is my left pulmonary pulmonary artery and I hesitated there just to make sure you got that because it's taking blood away from the heart and this is my right pulmonary pulmonary artery so this is my right and left pulmonary artery and so blood goes now into my lungs right these are the lungs that are kind of nestled 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 and so one thing that I need to pick up is oxygen and so that's one thing that the lungs are gonna help me pick up and I'm gonna write Oh two for oxygen and it's also blue and that reminds us that it's full of carbon dioxide it's full of waste because it's coming from the body right the body's made a lot of carbon dioxide that it's trying to get rid of so in the lungs you get rid of your carbon dioxide and you pick up oxygen so that's why I switch at this point from a blue colored vessel to a red colored vessel so now blood comes back in this way in this way and dumps into this chamber so what is that this is our left atrium our left atrium so just like our right atrium we have one on the left and it goes down into and you can probably guess what this one is called it's our left ventricle so just like before where it went from the right atrium to the right ventricle now we're going from the left atrium to the left ventricle and it passes through a valve here right so this valve is called the mitral valve mitral valve and it job is of course to make sure that blood does not go from the left ventricle back to the left atrium by accident it wants to make sure that there's forward flow and then the final valve and I have to find a nice spot to write it maybe right here this final valve that it passes through is called the aortic valve the aortic valve and the aortic 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 going to 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 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 out to the left atrium so this is chamber number three and then the left ventricle and this happens every moment of every day every time you hear your heart beating this process is going on