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找到心脏的具体位置以及功能.里希(Dr. Rishi Desai)是一名儿科传染病医师,是可汗学院团队一员。 Rishi Desai 创建




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 so this is where the lungs this is the 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 person who owns this heart so this is their left and right which is the opposite of us if we're looking at it as the heart is actually sitting between the two lungs within this protective casing that the ribs are basically there to to keep all these important organs safe and then bit below them so if you draw this here or if I draw it you can see now that below all of 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 out at the gym but this muscle is called the diaphragm 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 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 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 ribcage 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 that your cell hanging out over here this is you and you can think about any kind 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 is to of course live and be happy and you've got nearby a little blood vessel in fact every cell in our body has a little blood vessel that's nearby and this toe cell is 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 right there in a sense they're 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 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 nearby really no flow is happening so I'll just write no flow so as the little cell little toe cells making waste that waste let's draw a little ball right here it's gonna start accumulating right you're gonna start collecting more and more of it since the blood is not really flowing and it might start kind of 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 flipside 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 cells 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 and 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 of a sudden all this 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 a sudden the cell is gonna be very very happy and is gonna 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 through 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 that's at its core this is exactly what the heart is doing it's an amazing pump pushing blood so that you have good blood flow and so I'm gonna write that out on the side it's kind of job number one these are the jobs of the heart right it's a 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 referring to the entire body so systemic when I say that word I just mean the entire body all of the cells in the body now exactly how that happens actually you can see on this on this picture so here you have a giant vein this is a vein and you have an artery here this is an artery and blood is actually going through the artery that way and is 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 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 a 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 gonna want some oxygen and it's gonna 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 back out to the body it actually sends the blood over to the lungs and it goes over to the left lung and 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 the pulmonary flow or something else well these vessels all of them together are called coronary vessels coronary vessels and so specifically you might hear about a coronary artery or coronary vein but together you can call them coronary blood vessels all either 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 and thousands of cells and those cells just like our toe cell that we drew out in the corner they also need oxygen nutrients and have waste so those cells are going to need blood vessels supplying them as well and 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 to serve the needs of cells then the coronary vessels fall under the systemic flow