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循环系统及心脏简介. Sal Khan 创建




where I left off in the last video we talked about how the hemoglobin in red blood cells is what's ops up all of the oxygen so that it increases the diffusion gradient or it increases the incentive we could say for the oxygen to go across the membrane we know that the oxygen molecules don't know that that there's less oxygen here but if you watch the video on diffusion you know how that process happens if there's less concentration here than there the oxygen will diffuse across the membrane and there's less inside the plasma because the hemoglobin is sucking it all up like a sponge now one interesting question is why does a hemoglobin even have to reside within the red blood cells why don't they just why aren't hemoglobin proteins just freely floating in the blood plasma you know that seems more efficient you don't have to have things crossing through in and out of these red blood cell membranes you wouldn't have to make red blood cells what's the use of having these containers of hemoglobin it's actually a very interesting idea if you had all of the hemoglobin sitting in your blood plasma it would actually hurt the flow of the blood the blood would become more viscous or more thick it would become I don't want to say like syrup but it would become thicker than blood is right now and by packaging the hemoglobin inside these containers inside the red blood cells what it allows the blood to do is flow a lot better imagine if you wanted to put syrup in water if you just put syrup if you put syrup straight into water what's going to happen the water is gonna become a little syrupy a little bit more viscous and not flow as well so what's the solution if you wanted a transport syrup in water well you could put the syrup inside little containers or inside little beads and then let the beads flow in the water and then the water wouldn't be all gooey and that's exactly what's happening inside of our blood instead of having the hemoglobin sit in the plasma and make it gooey it's it's it's it's inside these beads that we call red blood cells that allows the flow to still be non viscous so I've been all zoomed in here on the alveolus and in these capillaries these pulmonary capillaries let's zoom out a little bit just to uh Nora zoom out lot just to understand how is the blood flowing and get a better understanding of pulmonary arteries and veins relative to the other arteries and veins that are in the body so here I copied this from Wikipedia this diagram of the human circulatory system and here in the back you can see the lungs let me let me do it in a nicer and a nice dark color so we have our lungs here drumwright like that those are lungs you can see the heart is sitting right in the middle and what we learned in the last few videos is that we have our little alveoli and our lungs remember we get to them from our bronchioles which are branching off from the bronchi which branch off from the trachea which connects to our larynx which connects to our pharynx which connects to our mouth the nose but anyway we have our little alveoli right there and then we have the capillaries the capillary so when we go away from the heart when we go from the way from the heart and we're gonna beat delve a little bit into the heart in this video as well so when blood travels away from the heart it's deoxygenated it's this blue color so this right here is blood this right here is blood traveling away from the heart it's going behind these two tubes right there so this is the blood going away from the heart so these this blue that I've just I've been highlighting just now this these are the pulmonary arteries so the pulmonary arteries and then they keep splitting into arterioles and all of that and eventually wears in capillaries super super small tubes they they run right past the alveoli and then they become oxygenated they become oxygenated and now we're talking we're going back to the heart so we're talking about pulmonary veins so we go back to the heart so these capillaries and the capillaries we get oxygen now we're gonna go back to the heart hope you can see what I'm doing and now we're going back to the heart and we're going to enter the heart on this side we're going to enter the heart right over you actually can't even see where we're entering the heart we're gonna enter the heart right over here and I'm going to go into more detail on that now we have oxygenated blood it's red and then that gets pumped out to the rest of the body now this is the interesting thing this is the interesting thing when we're talking about pulmonary arteries and veins remember the pulmonary artery was blue as we go away from the heart we have deoxygenated blood it's but it's still an artery then as we go towards the heart from the lungs we have a vein but it's oxygenated let me write that down I wrote that in the last video but pulmonary pulmonary so the pulmonary artery artery no oxygen or maybe I shouldn't write that I should write deoxygenated because there might be some oxygen deoxygenated and then the pulmonary vein it has oxygen it has oxygen so that's this little loop here that we start and I'm gonna I'm gonna keep going over the circulation pattern because the heart can get a little confusing especially because it's kind of three-dimensional nature but what we have is the heart pumps pumps deoxygenated blood from the right ventricle you're saying hey why is it the right ventricle that looks like the left side of the drawing but it's this dude's right hand side right this is this guy's right hand or this is his right hand and this is this dude's left hand he's looking at us right we don't care about our right and left we care about this guy's right and left and he is looking at us he's got some eyeballs and he's looking at us so this is his right ventricle actually let me just start off with the whole cycle so we have deoxygenated blood coming from the rest of the body right this is deoxygenated blood coming from the rest of the body right here this is actually the name for this big pipe is called the inferior vena cava inferior cuz coming up above below actually you have blood coming up from the arms and the head up here they're both meeting right here right here they meet here in the right in the right atrium let me label that and we're gonna I'm gonna do a big diagram of the heart in a second so it's the right atrium and why are they deoxygenated because this is blood returning from you know our legs if we're running or returning from our brain which needed that that had to use respiration or maybe we're working out and we're turning from our biceps but it's deoxygenated blood it shows up right here in the right atrium it's on our left but this guy's right hand side from the right atrium it gets pumped into the right ventricle it gets pumped into or it actually passively flows into the right ventricle the ventricles do all the pumping then the ventricle contracts and pumps this blood right here and you don't see it but it's going behind this part right here the right it goes from here through this pipe so you don't see it I'm gonna do it a detailed diagram in a second into the pulmonary artery we're going away from the heart this was a vein right this is a vein going going to the heart this is a vein inferior vena cava vena cava vein this is superior vena cava these are veins they're deoxygenated then I'm pumping this deoxygenated blood to away from the heart to the lungs now this deoxygenated blood this isn't an artery right this isn't pulmonary artery then it gets oxygenated and now it's a pulmonary vein and once it's oxygenated it shows up here in the left let me do a better color like than that it shows up right here in the left atrium atrium you can imagine you know it's kind of a room with a skylight or that's open to the outside and in both of these cases things are entering from above not sunlight but blood is entering from above and in on the right atrium the blood is entering from above and in the left atrium the blood is entering and remember the left interest on the right hand side from our point of view on the left atrium the blood is entering from above from the lungs from the pulmonary veins veins go to the heart then it goes into and I'll go into more detail into the left ventricle and then the left ventricle pumps that oxygenated blood to the rest of the body to the rest of the body via the non pulmonary artery so everything you saw it pumps out let me make it a nice dark non blue color so it pumps it out through there you don't see it right here the way it's drawn it's a little bit of a strange drawing or it's hard to visualize but I'll show it in more detail and then it goes to the rest of the body and let me show you that detail right now let me show you that detail right now so we said we have deoxygenated blood let's label it right here this is the superior vena cava this is vein this is a vein from the upper part of our body from our arms and heads this is the inferior vena cava this is veins from our abdomen and from our legs and the rest of our body so it first enters the right atrium remember it's the right hand we call it the right atrium because this is someone's heart facing us even though this is on the left hand side it enters through here it's deoxygenated blood it come is coming from veins the body used the oxygen then it shows up in the right ventricle right these are these are valves in our in our heart and it passively once the right ventricle pumps and then releases it has a vacuum and it pulls more blood from the right atrium it pumps again and then it pushes it through here now this blood right here to remember this one still is deoxygenated blood deoxygenated blood it goes to the lungs to become oxygenated so this right here this right here is the pulmonary I'm using the word pulmonary because it's going to or from the lungs or it's dealing with the lungs and it's going away from the heart it's the pulmonary sorry the way is artery pulmonary artery and it is no it's deoxygenated deoxygenated then it goes to the heart rubs on me rubs up against rubs up against some alveoli and then gets oxygenated and then gets oxygenated and then it comes right back now this right here and it comes back just like that this right here we're going to the heart so that's a vein we're dealing where it's it's in the loop with the lungs so it's a pulmonary pulmonary vein and it rubbed up against the alveoli and got the oxygen diffused into it so it is oxygenated oxygenated and then it flows into your left atrium now the left atrium once again from aqua energies on the right hand side but from the dude looking at us it's his left hand side so it goes into the left atrium now on the left ventricle after it's done Bing it expands and so that that blood that oxygen blood flows into the left ventricle then the left ventricle the ventricles are what do all the pumping it squeezes and then it pumps the blood it pumps the blood into the aorta now the aorta this is and this is an artery this is an artery why is it an artery because we're going away from the heart is it a pulmonary artery no we're not dealing with the lungs anymore the lungs we dealt with the lungs when we went from the right ventricle went to the lungs in a loop back to the left atrium now we're in the left ventricle we pump we pump into the aorta now this is to go to the rest of the body this is an artery a non pulmonary artery and it is oxygenated and I want to make this so when we're dealing with non pulmonary arteries were oxygenated but a pulmonary artery has no oxygen it has two going away from the heart to get the oxygen pulmonary vein comes from the lungs to the heart with oxygen but the rest of the veins go to the heart without oxygen because they want to go into that loop on the pulmonary loop right there so I'll leave you there hopefully that gives actually let's let's go back to that first diagram I think you have a sense of how about the heart is dealing but let's go look look at the rest of the body and just get a sense of things I can you know I can you know you can look this up on Wikipedia if you like all of these different branching points have different names to them but you can see right here you can see right here you have a kind of a branching off a little bit below the heart this is actually the celiac trunk celiac trunk celiac if I remember correctly kind of refers to an abdomen so this this blood that you're the blood that need your hepatic artery hepatic deals with the liver you're her patek artery branches off of this to get blood flow to the liver it also gives blood flow to your stomach so it's you know it's very important to ingestion and all that and then let's say this is the hepatic trunk you know your liver is sitting like that hepatic trunk it delivers oxygen the liver the liver is using the is doing respiration it get takes up the oxygen and then and then it gives up carbon dioxide so it becomes D oxygen and then it flows back it flows back in into the inferior vena cava into the vein I want to make it clear it's a loop it's a big loop the blood that there doesn't like just flow out someplace and then come back someplace else this is just one big loop and if you want to know at any given point in time depending on your size there's about five liters five liters of blood and I looked it up on average it takes the average red blood cell to go from that one point in the circulatory system and go through the whole system and come back 20 seconds that's an average because you can imagine there might be some blood red blood cells that get stuck someplace and take a little bit more time and some go through the completely perfect route actually the twenty seconds might be closer to the perfect route I've never timed it myself but it's an interesting thing to look at and to think about what's connected to what that you have these these arteries up here that they have first branch off the arteries up here into from the aorta into the the head and the the neck and the arm arteries and then later they go down and then you they they they flow blood to the rest of to the rest of the body so anyway this is a pretty interesting idea in the next video what I want to do is talk about how does how do how does the hemoglobin know how does it know when to dump the oxygen or even better where to dump the oxygen because you know maybe I'm running so I need a lot of oxygen in the capillaries around my thigh muscles I don't need them necessarily in my hands how does that body optimize where the oxygen is actually delivered it's actually fascinating