0:00:02.132,0:00:04.826 I really like this picture that I found. It actually 0:00:04.826,0:00:08.465 shows you really neatly where the heart sits in our body 0:00:08.465,0:00:12.543 so you can see the heart is surrounded, on both sides, by ribs, right? 0:00:12.543,0:00:16.200 And in fact, I didn't draw it in yet, but let me show you where the 0:00:16.200,0:00:20.080 lungs would be. This is the right lung 0:00:20.080,0:00:23.464 and on this side you'd have the left lung. So this is where 0:00:23.464,0:00:27.543 your heart sits: between two lungs. And I'm saying 0:00:27.543,0:00:31.424 left and right from the perspective of the the person who owns this 0:00:31.424,0:00:35.700 heart. So this is their left and right, which is the opposite 0:00:35.700,0:00:39.328 of us if we're looking at it. The heart is actually sitting between the two 0:00:39.328,0:00:42.952 lungs within this protective casing that 0:00:42.952,0:00:47.072 the ribs are basically there to keep all these important organs 0:00:47.072,0:00:51.108 safe. And then below them, so if you draw 0:00:51.108,0:00:55.529 this here. Or if I draw it, you can 0:00:55.529,0:00:58.606 see now that below all this stuff is 0:00:58.606,0:01:02.865 a really really important muscle. So this muscle 0:01:02.865,0:01:07.309 people don't talk about this muscle, or this is not the kind of muscle 0:01:07.309,0:01:10.847 that you usually see people working on at the gym, but this muscle is called the diaphragm. 0:01:10.847,0:01:15.113 So your diaphragm muscle 0:01:15.113,0:01:22.841 and your ribs are enclosing a space, right? The diaphragm becomes the floor, and the ribs are kind of the 0:01:22.841,0:01:25.686 ceiling and the walls of this space. 0:01:25.686,0:01:30.188 And if you look at the contents of this space, you'd have your lung 0:01:30.188,0:01:33.770 and you'd have your heart. So, this entire space then 0:01:33.770,0:01:38.856 is called your thorax. 0:01:38.856,0:01:42.267 So what exactly does the heart do? Let's actually make a little bit of 0:01:42.267,0:01:45.836 space now, and bring up a 0:01:45.836,0:01:47.770 zoomed in version of the heart. 0:01:47.770,0:01:53.969 Let me start by orienting you to the heart. This is our right lung 0:01:53.969,0:01:58.035 and on the other side we have our left lung. And all this would be 0:01:58.035,0:02:01.375 inside of the rib cage, but I'm not going to draw that now, because that would 0:02:01.375,0:02:05.498 make it harder to see the heart itself. So to think 0:02:05.498,0:02:09.732 about exactly what the heart does, I think one, kind of neat way to do it is 0:02:09.732,0:02:13.434 to actually imagine that you're a cell. So put yourself in the perspective 0:02:13.434,0:02:17.361 of a cell, and let's say you're a cell hanging out 0:02:17.361,0:02:21.195 over here. This is you. And you can 0:02:21.195,0:02:25.013 think about any part of the body that you could be. Let's say a little 0:02:25.013,0:02:27.977 toe cell. So let's say you're a toe cell 0:02:27.977,0:02:32.737 and your job, of course, is to live and be happy,and you've got 0:02:32.737,0:02:36.834 near by, a little blood vessel. And in fact, every cell in our body 0:02:36.834,0:02:40.791 has a little blood vessel that's near by. And this toe cell 0:02:40.791,0:02:44.209 is just trying to make a living. And toe 0:02:44.209,0:02:48.914 cells need certain things, right? They need, for example, let's say oxygen. 0:02:48.914,0:02:52.815 I'll write it in white so it's very clear. They need oxygen 0:02:52.815,0:02:56.589 and they need nutrients, right? 0:02:56.589,0:03:00.429 So cells need certain things to live and be happy. 0:03:00.429,0:03:03.938 And on the flip-side, they also make waste. They're in 0:03:03.938,0:03:08.269 a sense just like us, they make waste. And that waste could be 0:03:08.269,0:03:12.525 all sorts of things, and one that kind of jumps to mind is 0:03:12.525,0:03:15.197 carbon dioxide (CO2). So carbon dioxide is waste 0:03:15.197,0:03:19.394 for this cell. So it's making some 0:03:19.394,0:03:23.494 waste and for the moment let's imagine that there's no blood flow. 0:03:23.494,0:03:26.044 So, even though there's a blood vessel near by, 0:03:26.044,0:03:29.905 really, no flow is happening, so I'll just write "no flow". 0:03:29.905,0:03:34.306 So as the little cell 0:03:34.306,0:03:38.949 makes waste. That waste, let's draw a little ball right here, 0:03:38.949,0:03:42.078 it's going to start accumulating, you're going to start collecting more and more of it 0:03:42.078,0:03:45.462 since the blood is not really flowing. And it might kind of 0:03:45.462,0:03:50.435 end up getting all the way around our toe cell. So our toe cell is getting 0:03:50.435,0:03:54.100 swamped, literally getting kind of covered by its own waste. 0:03:54.100,0:03:58.759 And on the flip-side, is it getting oxygen or nutrients? No. 0:03:58.759,0:04:01.945 It's not getting either of these things. So, before very 0:04:01.945,0:04:06.133 long, I would say within minutes, our toe cell 0:04:06.133,0:04:09.637 is thinking, "Well this is not a very happy way to live!" this is 0:04:09.637,0:04:13.245 actually really very sad, this is awful. And if this continues 0:04:13.245,0:04:17.418 the toe cell would die. So, what a toe 0:04:17.418,0:04:20.630 cell needs, and what every cell needs, and that could be a finger cell or a 0:04:20.630,0:04:25.199 skin cell, or really any cell that's living, needs 0:04:25.199,0:04:29.349 flow. Right? It needs this blood to be flowing nicely 0:04:29.349,0:04:31.623 and smoothly. And if there is flow 0:04:31.623,0:04:36.244 then you get a very different picture, right? If there's flow then all the sudden all the 0:04:36.244,0:04:39.564 waste product is actually now lifted and taken away. 0:04:39.564,0:04:43.182 It's flowing away, and it's a little bit like having 0:04:43.182,0:04:48.294 someone come by and pick up the trash, then you don't have trash all over the house. 0:04:48.294,0:04:51.289 So then you have nice flow, and 0:04:51.289,0:04:56.135 in return, oxygen and nutrients are delivered. So this stuff 0:04:56.135,0:04:59.613 gets delivered as well. So, all of the sudden the cell is going to be 0:04:59.613,0:05:03.606 very, very happy, and is going to be living just fine. 0:05:03.606,0:05:06.977 So, really if you want all of the cells in your body to be living just fine 0:05:06.977,0:05:11.414 like this cell here, you really want good flow throughout the 0:05:11.414,0:05:15.100 body. And so this is really point number one. Is that you really 0:05:15.100,0:05:19.068 need, somehow, to have blood flow moving and pushing 0:05:19.068,0:05:22.117 blood constantly through the body. So, 0:05:22.117,0:05:27.741 to do this for billions and billions of cells you would need a pretty powerful 0:05:27.741,0:05:31.034 pump, right? Something that's going to be able to pull 0:05:31.034,0:05:35.281 in all the blood from the body, and then push it back out. And that's what the heart 0:05:35.281,0:05:39.223 is. I mean at its core, that's exactly what the heart is doing. 0:05:39.223,0:05:42.910 It's an amazing pump, pushing blood, so that 0:05:42.910,0:05:45.540 you have good blood flow. And so I'm 0:05:45.540,0:05:49.524 going to write that on the side as kind of job number one. These are the jobs of the heart. 0:05:49.524,0:05:53.479 So jobs, and number one, would be 0:05:53.479,0:05:56.045 blood flow. And I'll write systemic 0:05:56.045,0:06:01.049 flow. Systemic flow. And all 0:06:01.049,0:06:05.043 that systemic means is that I'm refering to the entire body. So systemic 0:06:05.043,0:06:08.782 when I say that word, I just mean the entire body. All the cells 0:06:08.782,0:06:12.861 in the body. Now, exactly how that happens actually 0:06:12.861,0:06:16.508 you can see on this picture. So, here you have a giant 0:06:16.508,0:06:20.656 vein, this is a vein, and you have an artery. 0:06:20.656,0:06:23.602 This is an artery. 0:06:23.602,0:06:28.698 And blood is actually going through the artery, that way. 0:06:28.698,0:06:32.938 And it's actually coming into two veins, the one 0:06:32.938,0:06:36.820 at the top, this is called the superior, superior just kind of means 0:06:36.820,0:06:40.490 at the top. Superior vena cava. That's the 0:06:40.490,0:06:44.382 name of the vein. And at the bottom here, you can't see it because 0:06:44.382,0:06:48.496 it's on the other side of the heart, but there's another vein called the inferior vena cava. 0:06:48.496,0:06:51.522 And these two veins, this is also a vein, 0:06:51.522,0:06:57.533 these two veins are actually dragging blood in from all over the body, 0:06:57.533,0:06:59.406 into the heart. 0:06:59.406,0:07:02.906 And then, when the heart is ready to pump it back out, it goes into this 0:07:02.906,0:07:07.256 artery, and the name of it is the aorta. 0:07:07.256,0:07:10.827 So if you've heard of the aorta, this is the artery that people 0:07:10.827,0:07:14.856 are talking about. So this is how blood comes and gets pumped 0:07:14.856,0:07:18.775 around. But this isn't actually the only job of the heart. The job, 0:07:18.775,0:07:22.465 the second job of the heart, is actually 0:07:22.465,0:07:26.536 also in this picture, and it's called pulmonary flow. 0:07:26.536,0:07:30.517 Pulmonary flow. So, what does that 0:07:30.517,0:07:34.116 mean? Well, we know that cells are expecting 0:07:34.116,0:07:39.079 oxygen, right? We know this. And that they have a lot of carbon dioxide 0:07:39.079,0:07:42.322 waste. Well, it's good to move things around. It's good 0:07:42.322,0:07:45.399 to move blood around. But if you actually never got rid of that carbon dioxide 0:07:45.399,0:07:49.786 or brought in new oxygen, then a cell is not going to be very happy either. 0:07:49.786,0:07:53.107 I mean, you can have blood flow, but at some point it's also going to want some oxygen. 0:07:53.107,0:07:57.271 And it's going to want to get rid of that carbon dioxide. So, that's where the 0:07:57.271,0:08:00.911 lungs come in. So what happens is that the heart, before 0:08:00.911,0:08:05.436 sending blood out the aorta, before just dishing it out back into the body, 0:08:05.436,0:08:09.411 it actually sends the blood over to the 0:08:09.411,0:08:12.895 lungs. And it goes over to the left lung, and over to the right lung. 0:08:12.895,0:08:17.186 And the blood comes back from the right lung 0:08:17.186,0:08:21.280 and the left lung, and gets pushed back into 0:08:21.280,0:08:24.629 the heart, and then gets squeezed through the aorta. So there's this 0:08:24.629,0:08:28.223 actual extra little step here, where blood is going to 0:08:28.223,0:08:32.528 and from the lungs, and that's the pulmonary flow. 0:08:32.528,0:08:36.813 So the final thing you'll notice, if you look at this picture it's hard not to notice, 0:08:36.813,0:08:40.196 is that there are these, kind of wriggly looking little 0:08:40.196,0:08:44.344 blood vessels all over the heart. And what are these 0:08:44.344,0:08:47.030 exactly? I mean, you've got red ones, and blue ones, and 0:08:47.030,0:08:50.356 the blue ones are the veins, and the red ones are the arteries 0:08:50.356,0:08:55.270 but are they part of the systemic flow, or pulmonary flow, or something else? 0:08:55.270,0:08:58.476 Well, these vessels, all of them, 0:08:58.476,0:09:01.943 together are called coronary vessels. 0:09:01.943,0:09:06.929 And so specifically you might hear about 0:09:06.929,0:09:10.720 a coronary artery, or a coronary vein, but together you can call them 0:09:10.720,0:09:14.450 coronary blood vessels. I'll add the word blood here. So these 0:09:14.450,0:09:18.109 coronary blood vessels are actually serving the heart muscle 0:09:18.109,0:09:20.715 itself. I mean remember, the heart 0:09:20.715,0:09:24.724 is made up of thousands and thousands, actually tens of thousands of cells 0:09:24.724,0:09:29.948 and those cells, just like our toe cell that we drew, 0:09:29.948,0:09:33.636 they also need oxygen, nutrients, and have waste. 0:09:33.636,0:09:37.223 So, those cells are going to need blood vessels supplying 0:09:37.223,0:09:40.319 them as well. So, that's what the coronary blood vessels are. They're literally 0:09:40.319,0:09:43.835 the blood vessels that go to and serve 0:09:43.835,0:09:47.735 the heart. So these are the ones that serve the heart. 0:09:47.735,0:09:51.059 Now, if they're serving the heart muscles 0:09:51.059,0:09:55.616 and the heart cells, then, think about it, would they fit under 0:09:55.616,0:09:59.304 the systemic flow, or pulmonary flow? Well if the 0:09:59.304,0:10:03.411 main job is to serve the needs of cells, then 0:10:03.411,0:10:08.167 the coronary vessels fall under the systemic flow.