1 00:00:01,973 --> 00:00:06,469 If you gave a good long listen to your heart, you might notice that it makes sounds. 2 00:00:06,469 --> 00:00:11,625 Those sounds are usually described as lubdub, lubdub, lubdub. 3 00:00:11,625 --> 00:00:18,971 If you ever tried to figure out what that would spell out like, usually it's something like lubdub. 4 00:00:18,971 --> 00:00:21,074 This repeats over and over and over. 5 00:00:21,074 --> 00:00:26,636 To figure out where those sounds come from, what I did was, I took the diagram of the heart that we'v been using 6 00:00:26,636 --> 00:00:31,748 and exaggerated the valves, made them really clear to see in this picture. 7 00:00:31,748 --> 00:00:36,868 We'll use those valves to talk through where those sounds are coming from. 8 00:00:36,868 --> 00:00:42,616 Let's start by labeling our heart, at the top blood is coming into the right atrium, 9 00:00:42,616 --> 00:00:46,078 going to the right ventricle, it goes of to the lungs, 10 00:00:46,078 --> 00:00:50,046 comes back into the left atrium and then the left ventricle. 11 00:00:50,046 --> 00:00:53,569 These are the chambers of our heart. 12 00:00:53,569 --> 00:00:58,136 Keep your eye on the valves and we'll talk about them as the blood moves through. 13 00:00:58,136 --> 00:01:03,678 Let's start with blood coming from the right atrium, this way into the right ventricle. 14 00:01:03,678 --> 00:01:08,305 At the same moment blood is going from the right atrium to the right ventricle, 15 00:01:08,305 --> 00:01:12,073 blood is actually also going from the left atrium to the left ventricle. 16 00:01:12,073 --> 00:01:16,702 You might think 'How's that possible? How can blood be in two places at one time?' 17 00:01:16,702 --> 00:01:20,673 Remember that blood is constantly moving through the heart, 18 00:01:20,673 --> 00:01:26,201 so from a previous cycle you've got blood that's coming back from the lungs 19 00:01:26,201 --> 00:01:28,536 and that's what's dumping into the left ventricle. 20 00:01:28,536 --> 00:01:33,971 In the new cycle you have a bit of blood that's going from the right atrium to the right ventricle. 21 00:01:33,971 --> 00:01:41,337 You have simultaneously two chambers that are full of blood, the right and left ventricle. 22 00:01:41,337 --> 00:01:45,668 To get the blood into the ventricles, the valves had to open. 23 00:01:45,668 --> 00:01:58,925 Let's label all the valves. Here you have our tricuspid valve. 24 00:01:58,925 --> 00:02:06,679 Up here you have the pulmonary valve. 25 00:02:06,679 --> 00:02:14,923 On the other side you have the mitral valve, which separates the left atrium from the left ventricle. 26 00:02:14,923 --> 00:02:18,872 Here you've got the aortic valve. 27 00:02:18,872 --> 00:02:22,089 These are the four valves of the heart. 28 00:02:22,089 --> 00:02:29,343 As the blood is now in the ventricles, you can see that the tricuspid and the mitral valve are open. 29 00:02:29,343 --> 00:02:35,441 I've drawn the pulmonary valve as being open, but is that really the case? 30 00:02:35,441 --> 00:02:41,770 The answer is no, because what happens is that as blood is moving down from the atrium to the right ventricle, 31 00:02:41,770 --> 00:02:48,105 let's say that, and I'm gonna draw it in black, black arrows represent the wrong direction of flow, 32 00:02:48,105 --> 00:02:54,134 let's say some blood is trying to go that way, which is not the way it should be going, 33 00:02:54,134 --> 00:03:04,666 what happens is, these two valves, based on their shape, they're gonna jam up like this. 34 00:03:04,666 --> 00:03:08,204 They're not gonna let blood pass through. 35 00:03:08,204 --> 00:03:11,270 This is what happens, that valve closes down. 36 00:03:11,270 --> 00:03:19,072 The same thing happens on this side. Imagine you have some blood flowing back by accident. 37 00:03:19,072 --> 00:03:22,501 Then these valves are going to close down. 38 00:03:22,501 --> 00:03:29,168 The white arrows represent the correct flow of the blood and the black arrows the incorrect flow of the blood. 39 00:03:29,168 --> 00:03:31,706 These valves shut down like that. 40 00:03:31,706 --> 00:03:39,973 You can see how the pulmonary and aortic valve are closed when the tricuspid and mitral valve are open. 41 00:03:39,973 --> 00:03:41,669 What happens after this? 42 00:03:41,669 --> 00:03:46,570 The ventricles are full of blood and let's say they squeeze. 43 00:03:46,570 --> 00:03:55,936 They squeeze down and they jam all the blood into the arteries. 44 00:03:55,936 --> 00:04:03,635 This is going to close down. This arrow flips around. 45 00:04:03,635 --> 00:04:09,973 These arrows become white because the flow is gonna be in the direction we want it. 46 00:04:09,973 --> 00:04:11,585 It's gonna go this way and this way. 47 00:04:11,585 --> 00:04:18,207 And to allow that, I'll have to show you, these open up. 48 00:04:18,207 --> 00:04:22,418 They allow the blood to go the way we want it to go. 49 00:04:22,418 --> 00:04:26,507 Now, blood is gonna flow through those two valves. 50 00:04:26,507 --> 00:04:31,588 Similar to before, you could have some back flow here, right? 51 00:04:31,588 --> 00:04:35,042 You can have back flow here and you can have back flow here. 52 00:04:35,042 --> 00:04:41,736 You can imagine, let's say you have a little back flow that wants to go this way, which is the wrong direction, 53 00:04:41,736 --> 00:04:45,088 then these valves are gonna close up. 54 00:04:45,088 --> 00:04:49,433 They'll say 'No, you can't go that way.' They're gonna close up. 55 00:04:49,433 --> 00:04:54,248 They won't allow blood to go that way. 56 00:04:54,248 --> 00:05:00,374 This happens on both sides and the valves shut. 57 00:05:00,374 --> 00:05:06,406 The back flow of blood is not allowed because the valves keep shutting. 58 00:05:06,406 --> 00:05:15,019 When the valves snap shut, for example the tricuspid and the mitral valve snap shut, 59 00:05:15,019 --> 00:05:16,795 well, that makes a noise. 60 00:05:16,795 --> 00:05:25,576 When T and M snap shut, that will make a noise that we call lub. 61 00:05:25,576 --> 00:05:29,134 That's that first noise, that first heart sound. 62 00:05:29,134 --> 00:05:38,239 In fact sometimes people don't even call it lubdub, they say, well, it's the first heart sound. 63 00:05:38,239 --> 00:05:42,999 To make that even shorter, sometimes people call that S1. 64 00:05:42,999 --> 00:05:46,586 If you hear S1, you know they're talking about that same exact thing. 65 00:05:46,586 --> 00:05:52,499 This dub is called the second heart sound. 66 00:05:52,499 --> 00:05:57,660 No surprise, just as before, if that's S1, this is S2. 67 00:05:57,660 --> 00:06:06,495 You'll hear S1 when the tricuspid and the mitral valve shut. So far so good. 68 00:06:06,495 --> 00:06:08,832 But you also know that if that is what's making the noise, 69 00:06:08,832 --> 00:06:21,573 you can guess that at the same time the pulmonic and the aortic valve just opened. 70 00:06:21,573 --> 00:06:25,469 If the other valves snap shut, these just opened. 71 00:06:25,469 --> 00:06:31,575 You can kind of assume that, although the noise you're hearing is actually from here. 72 00:06:31,575 --> 00:06:34,635 What's happening with dub? Well, the opposite. 73 00:06:34,635 --> 00:06:39,302 What I mean by that is, let me show you what happens a moment later. 74 00:06:39,302 --> 00:06:50,333 After the ventricles are done squeezing, then we come to a moment when you might have a little bit of flow that way and that way. 75 00:06:50,333 --> 00:06:56,199 Just as I drew before and these valves snap shut as well. 76 00:06:56,199 --> 00:06:58,330 So now these snap shut. 77 00:06:58,330 --> 00:07:08,297 As these snap shut because they don't want to allow back flow, they make noise. 78 00:07:08,297 --> 00:07:20,744 So when you hear dub, you have noise coming from the pulmonic and the aortic valve snapping shut. 79 00:07:20,744 --> 00:07:24,196 That must mean that the other two valves just opened up. 80 00:07:24,196 --> 00:07:27,864 The tricuspid and mitral valve just opened. You can assume that, right? 81 00:07:27,864 --> 00:07:34,265 I didn't draw that in the picture, let me update my picture now to show that. 82 00:07:34,265 --> 00:07:43,640 These two have opened up and blood is coming into the ventricles. 83 00:07:43,640 --> 00:07:49,740 It's actually a nice little rhythm that you get going. 84 00:07:49,740 --> 00:07:56,002 Every time these valves go open and shut, you hear noise. 85 00:07:56,002 --> 00:08:07,655 You can figure out what's happening. 86 00:08:07,655 --> 00:08:10,601 We've returned to where we've started from. 87 00:08:10,601 --> 00:08:17,531 You basically have a full cycle and between these two, let's say from lub to dub, 88 00:08:17,531 --> 00:08:21,470 there's a little bit of space there, if you were to follow it over time. 89 00:08:21,470 --> 00:08:27,200 Over time this is what it might look like if this is a little timeline. 90 00:08:27,200 --> 00:08:36,643 You might hear lub here, our first heart sound, let's call it S1 here, S2 here, the second heart sound. 91 00:08:36,643 --> 00:08:41,536 You'll hear S1 again here and S2. 92 00:08:41,536 --> 00:08:51,105 What's happening between the two, this timeline here, is that blood is actually squeezing out 93 00:08:51,105 --> 00:08:57,415 because the aortic and pulmonic valves just opened, blood is squeezing out and going to the whole body. 94 00:08:57,415 --> 00:09:05,767 This is when blood is going to the body. Or as we call it 'Systole'. 95 00:09:05,767 --> 00:09:20,401 Between dub and the next lub, so in this area, at that point blood is refilling from the atria to the ventricles 96 00:09:20,401 --> 00:09:24,123 and we call that diastole. 97 00:09:24,123 --> 00:09:31,360 Now you can listen to your heart and figure out, well if you listen to the sound between lub and dub, 98 00:09:31,360 --> 00:09:36,317 the space in time between lub and dub, that's when you're having systole. 99 00:09:36,317 --> 00:09:40,317 When you're waiting for the sound to start up again, that space in time is diastole.