By the end of this video, you're going to understand exactly what causes the heart sounds, but also how the sounds can be different when there's a problem. Now, to understand the sounds, we first have to talk about two concepts, the cardiac cycle and blood flow. Let's start with the cardiac cycle. The cardiac cycle includes everything that happens from the beginning of one heartbeat to the beginning of the next. And generally speaking, we can divide it into two phases, systole, and diastole. systole means contraction, and diastole means relaxation. Now, technically, there are more than just those two phases. And you can find out more about those details in my series on the cardiac cycle. And I'll even link to my free cardiac cycle guide in the description below. But for the purpose of understanding the heart sounds, we're just going to look at these two main phases. Now let's briefly touch on blood flow. When blood comes back to the heart from the body, it enters into the atria and then goes to the ventricles, the ventricles then pump that blood back out. On the right side, blood is going to the lungs, and on the left side is going to the rest of the body. Now let's bring those two concepts together at the beginning of systole, the ventricles start to contract, when the ventricles are contracting, one of the first things that's going to happen is the valves between the atria and the ventricles, they shut Now this makes sense because of the blood just came from the atria. And we don't want it to go back there. Instead, we want it to go to the lungs to get the oxygen and also to the body to deliver that oxygen. Those valves are called atrial ventricular valves because they are between the atria and the ventricles make sense, but they also have specific names. On the right side, we call it the tricuspid valve, and on the left side, we call it the mitral valve. And when those valves shut, it's not a silent event, it actually makes a sound. And that's the first sound that we hear when we listen to the heart is the lub of the lub dub sound. It's also called S1, the first heart sound. Now let's move to the second heart sound by going back to the ventricles contracting, they contracted and they pump the blood out on the right side, the blood is going to the pulmonary artery to get to the lungs. And on the left side, the blood is going into the aorta to get to the rest of the body after that contraction. After systole, we get diastole the heart and specifically the ventricles are relaxed. And right at the beginning of that relaxation, the aortic valve and the pulmonary valve, they close by the way, in some places, you might see the pulmonary valve called the pulmonic valve, it's the same thing. And once again, when those valves close, we get another sound. That's the dub of the lub dub, also called S2 the second heart sound. Let's listen to a normal heart sound. See, we have the lub dub, lub dub lub dub 1212. Now it's pretty normal, you can hear it's like a clean sound for the S1. And as to the dub the look. I feel like you can make a beat to this. Okay, so we have the first heart sound S1 and the second heart sound S2. And this is what we hear in a normal heartbeat. But those aren't the only sounds we can hear. There's also an s three and s four. Let's look at S3. S3 is a third sound that is typically heard in children and young adults it happens right after the second heart sound. Now remember, S2 happens right at the beginning of diastole. Right at the beginning of that relaxation phase. Well, during that relaxation phase, blood starts to rush into the ventricle because we are preparing for the next contraction and as the blood rushes into the ventricle, it can cause a third sound S3. Let's listen to that one. See, you hear that third one is a little softer than the second sound. You'll sometimes hear people use the word Kentucky to give an idea of the timing of that third sound Kentucky, Kentucky, Kentucky it's also known as the ventricular gallop because it's the result of blood rushing into the ventricle. And once again, that third sound is common in children and young adults. It's not typically heard in adults, and can be a sign of potential problems with the heart. Okay, now let's look at es four. This one is also known as the atrial gallop. It happens late in diastole. Just before systole that means that it's going to be heard right before a swan. This happens when the atria pump the blood into the ventricles. That's right before the ventricles contract. In some cases, you can hear this when the ventricles are pretty stiff so the blood rushes in and it's bouncing against the stiffer wall and that causes the fourth sound and again, this is right before us one. Let's listen to that one. See, normally you just have that lub dub, lub dub lub dub but now you have something right before or the lob, you'll sometimes see people use the word Tennessee to show that timing Tennessee, Tennessee, Tennessee, Tennessee, Tennessee, Tennessee. So we have that blood being pushed into the ventricle that stiffer than normal, and that's why we get that extra sound. This is usually a sign of some cardiac problems and would need to be evaluated further. Now the last thing I want to touch on is heart murmurs. These are abnormal heart sounds that can occur between the normal s one and S two sounds, and can be a sign of a serious problem, or it can be completely harmless. It's usually an indication of a problem with the valves. Either the valve is leaky or narrower than normal, which results in turbulent blood flow or blood flowing back through the valve. You can imagine if the valve is enclosing fully, some blood can actually sneak through where you don't want it to go. There are generally two types of murmurs, systolic murmurs and diastolic murmur. Systolic murmurs are the most common type, and they happen during systole. That's when the heart is contracting. diastolic murmurs are not as common and they happen during diastole. When the heart is relaxing, let's listen to systolic murmur. See that instead of that clean as one sound, you get kind of a swishing sound with S1, swish schwa. I'm not really good at making these sounds with my mouth, but you get the point. Now let's listen to what diastolic murmur in this case, you get kind of a swishing sound with S2 by the way swishing isn't like a technical term. It's just what it sounds like to me. Now let's see an even worst case where there's both a systolic and diastolic murmur. And that junk sounds like blood is just squirting all over the place. Not good. But as you can tell by just listening, it appears that some blood is getting through where it shouldn't be getting through and the S1 and S2 are not as clean as you would want it to be. Shear ventures going everywhere. Crazy no In all these situations, just hearing one of these sounds isn't necessarily a sign of a problem. Any abnormal heart sound should be carefully evaluated by a healthcare professional to determine its significance and if treatment is necessary to fully understand these heart sounds and how it all fits into heart function. I highly recommend for you to check out my video on the cardiac cycle because that will give you a better foundation in understanding exactly how the heart works.