Hello, everyone. In this lesson, we are going to be talking about blood pressure, and how blood pressure changes depending on the different veins, arteries, and capillaries the blood is actually in. Okay. So first off, let's talk about the 2 different types of blood pressure. So I'm sure you've had your blood pressure taken by your doctor, and your doctor gives you these numbers. Generally, they're around 120 over 80. And that actually is your blood pressure, but it's actually 2 different versions of blood pressure. The systolic blood pressure is the top part of the fraction, and the diastolic blood pressure is the bottom part of the fraction. So what's the difference between these 2? Because if you are a pre-med student, you're definitely going to have to know these 2 different types of blood pressure.
The first one, the highest number is gonna be your systolic blood pressure. And this is the highest blood pressure that your arteries should actually experience, and that your heart should actually experience. And systolic blood pressure is going to be taken at the time in the heart phases called systole. And systole is going to be the peak of contractions. So this is the peak of blood pumping out of the ventricles. So whenever the ventricles actively contract and push that blood out of the ventricles, that blood's gonna be of extremely high pressure because those muscles are actively squeezing on it. So Systolic Blood Pressure is the highest blood pressure because this is gonna be the pressure of the blood when the ventricles are actively contracting during the phase called Systole. Systole is going to have a range of healthy blood pressures. During the contraction phase, or systolic phase, the healthy blood pressure should be less than 120 millimeters of Mercury, which is going to be a measurement of pressure. So anything less than 120 millimeters of mercury is good. So around that range is a good systolic blood pressure. Anything above 140 is going to be problematic and is going to cause high blood pressure, which is not good for your body.
Now, the second form of blood pressure is the diastolic blood pressure. This is gonna be the one on the bottom of the fraction when you're given your blood pressure. And this is the lower blood pressure that you experience, and it's the lower blood pressure because it's actually right before the ventricles contract and pump out blood. And this is because this is gonna be the blood pressure of the Diastole Phase in the Heart Contraction Phase. And this is actually the relaxation phase, and this is actually when the chambers of the heart are refilling with blood right before the contraction phase, right before systole. So, this is going to be the very low blood pressure of the heart and of the blood because this is when the heart is relaxing and when the heart is actually refilling with blood, so it can do another cycle of contractions. And this blood pressure also has an optimal blood pressure, and this is anything under 80 millimeters of Mercury. Anything above that is considered high blood pressure and can be dangerous. So that's why they say that you want your blood pressure to be around 120 over 80. So, let me draw this out for you guys. So your fraction would look like this: 120 over 80 millimeters of Mercury. And this one right here is the Systolic. And this one right here is the Diastolic. So that's why you get two numbers whenever you get your blood pressure reading. Okay?
Alright. So now, we use blood pressure to understand how the heart is functioning. So whenever your heart is beating, your arteries actually will bulge because the pressure and the force of the blood is increasing. So you guys can generally put your hands up next to your neck and find an artery, and then it will be pulsing. And that is because with every beat and contraction of your heart, more blood is being pushed through that artery, so it is going to expand. Okay? So the pulse is gonna tell you about the heartbeat, how quickly those contractions are happening, and the blood pressure is going to tell you the pressure of the blood and how much force is being put on that blood. Okay?
So now let's talk about high blood pressure because Americans do have an issue with this, and this is also called hypertension. And hypertension is long-term high blood pressure. This is anything over 120, especially over 140 systolic blood pressure. Anything over that for a very long period of time is called hypertension. Hypertension is generally seen in Americans because we have a very high salt diet, but hypertension can be caused by a high salt diet, a high fat diet, and a lack of exercise. And hypertension can lead to a lot of issues. You can imagine if you have a lot of pressure on your heart and on your arteries and your veins all the time throughout your entire life, you're going to have some issues from that. And this can cause Coronary Artery Disease. This can cause a stroke. This can cause kidney disease. It can cause a whole bunch of issues. So hypertension is generally bad, and this is generally medicated for, or the diet is changed. But I want you guys to know that this is generally caused by diet, but it can also be caused by genetics as well. Some people have a higher propensity to have hypertension than others. Okay?
Alright. So now let's look at this really neat graph, which is gonna be showing us the pressures of these different areas of your cardiovascular system. So what we have is we have the pressures of these different vessels. So you have the aortic pressure, which is gonna be the pressure of your aorta, which is the largest vessel in your body. And the left ventricle is going to push blood into the aorta. And we're going to have the pressure inside of the atria's, and we're gonna have the pressure inside of the ventricles. Now, just so you guys know, whenever you're measuring blood pressure, you're generally measuring the pressure of the aorta, the major arteries of the body. So whenever you're looking at these pressures on this chart, the one we generally go by to measure pressure of the blood is this one in red right here. The Aortic Pressure is generally what we utilize. And if you guys can see, the way we know that is true is because we have the 120 and we have the 80. That's the general healthy blood pressure for an individual, and that's how you know this is the one that we're measuring. We're measuring the aortic Pressure. Okay?
Alright. So, you guys know that we're measuring the Aortic Pressure, and I would like to show you the different phases of the heart's contraction. So, the phase that is happening right here is Systole. This is the contraction phase. All of this right here is the 120. That's gonna be the highest pressure when those ventricles are actively contracting and pushing the blood out. And then once systole is ending, well, the heart is actively refilling with blood. So the pressure here is much lower. And you guys can see that the atria and the ventricles also do change in pressure. You can see the ventricle pressure in black changes substantially. You guys can see that it's way down here, and then during systole, it just jumps up to these huge pressures, and that's because the blood inside of the ventricle is being actively squeezed and being given a ton of pressure, and it's just shooting that blood out of the ventricles, and then it's gonna dramatically drop back down during diastole, and the drop in blood pressure actually aids the heart in pulling more blood into it. So this is basically showing you the different pressures that the different areas of the heart and the different vessels experience. So the aorta is in red, and that is what we generally utilize for blood pressure. That's what we use to read blood pressure is the aortic pressure. But then we also have the ventricular pressure in black, and we have the atrial pressure in blue. And they're all going to vary, but the one that's most dramatic is the ventricular pressure because it greatly jumps up during systole. Okay, guys?
Alright. So now let's go down and let's talk about how the blood vessels are going to deal with this gigantic change in pressure. Because the arteries are the vessels leading away from the heart, and they're going to experience the most intense blood pressure, especially the aorta, which is going to experience the most intense blood pressure because that left ventricle is actively pushing blood into it. So the way they're going to combat this is that arteries have muscle fibers, and elastic fibers help them deal with the high pressure. So this is going to be these muscle fibers and these fibers that help it stretch and help it go back to its normal size during the different contractions of the heart. And the aorta is especially dense with these elastic fibers because it goes through this immense systolic blood pressure, this immense change in pressure every time those ventricles contract. Those fibers are there to help that, to help make sure that these arteries don't burst. They need to be able to withstand this giant change in pressure. So now the arteries are going to have the highest blood pressure. The arteries are the vessels leading away from the heart, and the arteries are the vessels that are actively being pushed blood into. So they have the highest blood pressure. The veins and the capillaries are gonna have the lowest blood pressure. Remember, the capillaries are where n