Placeholder Image

字幕列表 影片播放

  • Hi. It's Mr. Andersen and I was just checking my pulse to make sure that

  • I'm still alive. And I am. I'm going at about 60 beats per minute and it will continue doing

  • that throughout the podcast and hopefully throughout the rest of my life. Because the

  • circulatory system is important, it moves oxygen around my body. It moves carbon dioxide

  • out of my body. It moves nutrients to the cells in my body. And so we need it to keep

  • beating. And it does. Something that we kind of take for granted. Before we get to the

  • elements of the human circulatory system you should know that there are different types

  • of circulatory systems. In things like insects and spiders they don't have blood per se.

  • They have something called hemolymph. And that hemolymph is going to be both blood and

  • what's called interstitial fluid. Interstitial fluid is going to be the fluid that bathes

  • the cells inside us. In an insect those things are combined together and that's why if you

  • squash a bug you get that goo that comes out of the bug. But in us we put our blood inside

  • blood vessels and then the interstitial fluid is going to be everywhere else inside our

  • body. And so we keep those separate. And so that's the difference between a closed and

  • an open circulatory system. In animals we also have a variety of different hearts. And

  • so a fish, something like this that lives in water, it simply has a two chambered heart.

  • And so it's heart has 1, 2 chambers. It's separated by a valve and the reason why is

  • that they live in water. And so when you're looking at the pictures of hearts on the next

  • few slides, I don't want you to look at the heart as much as I want you to look at the

  • loops that come from that. And let me make it a little simpler. I'm going to get rid

  • of half of this diagram. Because half of it is just the left side of the fish. Okay, so

  • if we look at it what do we have? We have one single loop. So the blood is going to

  • go to the gills where it's going to get oxygen and then it's going to go to the body and

  • then it's going to continue back to the heart. So we only have one loop. And that works great

  • in water. But when you move onto land you lose quite a bit of that pressure as you go

  • to the gills, or if on land as you go to the lungs, and so it simply isn't a system that

  • works. And so that's why on land we have a three chambered heart. So things like this

  • bearded dragon over here have a three chambered heart. What does that mean? Well let me again

  • draw it right down the middle and get rid of half of the diagram. This makes it easier.

  • What we now have is we have two loops. And so we have one loop that goes to the lungs

  • and then it comes back to the heart. And then we have another loop that goes to the rest

  • of the body. And so that deals with that pressure issue. But one thing that's interesting is

  • that instead of just having red and blue blood we now have this purple blood. What does that

  • mean? We're getting a mixing of the blood. In other words we're having a mixing of the

  • oxygenated blood in the red and the deoxygenated blood in the blue. An that's because we only

  • have 1, 2 because these ones are combined, 3 chambers in the heart. And so once we become

  • endothermic, one we become warm-blooded and need quite a bit of energy, that's not efficient.

  • And so in birds and mammals we have a four chambered heart. And so basically what we've

  • done is we've sealed up that third chamber. Now we have one, two, three, four chambers

  • to the heart. We still have a double loop. And so that's more efficient. And those have

  • evolved as we've had different constraints depending on the environment and where they

  • live. So what does blood do? Blood follows a loop. And so it's going to start at the

  • heart. It's going to move throughout rest of the body in arteries, arterioles eventually

  • down to capillaries and then come back again. And so it keeps moving around your body. It's

  • moving nutrients and it's moving that carbon dioxide out and it's moving oxygen to the

  • parts of your body that need it. Let's start with the heart then because it's important

  • that you understand the chambers of the heart and where blood is essentially going. Whenever

  • you see a diagram like this you want to kind of imagine yourself shifted into the heart.

  • So imagine yourself in this heart right now kind of turn yourself, in your brain, inside

  • it. So basically your right side now is going to be over here and your left side is going

  • to be over here. And so that's pretty important. So let's start with deoxygenated blood. Deoxygenated

  • blood means that it's coming back from your body. So where does it come from? It's coming

  • from your superior and inferior vena cava. So basically it's entering into what's called

  • your right atrium. So this would be your right atrium here. So we've got deoxygenated blood

  • coming back, it's in your right atrium. It then goes through this valve here. This valve

  • is called the AV valve. Sometimes we call it the tricuspid valve, but the blood is now

  • going to go from here into the ventricles. So it's going to go into your right ventricle.

  • It's then going to move out through this semilunar valve, semilunar valve, it's going to move

  • into what's called the pulmonary artery. So this would be the pulmonary artery here. What's

  • interesting about the pulmonary artery is it's an artery that has deoxygenated blood.

  • And the reason why is it's headed to the lungs. So the blood is going out that artery. That's

  • what an artery is. It moves away from the heart into the lungs and now it becomes oxygenated.

  • So that oxygenated blood is going to come back into here, that's going to be your left

  • atrium. And I can't write on that because you won't see it. So it's going to go into

  • your left atrium which is right there. It's then going to flow through our left AV valve

  • down into this ventricle. So this would be our left ventricle inside there. And then

  • it's going to be move out the back into this big artery. And that's called the aorta. So

  • it goes through the aorta. So there's an aorta down here and then this aorta as it move up

  • here is going to send up arteries that go up to the head. It's then going to go to the

  • body and then it's going to come back again. And so I should be able to clear all of those

  • out and you should pause the video right now and can you do that? Can you go form the superior

  • and inferior vena cava all the way to the aorta? And if you can, awesome. If not, you

  • may want to kind of go back and look at that again. Okay, so what are the blood vessels?

  • Because those are kind of what we don't see when we moved off the screen there. Well basically

  • they go from the arteries to the arterioles. So here's an artery right here. It's then

  • going to go to the arterioles and then it's going to go to the capillaries and then it's

  • going to go back to the venules and then it's going to go back to the veins. And so most

  • of the pressure is being handled by the arteries and the veins. And so the red is going to

  • be the arteries moving away from the heart and the blue is going to be the veins coming

  • back. One quick side note, blood is red. It's always red And some kids get confused because

  • they see diagrams like this and they think blood is blue and somehow if you somehow cut

  • yourself it turns from blue to red. That's just a silly story. It's just not true. So

  • I hope I didn't shatter too many dreams that you had. It's always red. And some people

  • say "Well look at my veins, they're blue." And I would say "'You're right, that's the

  • connective tissue in those veins but it's not the blood. The blood is red." Sometimes

  • it's really red, but it's red, it's red, it's red. Okay. So how do the arteries differ from

  • the veins? The arteries differ from the veins in a few ways. Number 1, they're not going

  • to be as strong, there's not as much connective tissue around it. But they also have valves

  • in them. Because once that blood has gone all the way down to the bottom, down here

  • to your feet, it has to get it's way all the way back to your heart. We've lost a lot of

  • that pressure. And so as the blood flows up, we have veins, we have valves that are found

  • in the veins and so it will actually move up. And then it can't go back down again because

  • this closes. And so it's going to work it's way back up to the heart. And that's why if

  • you're on bed rest for example it's important that we move your body around because as you

  • move muscles you're actually helping to return that blood back to your heart. What is blood?

  • Well blood is made up of four things essentially. We've got red blood cells. Those are carrying

  • the oxygen. Those are carrying the oxygen around your body. We also have the plasma.

  • Plasma's going to be the liquid portion. It has a lot of the nutrients in it, but it's

  • also going to carry that carbon dioxide as bicarbonate. We have white blood cells. White

  • blood cells are going to fight infection. And then finally we have platelets. Platelets

  • are important in blood clotting so if you get a cut the platelets will form almost a

  • lattice across that cut and eventually you'll have formation of a scab. And so if you look

  • at blood, blood is going to look like this but if we let it settle out what you're going

  • to get is those red blood cells are going to be down here and then we're going to have

  • the other things continue throughout that whole of the blood, like plasma. Okay. Your

  • heart goes through what's called a cardiac cycle. Cardiac cycle is going to have two

  • parts to it. It has diastole and systole. Diastole means filling and systole means pumping.

  • And so let's say you were to take a turkey baster. So a turkey baster looks kind of like

  • this. Like that. And so basically what you do is you squeeze the bulb down here and so

  • that's like systole. You're squeezing it and the liquid would flow out. And then when you

  • relax it, it's going to suck that fluid back into it. And so if you're basting a turkey

  • that works great. So how does a heart work? Well it's going to have a systole as well

  • when it contracts and then it's going to have a diastole where it's relaxing. And so we

  • have to time it as well. Because if the whole thing were to contract that wouldn't work.

  • And so basically what you have is you have systole up here, so you're contracting the

  • atrium and that pushes it down into your ventricle. You're ventricle at that point would be relaxed

  • and then as we pump our ventricle it's going to move it back in this direction and we're

  • going to have relaxation of the atrium so we can get new blood flowing into it. And

  • so what you hear in a heart is that lub dub, lub dub, lub dub, lub dub. And why do you

  • hear that? Well you're getting that contraction of the atrium. And then they relax. And then

  • contraction of the ventricle. And the ventricle is more powerful because it has to push it

  • into the lungs or it has to push it to rest of the body. And so it's going to be way more

  • muscle that we have down here in the ventricles than we do in the heart. And we're going to

  • have way more on the left side because that has to push it all the way around the whole

  • body. So timing is important as well. So basically you have this sinoatrial node, or the SA node,

  • and what it's going to do is this is where the heart contraction is going to start. So

  • you can imagine here is our heart, let me draw it in so you can kind of look at it.

  • So we've got that. We've got our atriums. And then we've got our ventricles here. So

  • we've got our atriums and then we have our ventricles here. So basically what's going

  • to happen is you're going to start the contraction at the top of the heart and it's going to

  • squeeze the atrium shut, so we're going to get a flow of electricity in contraction,

  • pushing it down like that. But then what happens is that electrical signal will go all the

  • way down here to the apex of the heart and then we're going to get it flowing in the

  • other direction. So now we have that flow going up to the ventricle because we want

  • to move that blood remember from the atrium to the ventricle. And then the ventricle either

  • out to the pulmonary artery or out to the aorta. So it goes to rest of the body. And

  • so that's an electrical signal that does that. Now your heart, as I said at the beginning,

  • continues to beat your whole life. But it's a muscle and it needs oxygen and it needs

  • nutrients as well. So how does it get those? Well we have what are called coronary arteries

  • that are on the outside of your heart. And those coronary arteries are going to serve

  • all of the muscle inside the heart. And if we ever have a blockage inside one of those,

  • what's that going to do? Well, we're not going to get nutrients and oxygen to that part of

  • the body and so that part of the body is going to die. It's not going to be able to do it's

  • job. An so what is a heart attack? A heart attack is simply when you have blockage in

  • the vessels that serve the heart. And so the heart muscle can die. And that's why it's

  • super important that we take care of our heart. We keep our vessels very very clean because

  • we need our heart to beat our whole life. And I hope that's helpful.

Hi. It's Mr. Andersen and I was just checking my pulse to make sure that

字幕與單字

單字即點即查 點擊單字可以查詢單字解釋

B1 中級 美國腔

循環系統 (The Circulatory System)

  • 185 27
    jm117 發佈於 2021 年 01 月 14 日