Lesson video

Hello there, and welcome to today's lesson.

I'm really looking forward to working with you again today.

So today's lesson is called the Structure of the Cardiovascular System, and it comes from the Anatomy and Physiology: The Cardiorespiratory System unit.

In this lesson, we're gonna be exploring what the names of the different chambers are within the heart, and how blood circulates around the body.

So I wonder, do you know already, perhaps from science, any of the key terms or any of the names of the chambers of the heart? And also do you know any of the names of perhaps some of those vessels that blood is circulating around the body? So have a little think about that.

And also in today's lesson, we're really helping you understand how that mechanism of the heart works, and why it's so important to us as sports performers, so that we can run around and play sport, et cetera.

Okay, so by the end of today's lesson, you're gonna be able to describe the pathway of blood through the cardiovascular system, and explain its importance in maintaining blood circulation during performance in physical activity and sport.

The key words for today's lesson, again, there's a real collection here, but atria, ventricles, valves, pulmonary circulation, and systemic circulation are some of the key ones.

So you might wanna pause the video now and make a note of these, but we'll definitely be revisiting all of them in slow motion through the lesson.

So without further ado, here we are then, the structure of the cardiovascular system, and this lesson is split up into two parts.

The first part will be helping you understand the functions of the cardiovascular system, and then the second part, we'll start to explain that pathway of blood through the heart, and also starting to think about how it travels around the body.

Let's get going then.

So the heart is responsible for pumping blood around the body, and it's a big lump of muscle, isn't it? About the size of a clenched fist that sits in here in your chest cavity, nestled into your left lung.

So it delivers oxygen to the body, and when I say body, I guess I mean the muscles, so the working muscles, and provides that oxygen, so that aerobic respiration can take place.

Meanwhile, it will remove waste products, including carbon dioxide.

So we know that during aerobic respiration, oxygen is broken down to provide energy for exercise, and a byproduct of that is carbon dioxide, which we're gonna need to get rid of.

So this is why the cardiovascular system works so closely with the respiratory system, because the respiratory system gets that oxygen into the body, and the carbon dioxide out of the body, and meanwhile, our cardiovascular, cardio meaning heart, vascular meaning blood vessels, also sometimes referred to as the circulator system, is responsible for getting that oxygen and other nutrients around the body.

So yes, the heart does pump blood, carrying oxygen and carrying carbon dioxide, but it also carries other nutrients, like glucose, around the body.

The blood is also really important for clotting open wounds, to help stop us from bleeding if we cut ourselves.

For example, if you grazed yourself playing a football match on a slide tackle perhaps.

And then also the cardiovascular system has a really important role in regulating our body temperature.

It helps keep us cool in hot weather, or if we're doing exercise, and it helps keep us warm in cold conditions.

Okay, so Lucas is wondering then why is oxygen delivery so important for us to exercise? Well, I've touched on this a little bit already, haven't I? And he's also wondering, what about body temperature regulation? Why is that such a challenge for us? And then Sam's thinking, well, which body system or systems does the heart work together with to deliver oxygen? And I've given you a few clues to this already.

Yes, so the cardiovascular system is made up of two parts.

So cardio, which means heart, it's your cardiac muscle, and then vascular, meaning blood vessels, and we can see the red ones there that are, when we illustrate 'em like this, that tends to be your arteries, and the blue ones, which tend to be your veins, which are returning blood back to the heart at a lower pressure.

So the cardiovascular system is responsible for circulating blood around the body, and it's also known as the circulatory system because it circulates that body.

That makes sense, doesn't it? So just to summarise, the cardiovascular system is made up of the heart.

The blood vessels are either arteries, capillaries, and veins, and the blood, and the blood we know is made up of a few different constituents or parts, so red blood cells, white blood cells, plasma, and platelets, that we can delve into in a different lesson.

But the cardiovascular system works really closely with the respiratory system.

So the respiratory system is what brings oxygen into the body, and it's the bit that gets carbon dioxide out of the body using the lungs, and I guess the respiratory tract, so your trachea and up and through your nose and mouth, and that enables gaseous exchange to happen at your lungs.

So at the alveoli, those little air sacks in your lungs, that's where gaseous exchange occurs.

So oxygen diffuses into the bloodstream whilst carbon dioxide diffuses out of the bloodstream into the alveoli to be breathed out.

So the heart, the blood vessels, and the lungs can sometimes be referred to collectively as the cardiorespiratory system, but often, we narrow your focus on a particular part of it.

So we would tend to talk about the cardiovascular or the respiratory, but it's important to know how they work together as a whole ecosystem.

And of course, once that oxygen and the nutrients have arrived at the muscle site, they provide that energy for muscular contractions to happen.

So that's the point at which your musculoskeletal system takes over.

Okay, so when we're exercising or playing sport, we need a constant supply of oxygen to provide the energy to keep moving.

So we've got an example here of Keely during a 1500 metre race, and that's an event that really demands lots of oxygen delivery.

However, even if you're sitting at rest, so me right here now doing this recording, I still need a constant blood supply to keep my living tissues, so all of my body alive, and that includes my brain.

So you'll always get a constant blood supply to your brain.

And then during exercise, you perhaps redistribute some blood from your digestive system to get more to your working muscles, and again, we can explore that in more depth in a different lesson.

So we're getting oxygen into the body.

What was it I said we need to get out of the body? That's right, carbon dioxide, or CO2, because that's a waste product of aerobic respiration.

If we don't remove that carbon dioxide, it can cause a number of detrimental effects.

So it can cause shortness of breath, can cause dizziness, it can cause fatigue and weakness, and it can also cause impaired performance.

So actually it's almost that carbon dioxide poisoning of too much carbon dioxide in our body that we really want to avoid during exercise.

Okay, lots of information already in today's lesson.

So let's just pause for a moment, and check.

Which of the following body parts makes up the circulatory system? Is it A, the heart and lungs? Is it B, the heart, blood vessels, and blood? Is it C, the heart, blood vessels, and lungs? Or is it D, the muscles, bones, heart and lungs? Have a little think.

That's right.

It's B, isn't it? So the circulatory system or the cardiovascular system is the heart, the blood vessels, i.

e, the arteries, capillaries, and veins, and the blood, which is made up of four different constituents or four different parts to the blood.

Okay, so let's have a little think about this heat regulation element.

So when we exercise or play sport, we also generate lots of heat, and that's because we're actually not that efficient.

So when we're breaking down glucose and oxygen in our muscle sites to provide energy for muscular contraction to happen, about 80% of the energy that's gone in gets released as heat actually.

So it generates lots of heat.

That's why we get really hot when we're playing sport.

And that's a problem, isn't it? Because we don't want the body to overheat.

Homeostasis is that fancy word for the body wanting to try and keep regulated at the same core body temperature.

And the way we do that is we sweat to help regulate our body temperature.

So by sweating, that water vapour evaporates from our skin, and it takes heat away with it.

It's why sometimes if you go out on a, if you went out for a run on a really cold day, you can almost see steam coming off your skin's surface, and that's your body cooling down, and that comparison to your very hot body and the cold surroundings, and it's obviously much harder to get rid of that excess heat in hot conditions.

Also, the blood plays another really important role in that if you cut yourself, it's the platelets in the blood that work really hard to clot the blood and help you heal.

I'm sure we've all had cuts when playing sport, but also perhaps just when playing in the playground, et cetera, and it's the platelets that quickly get sent to that site of the injury to clot up and scab over, and stop you from breathing.

Sorry, bleeding.

They don't stop you from breathing at all.

Okay, so one thing to highlight at this point is lots of people get confused when they're trying to identify the left and right sides of the heart, and that's because the left side is nearest your left armpit.

So anatomically, my left side is within my body here.

However, when we're looking at a diagram on a piece of paper, that appears to be on the right-hand side due to it being a mirror image of what we're looking at.

So if I bring up the first illustration here of the heart, we can see there it's got a blue half and a red half.

I wonder if you can figure out from what I've just said, the red half, is that the left or the right side of the heart? Sometimes I almost turn myself round and into the page to figure that out.

And actually, yes, the red half is the left side of the heart, and can you figure out why it's coloured in red in this illustration? Okay, so the heart contracts.

In this, it contracts, it squeezes blood out, and the left side of that heart is receiving oxygenated blood from the lungs.

So we can see red oxygenated blood coming from the lungs into the heart, and then that red oxygenated blood will then get pumped out to the body, and delivered to the working muscles.

In this example, this hurdler.

Meanwhile, deoxygenated blood, which in this diagram is blue, so blood that's depleted of oxygen, and it'll be carrying carbon dioxide instead, that returns to the heart through the veins, and it returns into the right side of the heart.

As we look at it there, it's the reverse, isn't it? So it returns into the right side of the heart before being pumped out again to the lungs where we can breathe out carbon dioxide and pick up fresh supplies of oxygen, which makes the blood more of a rich red colour.

So let's do another quick check.

People often get confused when labelling the sides of the heart.

Which of the following is correct? Is it A, the left side of the heart is nearest your left armpit? It's actually on the right side when you look at it on a diagram on paper.

Or is it B, the left side is nearest your right armpit? It is correct when you look at it at a diagram on paper.

Or is it C, you can label the left and right sides either way.

It doesn't matter.

Have a little think.

That's right.

It's A, isn't it? And actually it's really important that we label them correctly.

Imagine going in for open heart surgery and then doing surgery on the wrong side.

Yep, so it's really important that we always label the left side, the oxygenated side, as nearest the left armpit.

And then we've got this septum, which is the muscular wall at the middle of the heart, and the job of the septum is to stop that oxygenated, in this diagram, red, rich, red colour blood from mixing with the deoxygenated blood, which we've illustrated here as being a blue.

It's a duller colour.

So it stops that blood from passing between the two halves of the heart, and that's why we often talk about the heart as working in a double circulatory pump, or a figure of eight pump, where one circuit goes to the lungs, another circuit goes to the body, and those left and right sides are both contracting to enable blood to go in the different directions.

So we call that a cardiovascular system loop or circuit, and the one that goes up to the lungs and back again, we refer to as the pulmonary circuit.

So pulmonary is a word that we associate with the lungs.

So the pulmonary circuit takes blood, deoxygenated blood, up to the lungs, and then brings it back as oxygenated blood to the left-hand side of the heart.

Meanwhile, the second loop or circuit is called the systemic circuit, and that operates between the left side of the blood, sorry, the left side of the heart, out to the body, and then returning into the right side of the heart as deoxygenated blood for the working muscles and organs.

Let's do another quick check.

So true or false? The pulmonary circuit carries blood from the heart to the body to supply oxygen for respiration.

Is that true or false? That's right.

It's false, isn't it? And can you explain why? Good.

So the word pulmonary relates to the lungs.

That's how we remember it.

So hence the pulmonary circuit carries deoxygenated blood to the lungs to collect oxygen, whereas the systemic circuit carries that oxygenated blood around the body.

Okay, that brings us to our first task for today's lesson.

So Jacob's asking, why are some of the blood vessels on the diagram shown as red whilst others are shown as blue? Well, we've talked about that, haven't we? And Aisha thinks, is it something to do with oxygen content? So the task I'd like you to do is figure out whether Aisha is right or not, and with the help of a diagram, can you label the pulmonary and systemic circuits, and then colour in the red and blue vessels with a sentence to explain their colour, and why you've coloured them that way.

If you don't have red and blue colours, then you could just write the word red, red, red, red, red, and blue, blue, blue, blue, blue on the two different parts to that circuit.

Pause the video now and come back to me when you are ready.

Okay, let's see what you came up with.

So hopefully, you've drawn a diagram a little bit like this, and these are tough because obviously the heart is a 3D feature, and we've tried to draw a cross-section of it here and simplify it.

But the important things to note are the pulmonary circuit carries deoxygenated blood to the lungs to collect oxygen, and then return to the left side of the heart.

So notice that it starts off blue, the first half of the pulmonary circuit, and comes back red.

And then, meanwhile, the systemic circuit, so the second part of that loop, the bottom of the figure of eight, carries oxygenated blood, so rich red colour, to the body, and then returns deoxygenated blood to the right side of the heart, and that loop just keeps happening.

For as long as we're alive, it will keep circulating, and it circulates faster during exercise, but it certainly gets that blood around the body really regularly.

Okay then.

So let's move into the second part of today's lesson, where we're gonna explain that pathway of blood through the heart in a little bit more detail.

So here, we've got that diagram of the heart, and you can see the blood flow through it.

So the oxygenated blood in that left side, which is red, and the deoxygenated blood in the right side, which is blue in this diagram, and the top two chambers are called the atria, or when we refer to them singularly, the left and right atrium.

So I've labelled them there for you, those top chambers.

In different drawings, I guess the layout of it is slightly different, so you need to think carefully if you're trying to label somebody else's diagram.

And then blood enters the heart through those atria, and flows down into the bottom two chambers, which are called the ventricles.

So we've got the left and right ventricles there.

So blood enters through the atria, and then travels down into the ventricles, and then from the ventricles, it's ejected out of the heart into the pulmonary or systemic circuits.

Okay, so it comes in through the atria, down into the ventricles, and then is ejected out of the heart to go either to the lungs or around the body, depending on which side of the heart it is.

So which of the following chambers highlighted in red represents the left atrium? This is a nice little check to see if you're keeping up with this.

So is it A, is it B, or is it C? So which one has the left atrium highlighted in red? That's right.

It's B, isn't it? So that top chamber is an atria, and the one on the left actually on the paper looks on the right 'cause it's a mirror image.

So we've mentioned the septum already, but here we're illustrating a little bit better that muscular wall down the middle of the heart, and I said, didn't I, that it prevents oxygenated blood in the left side of the heart from mixing with deoxygenated blood in the right side of the heart.

And if you've ever come across anyone who's got that medical condition of a hole in the heart, what that is is a microscopic hole in the septum, that means there's a little bit of seepage of oxygenated blood through one way and deoxygenated blood through the other way.

So as a consequence, if you've got a hole in your heart, you're not as efficient, and perhaps some of that endurance activity might be a little bit more dangerous or a little bit more challenging for you.

And then we also have valves in our heart, and they play a really important role in preventing the backflow of blood, so they help keep the blood pumping in the right direction.

If we didn't have these valves, blood would come in through the atria, travel down into the ventricles, and then when the heart contracts, it might squeeze back up through the atria, and out the wrong way through the heart.

So these valves prevent that backflow.

They make the blood always flow in the right direction, and they've got specific names.

So the tricuspid valve is on the right side of the heart, and I remember that 'cause there's the word, sorry, the letter R in tricuspid, and it's on the right side of the heart.

And then we've got the bicuspid valve, which is on the left side of the heart.

Another nice way to remember that is that we often try before we buy clothes, don't we? So tri comes first.

So when you're reading it across the page, tri first, bi next.

Okay, and then we've also got valves on the exit from the ventricles, and they're called the semilunar valves.

So as the blood is pumped out into the pulmonary circuit and into the systemic circuit, we've got these semilunar valves that close off once the blood's been pumped out to stop it at high pressure from coming back into the heart the wrong way.

'Cause, obviously, we want to get it round in the direction that's useful to us.

So let's do another quick check.

Which of the following statements is incorrect? Is it A, valves in the heart prevent backflow of blood? Is it B, valves are between atria and ventricles, and on the exit of the heart into the main arteries? Or is it C, valves prevent oxygenated and deoxygenated blood from mixing? Or is it D, valves in the heart are forced open due to increasing pressure? Have a little think.

Process of elimination here, maybe.

That's right.

It's C.

So it's actually the septum, isn't it, that prevents oxygenated and deoxygenated blood from mixing.

And I perhaps didn't cover in enough detail how important those valves are, that they start off closed, and as blood pressure builds up in the atria, that's what forces the atrioventricular or the tricuspid and bicuspid valves open to enable that blood to come down into the ventricles.

And then as it flows down, that'll then close off, and then the pressure builds and builds and builds in the ventricles until the point where the semilunar valves are forced open, and the bottom of the heart squeezes and pumps the blood up and out of the ventricles.

So I have another quick check then.

I've mentioned the tricuspid and bicuspid valves, but true or false? The tricuspid valve is between the atrium and the ventricles on the left side of the heart.

That's right.

It's false.

Can you remember why? Yeah, because we tri before we bi, don't we? The tri has an I in it, tricuspid, which means it's between the right atrium and the right ventricle.

As you look at it on the page though, it's actually on the left side, which is why lots of people use that nice reminder of you tri before you bi as you read them on the page.

Okay then.

So if blood first enters the heart from the lungs into the left atrium, it comes in through a vein called the pulmonary vein.

So pulmonary in connection with the lungs, vein because it returns blood to the heart, and blood exits the left side of the heart through the aorta.

So the aorta is the biggest artery in the human body, and it branches off to all the different parts of the body, except for the lungs actually.

They have their own separate supply.

But interesting fact, the pulmonary vein is the only vein in the human body that carries oxygenated blood 'cause it's bringing it from the lungs back to the heart, whereas every other vein is carrying deoxygenated blood.

And then once that blood has been around the body and delivered oxygen to the muscles, to the digestive system, into the brain, et cetera, et cetera, deoxygenated blood returns to the right side of the heart in through what's called the vena cava or vena cava.

And in fact, there's an inferior and superior vena cava, one from the bottom part of your body and one from the top part of your body.

So sometimes we see this diagram with a couple of branches on it.

And then after the blood has come in through the right atrium and down into the right ventricle, it is then pumped out through the pulmonary artery.

Okay, and as I mentioned earlier, there's quite often different illustrations of this that you can come across.

So you can see a 3D illustration, and you can see that vena cava, it's got the superior/inferior pipes coming in, one from the upper body and one from the lower body behind the back of the heart there.

But what about this one on the right-hand side? Can you have a go at labelling the chambers on that one? Which one do you think the aorta is, and which one do you think the vena cava is? That's right, so the vena cava is that one in the back there.

We've also got the pulmonary artery and the pulmonary vein.

There's the aorta.

It actually loops up around the top of the heart, and then down to feed the body.

So have a look at a few different illustrations to see how the different pipes enter and exit the heart.

Okay, let's take a quick check then.

Which of the following returns deoxygenated blood from the body? Is it A, the pulmonary artery, B, the pulmonary vein, C, the aorta, or D, the vena cava? Have a little think.

That's right.

It's D, the vena cava.

So it's the vena cava that brings deoxygenated blood back into the right side of the heart.

So that brings us into our next task.

So I'd like you to fill the gaps and label this diagram that we looked at earlier, but to represent the pathway of oxygenated blood from the lung.

So I've labelled up A is where the blood starts, at the alveoli, at the lungs, and they collect oxygen.

So what is that vessel called at B? What about the one at C? What about the.

So C is the left atrium.

Can you draw an arrow to where that is? What about the bicuspid valve? Where's that? Draw an arrow.

What's label E pointing at? And then F is the semilunar valve, G is the aorta, and H is the body.

Can you label those ones up? And then the second part of this, I want you to label, I've actually flipped the table on the left-hand side here, so you'll see the letters.

It starts at the body, and then works up from the body up through what, through what, into the tricuspid valve, into the right ventricle, into the semilunar valve, through what, to end up back at the lungs, and then the whole system repeats itself.

So finish off labelling the missing letters that the arrows are pointing at, and add arrows for the ones that have already been labelled for you.

So pause the video now whilst you do that, and come back to me when you are ready.

Okay then, so I filled the gaps here.

Did you manage to get these correct? And then let's have a look.

So we've got the lungs to collect oxygen.

We've got the pulmonary vein there, turning blood from the lungs.

Got the left atrium, through the bicuspid valve, to the left ventricle, through the semilunar valve, to the aorta, and then through to the body.

And then on the other side of the heart, we've got the body, up through the vena cava, so the superior and inferior vena cava, into the right atrium, through the tricuspid valve, into the right ventricle, through the semilunar valve, into the pulmonary artery, and then on up to the lungs.

So that's that circulatory system in action.

Well done if you've kept up with me on that one.

There's a lot of new terminology in this lesson and new things to think about.

So just to summarise then, the cardiovascular system transports oxygen, carbon dioxide, and nutrients.

It also plays an important role in clotting the blood and regulating our body temperature.

Deoxygenated blood travels from the right ventricle of the heart to collect oxygen from the lungs, and returns via the left atria, and that's called the pulmonary circuit.

Meanwhile, oxygenated blood travels into the aorta from the left ventricle.

It then delivers oxygen to the working muscles, and it will return into the right atria, and that circuit is called the systemic circuit.

And then we've also got to remember, haven't we, that valves in the heart open due to pressure.

When the pressure builds up, that forces the valves open, and then they close off to prevent the backflow of blood.

And we talked about the tricuspid, bicuspid, and semilunar valves in today's lesson.

Hope you've enjoyed that today.

I have, and I look forward to seeing you again next time.