Lesson video

Hello there and welcome to today's lesson.

My name's Mr. Sues and I'm really looking forward to teaching you today.

So today's lesson is the structure of the heart and it comes from the anatomy and physiology: the cardio respiratory system unit.

In today's lesson, we're gonna unpick what the different chambers of the heart are called and how the heart operates to circulate around the body.

Have you ever wondered what is it that the heart's doing and why is it so important for life but also for physical activity in sport? Okay, so by the end of today's lesson, you're gonna be able to describe the pathway of blood through that double circulatory system and explain its importance in maintaining efficient blood flow.

We're gonna be covering a whole load of new keywords today, some of which you might have come across in science or maybe through your own general interests you've come across these different words like the atria or atrium, the ventricles, the valves, the pulmonary or systemic circuits.

But these are likely to be new to you, so you might wanna pause the video now and make a note of them, but we'll definitely be revisiting them during the lesson and I'll give you plenty of time to make a note and recall what each of them is.

So in today's lesson we're gonna break it up into two parts.

The first part will help you understand how the double circulatory system works, and then in the second part we're gonna explain that pathway of blood through the heart and through the body.

Okay, well if you didn't know it already, the heart is responsible for pumping blood around the body.

It's about the size of a clenched fist and it's here in our chest, nestled into our left lung.

And it pumps blood around the body in order to deliver oxygen to the working muscles and also to remove waste products such as carbon dioxide from the working muscles.

Well, why is oxygen delivery so important to us for exercise? And which body systems does the heart work with to deliver oxygen? Maybe pause the video briefly while you have a think about those two questions before we unpick them further.

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

Cardio, meaning heart, and vascular, meaning blood vessels.

And those blood vessels are called the arteries, the capillaries and the veins.

And you might have come across those words before and we definitely cover that in more detail in a different lesson.

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

So watch out for the CV system, cardiovascular or the circulatory system meaning the same thing.

So just to summarise then, the cardiovascular system is made up of the heart, that cardiac muscle that's beating away in your chest, the blood vessels, so the arteries and the capillaries and the veins, shown with those little red and blue threads on the diagram here.

And then the actual blood.

So the constituents, the makeup of the blood, there's four different parts, red blood cells, white blood cells, platelets and plasma.

And again, we'll explore those in a bit more detail in a different lesson.

So the cardiovascular or circulatory system works really closely with the respiratory system.

Can you figure out why? That's right, so the respiratory system brings oxygen into the body, (teacher breathing deeply) in through our nose and mouth, down through our trachea into our lungs.

And then it's alveoli that gaseous exchange occurs.

So that's where oxygen will diffuse into the bloodstream and carbon dioxide will diffuse outta the bloodstream into the alveoli to be breathed out again.

And it's from that moment there where the capillaries that surround each alveoli are coming into contact to enable the oxygen to diffuse into the blood and then the blood can carry that oxygen back to the heart.

And then the heart, blood vessels, and lungs can sometimes be collectively referred to as the cardio respiratory system.

So another key term to watch out for.

And interesting to connect this now with the other body systems. So once oxygen and nutrients have arrived at the muscles, they provide energy for exercise and at that point the musculoskeletal system will take over.

So the muscles would grab hold of that oxygen and they'll break it down for aerobic respiration to enable muscular contraction to happen.

And when the muscular contraction happens, the muscles pull bones at joints for movement to occur.

So that's why these four body systems work together so closely and we study them in GCSE PE.

Okay, so if you were exercising or playing sport, you would need a constant supply of oxygen to provide that energy to keep moving.

We've got a picture here of Keely as she's running a 1500 metre race which puts huge demand on oxygen delivery to the muscles to beat the other competitors.

However, even at rest we need a constant blood supply.

That's why we keep breathing and our heart keeps beating even when we're asleep.

And that's to keep our living tissues alive and that of course includes the brain.

That's the last place we want to starve of oxygen.

And then carbon dioxide or CO2 as it's known, is that waste product of respiration.

So that's produced in your muscles and then it gets shipped into the bloodstream to get carried back to the heart, then back to the lungs so we can breathe it out.

It's why we've got this great symbiotic relationship with trees because they do the opposite to us in terms of oxygen and carbon dioxide.

So if we don't remove that carbon dioxide though, it can cause some pretty damaging side effects.

So it can cause that shortness of breath, can cause dizziness, it can cause fatigue and weakness.

And ultimately that means that you will have an impaired performance.

So we sometimes even talk about it as being carbon dioxide poisoning.

We've got too much carbon dioxide in the body and we need to get rid of it.

Let's do a quick check then.

So 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.

Well done, hopefully you put B, the heart, blood vessels and blood that make up the circulatory system.

And then just at this moment I think it's important to flag that identifying the left and right sides of the heart can be confusing at times.

And the way I like to remember it is the left side is the side nearest the left armpit.

So the left side of the heart is nearest the left armpit.

However, when we're looking at diagrams of that down on paper, it appears on the right hand side.

So it's almost a mirror image of that.

So if we bring up an illustration then of the heart, we can see here that the red side of that heart, it's coloured in red because it's oxygenated blood and that's actually the left side of the heart.

It's nearest the left armpit, if we almost reverse me onto the page, you'll see that's the left hand side of the heart.

And that's why there's sometimes that confusion of labelling left and right sides.

Anyway, so the heart's job is to contract and squeeze blood out of it.

The left side of the heart receives oxygenated blood from the lungs and it pumps it out to the body.

So that left side of the heart that's coloured in red is dealing with oxygenated blood.

And meanwhile deoxygenated blood, and we illustrate that with blue on the diagram, it returns from the body so that's depleted of oxygen and it's full up of carbon dioxide in its place.

It returns to the right side of the heart before then being pumped back out to the lungs one more time.

And you can see there that kind of double circulatory pump that we'll explore in a bit more detail in a moment.

But before we do that, let's do another quick check.

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

Which of the following is correct? Is it A, the left side is nearest the left armpit.

It's actually on the right side though when you look at it on a diagram on paper.

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

Or is it C, you can label the left and right sides either way? What do you think? Well done, A is correct and of course it's really important that we label them correctly, otherwise we could have someone going in for open heart surgery where they've got a problem perhaps with the left side of their heart and the surgeon operates in the wrong place.

So really important that we label it up correctly.

And then we've got another important feature which is the septum, which is a muscular wall up the middle of the heart there.

You can see it in kind of black down the middle, separating the blue and the red sides.

And the job of the septum is to prevent oxygenated blood, on that left side, from mixing with deoxygenated blood on the right side.

So it does that in order to form this kind of network of blood vessels that look like a figure of eight.

And if we didn't have a septum, and of course we all have a septum, but occasionally we have a bit of a defect where people could have a hole in the heart and that means they've got a microscopic hole between the left ventricle and the right ventricle typically.

And it means little bits of blood can pass backwards and forwards through there and it means that perhaps they're not as efficient because that oxygenated blood might leak into the deoxygenated side.

But more importantly, the deoxygenated blood might leak into the oxygenated side, meaning that you're pumping blood around that isn't fully charged with oxygen.

So if you've got a hole in your heart, you might struggle to do really high intensity endurance exercise.

Okay, so I've said, haven't I, that there's a double circulatory system that's operating as two loops.

And the top loop that goes to the lungs is called the pulmonary circuit.

Pulmonary is a word we always associate with the lungs.

So pulmonary circuit between the heart and the lungs.

And then the second loop is called the systemic circuit and that operates between the heart and the rest of the working muscles or organs of the body.

So another quick check then.

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? Can you explain why? Well done, so the word pulmonary relates to the lungs, doesn't it? So hence the pulmonary circuit carries deoxygenated blood to the lungs to collect oxygen, whereas it's the systemic circuit that carries blood to the body systems. Okay, so Lucas has got a question for us, "Why are some of the blood vessels on the diagram shown as red whilst others are blue?" And Aisha thinks, "Is it something to do with oxygen content?" Well I wonder, can you figure out for this practise task, is Aisha right? And with the help of a diagram can you firstly label the pulmonary and the systemic circuits and then secondly colour in the red and blue vessels with a sentence to explain why you've coloured them in the way you have.

If you don't have a red and blue pen, you could just write red, red, red, red, red, blue, blue, blue, blue, blue to the corresponding bits of pipe work.

Pause the video now whilst you do that and come back to me as soon as you are ready.

Okay, let's have a little look then.

So hopefully you've come up with a diagram a little bit like this.

And with that diagram you're gonna have identified that the pulmonary circuit is that top loop, the one that's supplying deoxygenated, so blue, blue, blue, blue, blue blood to the lungs and then red, red, red, red, red blood back to the left side of the heart.

And meanwhile the systemic circuit is that lower loop that carries oxygenated or red blood to the body and then it returns deoxygenated or blue blood to the right side of the heart.

Did you get that one correct? Occasionally we have people mistaken and thinking all of one loop is red and all of one loop is blue.

So just check your diagram carefully.

And then blood vessels that carry oxygenated blood are shown in red, whereas those carrying deoxygenated blood are shown in blue.

So that's that explanation that I was asking you for.

Okay, then let's move into the second part of this lesson where we're gonna explain the pathway of blood through the heart and around the body.

So what are some of those chambers called? Here we've got our diagram of the heart again, and I wonder, could you label any parts of this? That's right, we are returning to some of those keywords of this lesson, aren't we? So the atria, when they're referred to collectively or the left or right atrium when we refer to them as in the singular.

So the left atrium is that top chamber on the left hand side of the heart.

And the right atrium is the top chamber on the right hand side of the heart carrying deoxygenated blood.

Then we go down into the bottom chambers and the ventricles.

Again, we've got the left ventricle connected with the left atrium carrying oxygenated blood and the right ventricle connected with the right atrium carrying deoxygenated blood.

So the ventricles are the bottom two chambers.

And blood is ejected from the ventricles into the pulmonary or the systemic circuits depending on which side of the heart it is.

So let's do a quick check before we delve deeper.

Which of the following chambers highlighted in red represents the left atrium? Is it A, is it B, or is it C? Well done, it's B.

That top chamber on the left hand side, but as we look at the diagram, it's actually on the right, isn't it? So it's the mirror image.

And I mentioned this already, but there's a nice closeup here of that septum wall, the muscular wall that's down the middle of the heart that serves a really important job or role in preventing oxygenated blood on the left side from mixing with deoxygenated blood on the right side.

We're gonna move on now and have a look at some of the valves within the heart that help prevent backflow and also help keep blood pumping in the right direction.

And as blood pressure rises, these valves are forced open and then the close off to stop blood from coming back in the wrong direction.

So we've got valves there between the atria and the ventricles, and then we've also got valves on the exit of the ventricles into the main arteries, the artery that supplies the lungs and the artery that supplies the body.

So we've got four different valves in the heart that close off as blood moves past it, and then a forced open due to pressure increases.

All right, so they open up due to a pressure buildup and that lets the blood flow down from the atria into the ventricles and then the pressure will build up in the ventricles until that valve on the exit of the ventricles is forced open.

Once they've been forced open, the blood flows out at high pressure and then they close off to stop that blood from coming back in the wrong direction.

Okay, let's do another quick check.

So 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? 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? So I'm wondering which one of those is incorrect? That's right, it's C, isn't it? So actually it's the septum, the muscular wall up the middle that prevents oxygenated and deoxygenated blood from mixing, whereas all the others were true.

Let's do a true or false one then.

So valves are only present between the atria and the ventricles in the heart.

Is that true or false? That's right, it's false, isn't it? And can you tell me why? Where are the other valves in the heart? That's right, so there's the valves between the atria and the ventricles called the atrioventricular valves or the tricuspid and bicuspid if we refer to them by their singular names.

And then there's also valves on the exit from the heart into the arteries and they're known as the pulmonary valve and the aortic valve or their semilunar valves.

But thankfully, unless you wanna become a physician one day and operate on hearts, you don't need to know the names of those different valves.

But what you do need to know is that they're forced open when pressure rises and that ejects blood into the next passageway.

So if blood first enters the heart from the lungs via the pulmonary vein, this is oxygenated blood coming from the lungs into the heart via the pulmonary vein and it then goes through the left atrium, through a valve, into the left ventricle, up through a valve and out through the aorta.

So it's the aorta that carries blood off around the body.

So the aorta is the biggest artery of the human body.

It carries blood everywhere except for the lungs.

And then meanwhile we've got deoxygenated blood that's returning from the body and it comes in through the vena cava or the vena cava.

And it goes in to the right atrium, down through a valve into the right ventricle, then up through a valve and out through the pulmonary artery, which of course is that artery, the only artery carrying oxygenated, sorry, deoxygenated blood and it's carrying deoxygenated blood 'cause it's on its way to the lungs to get re-oxygenated.

So the pulmonary artery is the only artery in the human body carrying deoxygenated blood.

And the pulmonary vein is the only vein in the human body that carries oxygenated blood.

I think it helps sometimes to have a look at a different illustration.

So if you look through the books or if you Google it, you find lots of different images of the heart and sometimes they're in this more 3D layout.

So you can see here how the vena cava actually is two pipes coming in through the back of the heart on that right side.

And that's because one's feeding blood from the upper body and one from the lower body.

They're called the superior and the inferior vena cava.

And I'm wondering, can you have a go at labelling this another alternative diagram on the right hand side? So I'm hoping you can see the vena cava there, again, it's kind of a white in colour.

You can see the bottom one and one coming from the top and they're feeding into that right atrium.

We've got the pulmonary artery there that is squeezing blood out of the right side of the heart.

We've got the pulmonary vein, which is feeding blood in from the lungs into the left atrium.

And then the aorta actually is that looping pipe that's coming from the left ventricle, the biggest artery in the human body.

So that's quite a tough illustration, that one.

Okay, let's do a quick check.

So which of the following returns, deoxygenated blood from the body? Is it A, the pulmonary artery? Is it B, the pulmonary vein? Is it C, the aorta? Or is it D, the vena cava.

That's right, it's the vena cava.

Okay, that brings us to our last task of today's lesson.

So I want you to have a go at filling the gaps and labelling this diagram to represent the pathway of oxygenated blood as it comes from the lungs with oxygen, back through, what's that pipe called at number two? Into the left atrium? Can you draw the arrow to where that left atrium is? Draw the arrow to where the valve is.

Then what's number five pointing at? Through another valve, can you label that number six? Out through the aorta, label that.

And then to the body.

And then I also want you to label the second half of the heart.

And I've actually numbered it from the bottom up so that there aren't so many crossed wires, crossed lines.

But from the body we come up through number 10, through number 11, through a valve, into the right ventricle, can you label that? Through another valve into what? That carries blood up to the lungs for oxygenating.

So you need to pause the video now whilst you fill the gaps and draw some arrows and I'll see you in a moment.

Well done, so let's run through these then.

So the missing words were pulmonary vein, left ventricle and we've got number one labelled there.

Number two, that main pipe in red.

The left atrium in that top chamber.

The valve, down to the left ventricle, up through another valve, out through the aorta to the body.

And then on the other side, on the deoxygenated side, we've got blood from the body, coming up through the vena cava, through the right atrium, through that valve, into the right ventricle, through another valve and out through the pulmonary artery where it can get carried to the lungs for oxygenating.

How did you do that one? Quite a tough task that one.

Okay, so there's just a little bit of time left for us to summarise today's lesson.

So the structure of the heart was the title and we've learned that the heart operates as a double circulatory pump.

And that means that deoxygenated blood travels from the right side, in fact the right ventricle of the heart where it will collect oxygen and return to the left atria.

And that top circuit is called the pulmonary circuit.

Meanwhile, so at the same time, we've got oxygenated blood that's travelling from the aorta and it's fed into the aorta from the left ventricle, isn't it? So from the aorta carries that oxygen to the working muscles of the body and then returns into the right atria.

And that is called the systemic circuit.

We've also learned that there's a number of different valves in the heart, four actually, and they open up due to pressure buildup and then close to prevent the backflow of blood.

So they help ensure blood keeps travelling in the right direction as your heart is beating.

Hope you've enjoyed today's lesson.

There was an awful lot in there, wasn't there? So I look forward to seeing you again next time.