Lesson video

Hello and welcome to today's lesson.

My name is Mr. Swayze and I'm really looking forward to teaching you today.

So we're going to be looking at blood vessels and blood cells.

We'll be unpicking the different types of blood vessels in the human body like arteries, capillaries and veins, but also the different types of blood cells.

You may know that red blood cells are the most important for us as sports performers, but why are they? And what are the other constituents of blood? Today's lesson is called Blood Vessels and Blood Cells and it comes from the anatomy and physiology for cardio respiratory system unit.

I hope you enjoy it.

By the end of this lesson, you'll be able to explain the structure and function of different types of blood vessels and blood cells in the circulatory system.

So I've already mentioned the names of some of the blood vessels and that red blood cells are really important to us, but do you know of any more? Do you know the characteristics and the functions of these different aspects of the blood and blood vessels? The keywords for today's lessons are arteries, veins, capillaries, red blood cells, and white blood cells will also be looking at platelets and plasma.

You may want to pause the video now to make a note of them, but I will explain them fully as we come across them in the lesson.

So in our lesson today, we've split it up into two parts.

The first part is helping you understand those different blood vessels.

So the arteries, the capillary is the veins, and then the second part of the lesson will be explaining the different constituents of blood, so those red blood cells, white blood cells, plasma and platelets, to help you understand the role of those different parts of the blood.

I hope you're ready.

Let's get started.

Okay, so here we've got a nice picture of the human body with all of the muscular and skeletal systems stripped out so that you can just see those important blood vessels.

And we very often see it illustrated this way, don't we, with some of those pipes as red whilst others are blue.

And hopefully you've picked up on the fact that we identify the red ones as arteries because they're the ones that are carrying oxygenated blood.

Whereas the blue ones, we typically illustrate 'em like that because they're the veins and they're carrying deoxygenated blood.

And in fact, that's not just what we do on pictures.

If you were to look at your arteries quite often they're that dark red in colour.

They're also deep in under the skin, so they're hard to see.

Whereas veins, here I am, I can see some of those blue veins at the surface of the skin in my wrist for example.

So blood vessels are those tubes then that transport blood around the body.

And there's three different types.

We've got arteries, as we've seen here in red.

We've got veins, as you can see there in blue.

And then they're really interesting ones in my opinion, are the capillaries.

So they're the ones in between arteries and veins where gaseous exchange happens.

And we can let nutrients, oxygen, carbon dioxide, move backwards and forwards through those capillaries because they're only one cell thick.

So capillaries are really the place where the action happens, whereas arteries are those ones that are carrying the blood at high pressure quickly to where it needs to be.

Capillaries are where the action happens, that gaseous exchange, and then veins are really important in carrying that blood back to the heart so it's available to be pumped out again.

And you may have heard of the term venous return, so that's your veins returning blood to the heart.

Do you know the similarities and differences between these different arteries, veins and capillaries? I'm wondering.

Okay, let's have a bit of a deeper dive into arteries first of all.

So they've got the following features.

They've got a small lumen that's the hole up the middle of that pipe.

So if you almost think of a hose pipe, one that's got a really thick rubber outside layer that helps it carry water at really high pressure and quite a narrow gauge or hole up the middle of it.

So there's a a narrow diameter up the middle.

And the reason that they're like that is because they've got that really thick muscular wall around the outside that helps to carry blood away from the heart at really high pressure without risk of I guess bursting open and the blood squirting out.

You can feel your pulse in an artery and they also vasodilate and vasoconstrict to help direct blood flow to particular places.

So if we just take for example my carotid artery, which I can feel here, I could take my pulse at my carotid artery, but also there might be instances perhaps where you want to send more blood flow for example, to your legs.

So for maybe you are on a bike and you cycling and your legs, the muscles in your legs, your quadriceps, your hamstrings and your gastric anaemia are working really hard.

So they need extra blood supply to go there.

So we will vasodilate the blood supply that goes to our legs to get more oxygen rich blood into our legs, but maybe we don't need as much blood flow going to our digestive system whilst we're cycling.

So we might vasoconstrict the blood flow that's going to the digestive system or maybe even to the arms because they're just static on the bike and less blood will go there because we obviously want to direct maximum volume of that oxygenated blood to the legs.

Okay, this is an endon view of an artery and it shows how it's got that really thick muscular wall around the outside and a relatively small lumen or hole up through the middle where the blood will be passing.

So I remember this as A for A-rteries carry blood, A for A-way from the heart and that's certainly the top tip there from Andeep.

So remember that arteries always carry blood away from the heart.

Nearly always it's oxygenated blood, but again you'll learn that there is one particular artery that carries deoxygenated blood.

Then if we move on to veins, we can tell this is a vein because it's got these little pocket valves in it.

So a number of different features that you need to know about veins are that they have a really wide lumen.

So they've got quite a big hole up the middle of them to allow free flowing blood on its way back to the heart, they've got a fairly thin muscular wall and that's because they're not operating at high pressure.

So they don't need that thick muscular wall that the arteries need.

But they also don't need to vasodilate or vasoconstrict to redirect blood to where it's needed most and instead their job is just as quickly as possible get that blood back to the heart so that it can pick up oxygen again.

But often they're running against gravity, aren't they? So if we think of those veins in our legs, they're trying to get that blood.

Maybe I was riding my bike and the veins are trying to get that blood back up to the heart as quickly as possible where they're running against gravity, which is a challenge.

So they have these things called pocket valves in them that mean that as the blood's pumped up a bit, they'll close off.

So they only let the blood travel in one direction i.

e.

back towards the heart.

And they carry that blood back to the heart at low pressure as I have said already.

And I guess is really important isn't it, that that blood gets back to the heart to be available to get pumped out again and we'll learn later today what sort of volume of blood we have in our human body and then we can connect that up with, okay, so how many times does every little blood cell circulate around the body at rest? And what about during exercise in order to do its job? Okay, let's have a quick check.

So true or false? Arteries have a thick muscular wall and a lumen.

That's right, it's true because arteries always carry blood away.

A arteries a foot away from the heart and it's at high pressure and hence they have that thick muscular wall and a narrower lumen compared to veins.

Okay, so here we've got a capillary and you can just see the edge of that red bit which is representing the artery feeding in at one end of the capillary and the blue bit at the other end.

The vein as it feeds out, we'll zoom out and see the whole picture of that later.

But for me, capillaries are the most exciting blood vessels because they are only one cell thick and the reason that their cell walls are only one cell thick is to allow the exchange of materials so oxygen, carbon dioxide and nutrients to pass out between the blood and the tissues of the body.

And that primarily is happening at the lungs and then again at the muscle sites.

So as I've said, the wall is only one cell thick now for a very narrow lumen and the job of that is to really slow down the flow of blood cells.

So there are almost single file resting their way through there is fairly slowly so that they've got time to give off oxygen and pick up carbon dioxide for example, if they're at the muscle site.

So that allows that gaseous exchange of oxygen, carbon dioxide and nutrients to happen.

As I've just mentioned, they're located at the lungs and also at the muscle site.

Okay, so here's that zoom dive picture that you might have spotted a moment ago on the capillary slide and you can see arteries, capillaries and veins and that network of blood vessels that all work together.

Okay, let's have another quick check.

So these students are discussing body systems and I'm wondering who is correct? Is it Andeep who says that, "Arteries always carry oxygenated blood." or is it Jacob who says that, "Gaseous exchange occurs in arteries." Or is it Sofia who says that, "Arteries always carry blood away from the heart." Hopefully you got that one right.

So yeah, A for A-rteries, A for A-way from the heart and Andeep is nearly right in that nearly all arteries carried oxygenated blood.

But actually, we've got the pulmonary artery that carries blood to the lungs and is deoxygenated blood going there to pick up fresh batches of oxygen, which means the pulmonary vein is the only vein in the human body that is carrying oxygenated blood.

More on that in another lesson.

So it's important just quickly to mention blood pressure.

So blood pressure is the force exerted by circulating blood against the walls of the arteries and against other blood vessels.

And we can see here this person is having their blood pressure taken using this blood pressure monitor and it's measured in millimetres of mercury or mmHg.

And when we measure blood pressure, we get a reading of the systolic pressure over the diastolic pressure.

So an average reading might be something like one 20 over 80.

So that means that there's 120 mmHg of pressure on those arteries when the heart is in its contraction phase.

And then even when it's under relaxation or diastole there's still 80 mmHg of pressure on the walls of the artery.

So it's always under quite a bit of pressure and what we have to be really careful of is looking after, you know, exercise, looking after our diet, trying to reduce stress, trying to get better sleep so that we don't have what we call hypertension, which is when that diastolic blood pressure reading goes over 100.

So you certainly wouldn't want to be regularly having a heart rate reading of perhaps, I don't know, one 40 over a hundred would be something you might want to see your GP about.

Maybe interesting at this point to help you remember that V for veins are the ones that carry valves in them or pocket valves to help that blood flow back to the heart.

And you may have heard of varicose veins that some people suffer from.

So often in elderly people, those varicose veins are when you've got swollen and twisted veins and that's caused by poor blood flow to largely the the calf area, people get the med.

So for example, if you go on a long haul flight, there's also an increased risk of what we call a deep vein thrombosis or a DVT, which is a blood clot in a deep vein usually in the leg.

So that's why it's really important that we help do things to keep blood flow into our legs going i.

e.

we get up and move and that's why when you're on a long-haul flight, you're encouraged to get up and move and stretch a bit to stop that blood pulling from happening in your legs.

So I mentioned earlier that veins carry blood at a lower pressure and often against gravity.

So that's why these pocket valves exist to help keep that blood flow back to the heart.

Let's have another quick check.

Which of the following pictures looks like a vein? Is it A, is it B or is it C? That's right, it's C that image that carries a pocket valve.

Whereas image A is an example of an artery and image B is actually an endon view of muscle fibres.

Okay, so the cardiovascular system also plays a really important role in regulating our body temperature as we can see here with this young boy sweating and going red.

So regulating your body temperature has a posh name, it's known as thermo regulation, thermo meaning heat regulation, meaning keeping it the same.

And as we probably know, our core body temperature is kept really close to 37 degrees all of the time, even if we're out skiing on the mountains where it's really cold or lying on a beach where it's really hot, our body works really hard to try and maintain a steady core body temperature and that's known as thermo regulation.

So if we were to start to exercise, particularly if we're somewhere where it's very hot, that produces heat in the body and we've gotta get rid of that waste heat.

And the way we do that is we sweat because when we sweat that moisture evaporating from our skin carries the heat away with it, it radiates that heat away but also we send more blood to the surface of our skin.

So you can see rosy cheeks and rosy skin often when people are exercising and particularly if they're exercising hard.

Okay, the first task I'd like you to do then is I'd like you to complete the following table which summarises key features of those different blood vessels.

Pause the video now whilst you do this task and then we'll have a look at the answers.

Okay, hopefully you've come back to me because you are ready to reveal the answers.

So here we go.

That first line is shown the arteries because they carry blood away from the heart, they have a thick muscular wall and the function to pump blood at high pressure.

Then secondly we've got the capillaries.

So we have those capillaries at the lungs and at the muscle tissue site they're only one cell thick and their really important job is about enabling that gaseous exchange.

So the oxygen, the carbon diox are the, the flow in and out from the bloodstream to those other parts of the body.

And then lastly we've got veins.

So they carry blood back to the heart and they contain those pocket valves to help keep that flow often against gravity to keep going and as you can see there, so their function is prevent the backflow of blood to return the blood to the heart at lower pressure.

Okay then so onto the second part of the lesson.

So we've covered off blood vessels and we're now gonna look at the different constituents or parts of the blood itself.

So blood is made up of four main parts and perhaps it's interesting to note that as an adult I have about five and a half litres of blood in my body.

So that blood is continually circling round, circulating round and round my body and if I start to exercise it circulates faster because of the different properties of blood and what they're trying to achieve.

So as I mentioned at the outset of this lesson, red blood cells are the really important one for us as sports performers 'cause they have a crucial role in carrying oxygen.

And we have about 45% of our blood is made up of red blood cells and actually if you go and train at altitude you can grow more red blood cells so it might go slightly higher than that.

Then we've got blood cells, sorry, white blood cells and less than 1% of them.

So not very many white blood cells per volume of blood.

Can you think of what the last two are? So we've got platelets.

Again, less than 1% of the blood is platelets and then plasma which accounts for about 55% of the blood in that kind of milky yellow colour that you can see in the test tube.

Okay, so let's look at these red blood cells first and you may have come across them in science where they're often referred to as erythrocytes, not a word that we need to remember for GCSCPE, thankfully.

And they're essential for sports performers because they contain haemoglobin.

That word again is haemoglobin and that's really important because it carries oxygen and when it carries oxygen it's known as oxyhemoglobin and then they also carry carbon dioxide.

So they're also capable of carrying that carbon dioxide back to the body.

And interestingly, they also carry carbon monoxide, which as we know comes from cigarette smoke.

So that's why it's really important you don't smoke if you want to do exercise because if you've got carbon monoxide being carried around by your haemoglobin, it can't carry oxygen, which means you won't be able to work aerobically or you won't be able to do endurance sport as well.

So how would our sports performers be affected if we didn't have red blood cells? And before we move on to talk about white blood cells, I guess the key thing is as a sports performer, if we didn't have red blood cells, we wouldn't have that capability of carrying oxygen to our muscles.

And if we can't carry oxygen to our muscles then we can't work aerobically.

We can't continue to move for long periods of time.

Okay, so onto white blood cells.

Again, you may have heard of these in science referred to as leukocytes and they're essential for the immune response, fighting infections and keeping performers healthy.

So again, vital for everyday healthy living but also as a sports performer.

So I've actually picked up a a achilles tendon injury and my white blood cells are doing a great job at the moment of trying to work on that muscle site and the tendon site to improve it.

And if perhaps I was unwell, maybe I've caught COVID again, the white blood cells have got a really important role in trying to fight that infection and help me recover and become healthy again.

Okay, let's move on to the third constituent of the blood, so these are known as platelets or thrombocytes and they are essential for clotting the blood, repairing wounds.

For example, cuts and grazer and I guess we need to think of these as like little disc shaped cell fragments and they circulate around in the blood and yeah they pay that massively important role in blood clotting.

So if for example I fell over and I grazed my knee perhaps playing football, my body would very quickly respond and these platelets that are created in your bone marrow will circulate around in your bloodstream.

They'll make their way to where that injury has happened.

So where that open wound is and the platelets are kind of those first responders so they adhere to the site of the injury and then they start to change shape which allows them to better connect to each other and the damaged blood vessel wall and then they forming a clot to the point where they plug that damaged area so there's no longer a hole that's allowing that blood out of the the artery or the capillary or the vein and that then stops it from bleeding and then that wound will get repaired.

So again, platelets are an essential part of our repair system.

And then onto the last one then we've got plasma which makes up the majority of the blood volume.

So it's a yellowish fluid and it contains mainly water but also electrolytes, proteins, hormones and other waste products and it's essential for that blood flow.

So if we didn't have that large volume of plasma, so if we don't stay hydrated so that we've got lots of water in our system that can be absorbed into the bloodstream to mean that we've got a good volume of blood, we can't keep that blood flow as fast as we need it to be.

So when we sweat we actually start to lose some of that plasma volume to help us cool down and that helps regulate our blood temperature but will result in our blood pressure increasing.

So that's why we've gotta keep taking fluids on in long distance events.

Okay, so which of the following fights infection, is it A, red blood cells.

B, white blood cells or C platelets? That's right, it's B white blood cells.

And let's do another quick check.

True or false, this one.

White blood cells contain haemoglobin, true or false? That's right, it's false.

So haemoglobin is carried in the red blood cells where it's called oxy-hemoglobin and therefore it is the red blood cells that carry haemoglobin, not the white blood cells.

Okay, let's come on to the second practise task of this lesson.

So Ahmed is a rugby player and I want you to describe the purpose of each of the four constituents of blood and explain why they are essential to him during a rugby match.

So we're thinking about red blood cells, white blood cells, platelets and plasma, and what role those four different constituents of blood play in a rugby game? Pause the video now and come back to me when you've completed this task.

Okay, let's compare what you came up with and here's an example.

So the red blood cells contain haemoglobin which carries oxygen and Ahmed needs really good oxygen supplied to his muscles so that he can keep running for that whole 80 minute rugby match.

Meanwhile, we've got white blood cells and they are essential for the immune response.

If Ahmed got injured, they would fight infection and also help with recovery after a hard game due to all those micro muscle tears.

So white blood cells are working really hard during the game, but even more so afterwards in recovery.

And then we've got platelets as we said, they clot the blood so if Ahmed grazed his knee, perhaps he was tackled hard on some rough ground and grazed his knee so it started to bleed.

These would help plug the hole to prevent further blood loss and enable Ahmed to continue to play.

And then plasma as we've just covered off, ensures the blood flow and helps maintain Ahmeds body temperature during the whole 80 minute match and it does that via allowing sweating to happen.

I hope that's what you came up with or words to that effect.

Let's just do a quick summary of this lesson.

So we've covered off blood vessels and blood cells as the two main parts to this lesson and we said there's three different types of blood vessel.

Firstly we've got arteries, so they carry blood away from the heart.

Capillaries and they enable that gaseous exchange of oxygen, carbon dioxide and nutrients in and out of the bloodstream.

And that happens largely at the lungs but also at the muscle site and incidentally in the digestive system as well.

But again, you might cover that off in science but we don't cover it in GCSCPE.

And then the veins which carry blood back to the heart at a lower pressure and because it's a lower pressure they've got those pocket valves within them.

And then we've got four different constituents or parts to the blood.

Firstly red blood cells, so they carry oxygen in a a compound known as haemoglobin.

Secondly, we've got white blood cells and they fight infection.

Thirdly, we've got platelets that clot the blood.

And then lastly, we've got plasma and that makes up the majority of the blood volume.

It's been great to see you again today.

Thanks very much and I hope you enjoyed the lesson.

See you next time.