Lesson video

This lesson is called The human circulatory system and is from the unit Transport and exchange surfaces in humans.

Hi there, my name's Mrs. McCready, and I'm here to guide you through today's lesson.

So thank you very much for joining me.

In our lesson today, we're going to explain the role of the circulatory system in supplying every living cell in the human body with the substances it needs to stay alive.

Now we're going to come across a number of keywords in our lesson today and they're presented on the screen now for you.

You may wish to pause the video to make a note of them, but I will introduce them to you as we come across them.

Now in our lesson today, we're going to first of all look at nutrients and waste before we then go and have a look at the role of the circulatory system.

So I hope you're ready to go.

I certainly am.

Let's get started.

So the human body is made up of billions of living cells, absolutely billions of them.

And therefore we are an example of a multicellular organism, where multi means many and cellular means of cells.

So we are made up of many, many cells, billions in fact.

Now, every living cell within our body requires nutrients in order to function.

So for instance, carbohydrates are a chemical store of energy and are required for cellular respiration.

Amino acids are used to make proteins such as haemoglobin.

And minerals provide ions which are important for many cellular processes.

For instance, Fe2+, so an iron ion, is used in haemoglobin to bind oxygen.

And all of these nutrients in their various forms that they're turned into within the cell enable the organism to live, grow, and repair itself.

Now, oxygen and nutrients must be absorbed.

So the lungs absorb oxygen and the digestive system absorbs many nutrients, including carbohydrates and proteins.

Now, oxygen and the nutrients absorbed through the digestive system must be moved around the body to where they are required.

And this movement happens via the circulatory system, where oxygen is moved from the lungs to the cells that require it.

And nutrients are moved from the digestive system to the cells that need it.

In other words, all of the living cells within our body.

Now, all of these living cells generate waste products as well.

For instance, cellular respiration produces waste carbon dioxide and water, and proteins are broken down into nitrogenous compounds.

Now, waste products must be collected and removed from the cells that have made them.

So the lungs excrete carbon dioxide, we breathe out carbon dioxide.

The colon removes waste products, including water and cell parts, which are defecated.

So we poo them out when we go to the toilet.

And the kidneys remove waste products, including water and nitrogenous compounds.

And these are excreted via urination.

So we wee them out when we go to the toilet.

Now all of these waste products also need to be moved around the body from the cells which make them to the lungs or the colon or the kidneys, which enables them to be excreted out of the body.

And moving them around the body is a function that is provided by the circulatory system.

So let's just check our understanding.

So these three students are discussing how nutrients and waste are absorbed, excreted, or transported.

But who is correct? So Andeep says, "Some nutrients, like carbohydrates, are absorbed through the digestive system." Jacob says, "The lungs excrete carbon dioxide and oxygen." And Sofia says, "Cell parts and carbon dioxide are excreted through the kidneys." But who is correct? I'll give you five seconds to decide.

Okay, so hopefully you've come to your decision and you've said that Andeep is correct, because nutrients like carbohydrates are absorbed through the digestive system.

But Jacob is incorrect in saying that lungs excrete oxygen.

That's wrong.

And Sofia is incorrect when she says that cell parts and carbon dioxide are excreted through the kidneys.

So well done.

So what I'd like you to do now is to use the diagram of the human body and firstly add labels with arrows pointing to the parts of the body where breathing, digestion, defecation, and circulation occur.

Then I would like you to add some short descriptions next to each label to state which materials are being absorbed or excreted via those points of the body.

Then I would like you to explain what would happen to these processes if you lost a lot of blood due to an injury.

So pause the video and come back to me when you are ready.

Okay, let's just check our work then.

So I asked you firstly to add labels with arrows pointing to the parts of the body where breathing, digestion, defecation, and circulation occur.

So you should have added a label to somewhere around where the lungs are for breathing, around the small intestines perhaps for digestion, a bit lower down around the colon and the large intestine for defecation, and in the centre of the chest where the heart is for circulation.

Then I asked you to add short descriptions next to each of those labels to state which materials are being absorbed or excreted via those processes.

So against breathing, you should have said that oxygen is being absorbed and carbon dioxide is being excreted.

Against digestion, you should have said that nutrients such as carbohydrates and proteins are being absorbed.

And against defecation, you should have said that waste such as water and cell parts are being excreted.

So just check your work.

Then I wanted you to explain what would happen to these processes if you lost a lot of blood due to an injury.

So you could have included in your answer that blood transports nutrients to all living cells in the body and it also transports waste products from all living cells to excretory systems and the lungs.

Now if a lot of blood was lost, these essential processes would not be carried out and therefore cells would not be able to absorb the necessary nutrients to live, grow, and repair themselves, and neither would they be able to excrete waste products.

Now you might also have added this final idea that eventually the cells would die and therefore the individual would die too if this was left untreated.

So review your answer to that.

That was quite a complex process of bringing all those ideas together.

So well done indeed.

Okay, so let's look at the next section of our lesson, which is on the circulatory system itself.

So the circulatory system includes the blood, which is what is transporting all of these nutrients and waste products.

Now, the blood flows through blood vessels which go throughout the whole body.

And the heart is also part of the circulatory system because it is the heart which pumps the blood around the body through the blood vessels.

So let's look at these in a bit more detail.

Blood contains red blood cells, which carry oxygen, white blood cells, which are involved in fighting disease, platelets, which are tiny little bits of cells and they plug holes in the vessel walls and encourage blood to clot and scabs to form.

And they prevent us from just bleeding and bleeding and bleeding.

And then the plasma, which is a fluid which all of these cells are suspended within and all of the nutrients and the waste products are either dissolved or suspended in, and that allows the blood to flow around the body, carrying all of these cells and nutrients and waste products.

So the blood vessels are the tubes through which the blood is flowing.

Now, arteries take blood away from the heart and these are really muscular vessels, which can contract and give us our pulse.

Have you ever tried checking your pulse either on your wrist or maybe up in your neck? Well, what you are doing is feeling the artery and the wall of the artery contracting as it beats, as it pumps blood around our body.

There are also veins in our body, which return blood back to the heart.

And then there are very, very fine, narrow capillaries, which is where the nutrients and the waste are interchanged with tissue.

So when nutrients leave the blood and where waste products enter the blood and are therefore able to be moved around the body.

And then finally, the heart.

So the heart is a pump and it takes in blood and pumps it back out again and moves it through the blood vessels, the arteries, and the veins and the capillaries around the body.

And it is regularly contracting and relaxing to push blood through the circulatory system.

So let's just quickly check our understanding.

Which of the following are blood vessels in the circulatory system? Arteries, platelets, capillaries, and plasma.

Which do you think? I'll give you five seconds to decide.

So hopefully you've spotted that arteries and capillaries are the blood vessels in this list, and the platelets and the plasma are part of the blood itself.

Well done.

So what I'd like you to do now is using the words below, write a detailed description of the circulatory system and its components.

So the words include circulatory system, blood and its components, blood vessels and the types of vessels that we've looked at, and the heart itself.

So pause the video, take your time to write a really detailed description covering all of those points and come back to me when you are ready.

Okay, let's see what you might have written then.

So you should have included that the circulatory system includes blood, blood vessels, and the heart, and that blood contains red blood cells.

And you might have added that they carry oxygen.

White blood cells, you might have added that they fight disease.

Platelets, which you might have added clot blood and form scabs.

And plasma, and you might have added that that is the liquid that everything is dissolved in or suspended in.

Then you should have included that blood flows through blood vessels, including the arteries.

And you might have said that these are the vessels which take blood away from the heart.

Veins, which return blood back to the heart.

And capillaries, which allow nutrients and waste products to move between the blood and the cells that they are supporting.

And finally, you should have added that the blood is pumped around the body by the heart and through the blood vessels.

So again, check your work over, make sure you've got all the really important points there, add in anything that you need to, and well done for putting in such a concerted effort there.

Okay, so in our lesson today then we have seen that humans are multicellular organisms, and every cell within our body requires nutrients for energy, growth, and repair, and produce waste products that must be excreted.

And it is this circulatory system which is transporting substances between the cells and the lungs, the digestive system, and the excretory systems. And the circulatory system consists of blood, blood vessels, and the heart in order to do that transportation role.

So thank you very much for joining me today.

I hope you enjoyed that lesson and learned a lot and I hope to see you again soon.

Bye.