Lesson video

Hi everyone and welcome to this lesson from the Oak National Academy.

Today's lesson is all about adaptations of the human lungs for gas exchange.

What that means is it's all about the features that the lungs have that make them good at their job.

I'm Mrs. Wee, and by the end of today's session, you'll be able to describe how the human lungs are adapted to increase the amount of gas exchange they can do.

Let's look at our keywords.

So we have alveoli, capillary, diffusion, surface area.

I'm gonna show you our definitions for our keywords.

There's no need to try and memorise these now.

I'll explain what each of the mean as we go through the lesson.

But if you like, you can pause the video here, read through them, or even copy them down so you can refer back to them later.

Here they are.

Today's lesson is in two parts.

First of all, we'll talk about the structure and function of an alveolus.

Then once we've done that, we'll move on to the adaptations of an alveolus.

But first, let's talk about what an alveolus actually is.

So far in this unit, we have learned about the process of gas exchange and about the structure and the function of the gas exchange system.

Now we're gonna look at how the lungs are adapted to carry out as much gas exchange as possible, and we're going to be mainly focusing on this tissue in the lungs called alveoli.

Let's do a recap of the lungs to make sure we're ready for the next step.

The lungs are involved with breathing and they carry out gas exchange.

They are made up of many different parts.

Let's look at those parts.

We have bronchi.

So air enters our lungs through one of two tubes called bronchi.

These bronchi branch off into even smaller tubes called bronchioles.

At the end of each of these bronchioles, these smaller tubes are structures called alveoli.

A quick language in grammar lesson here.

The word alveoli is the plural form of the word alveolus.

The words come from Latin.

So when you're pluralising them, it's a bit more complicated than putting an E or an ES on the end of them like we do in English.

So to sum up, alveolus is singular.

We use this word when we're talking about one of these structures.

The word alveoli is plural.

We use this word when we're talking about more than one of these structures.

So what is an alveolus or alveoli? These are tiny air sacs in the lungs.

There are millions and millions of them, and they're the focus of today's lesson.

Let's see if you understood that.

The diagram shows the human gas exchange system, which letter shows the alveoli.

So you can pause the video here or just wait for five seconds, think about your answer, and then click play when you're ready to find out what the answer is.

It's B.

B shows the alveoli.

So E is the trachea or sometimes called the windpipe.

Air flows through that going into the C, the bronchi, then air flows into the A, the bronchioles.

And in a previous lesson we talked about D, the diaphragm and how that helps us to breathe.

But today's lesson all focusing on B, the alveoli.

Alveoli are tiny air sacks in the lungs that carry out gas exchange.

They're an important tissue of the lungs.

So let's remember those organisational words that we kinda learned in year seven.

So we have cells, small swimming thing, lots of cells build together to make tissues like alveoli or like muscle tissue.

Tissues build together to make organs like the stomach, the brain, the skin.

Organs build together to make organ systems like the gas exchange system.

And lots of organ systems can make a complicated organism like human beings or cats or dogs or trees or fungi.

So yes, so that's what I mean by tissue.

That's where that word is kind of in our level of structure of living things.

So alveoli are made up of lots of cells that makes them a tissue.

Let's zoom in on some alveoli and see them in a bit more detail.

So here we have dozens of alveoli bunched together in a clump.

I always used to think that they look like a bunch of grapes, but one of my students told me she thought they looked more like a raspberry.

And I agree with her.

So here are alveoli, these are a few dozen of them.

And alveoli are surrounded by these tiny blood vessels known as capillaries.

So capillary singular, capillaries plural.

Let's look at an individual alveolus.

Remember that word is for just one of them.

Here we go.

So look at my little purple circle that's circling around one of these little tiny structures, and we've now got it in much more detail on the right hand side here.

So this is an alveolus and this is where gas exchange takes place.

We covered gas exchange in a previous lesson, but just a quick reminder, during gas exchange we have oxygen diffusing out of the alveolus into the capillary, and then we have carbon dioxide diffusing out of the capillary into the alveolus.

So it is exchanging those gases, the gases being auctioned, carbon dioxide, they're moving from the capillary to the alveolus or back again.

How are you doing so far? Let's find out and check.

True or false, alveoli are important cells in the lungs.

Is that true? Is that false? Pause and think about that.

It's false.

Justify that answer.

So maybe you didn't get it right, that's fine.

There's still a chance to have a go at a question about this.

So is that false because the alveoli are an organ because they're made up of cells? Or is it false because the alveolar are a tissue because they're made up of cells? Pause and think about that now again.

They are a tissue, so B is the correct answer.

Cells build up to make tissues.

Tissues build up to make organs, organs build up to make organ systems. Well done if you've got that right.

So it's our first practise task of the lesson.

Let's have a go at this together.

So number one, label the structures in the diagram using some of the keywords in the list.

So you won't necessarily have to use all of them, maybe just some of them.

Alveolus, bronchus, so that's the singular of bronchi, capillary oxygen molecule, carbon dioxide molecule, and trachea.

So labelling that diagram with some of those keywords, maybe all of them, maybe some of them.

Number two, add arrows to the diagram to show the direction of movement of oxygen molecules and carbon dioxide molecules during gas exchange.

And then three, I want a written description of what is happening in the diagram.

So pause the video here for a few minutes, whilst you attempt those questions, good luck.

Okay, how did you do? Let's look at some of your answers.

So label the structures in the diagram using some of the keywords on the list.

So we have the alveolus, we've got the capillary, the blood vessel right next to the alveolus, we've got oxygen molecules, which I've put in red here.

Carbon dioxide molecules, which I put in blue here.

So there's more oxygen as kind of percentage inside our alveoli, inside our blood.

And so that's why there's, the color's not super important, but the fact that there's more oxygen molecules than there are carbon dioxide molecules.

That's why it's labelled that way around.

So next thing need to do was to add arrows to the diagram to show the direction of the movement of oxygen molecules and carbon dioxide molecules during gas exchange.

So this is that overall movement.

Molecules are kind of moving all around in carbon dioxide during diffusion.

And so this is what is the overall movement of those molecules? So I've done a big red arrow to show oxygen moving.

So oxygen generally is moving from an alveolus to the capillary.

Carbon dioxide, my big blue arrows are moving the other way around from the capillary back into the alveolus.

Well I dunno if you got that right.

Last question.

Describe what the diagram is showing.

There's lots of different ways you could describe this.

Here's one model answer for what you could have written.

The diagram shows a part of the lungs called an alveolus.

The alveolus is next to a capillary and is carrying out gas exchange.

This is when oxygen molecules diffuse from the alveolus into capillary and at the same time, oxygen dioxide, at the same time carbon dioxide there we go, is diffusing from the capillary into the alveolus.

So well done if you got that right as well, great job.

That was our first practise task.

Wow, that went fast.

Okay, we've already learned everything we need to know about the structure and function of an alveolus.

Now we're looking at the adaptations of an alveolus.

Let's look at that word adaptations in a bit more detail.

'Cause maybe you're not super familiar with it.

That's totally fine.

So adaptations are special features, living things, living organisms have that helps them survive and perform their function.

So I've got some pictures of some living organisms here.

I've got a hair, I've got some cacti and I've got some fungi.

Can you pause the video now and have a think how might these things be adapted to perform that function or to survive? How did you guys do? I'm sure you came up with so many interesting adaptations.

So I'm just gonna give one for each, but there's tonnes and tonnes and tonnes you could have said.

So for the hair, what I thought of is prey animals.

So prey, P-R-E-Y, not like pray, P-R-A-Y, prey animals, animals that are eaten by other animals like hares, they have their eyes on the side of their head and that gives them a really, really good view.

So being you're having your eyes here means like, oh, okay, you are easier.

It's easier to see predators that are coming for you.

So that's one way that prey animals like the hare are adapted.

The cacti, tonnes of things you could said about cacti.

A thing I thought of was they've got spines on the cacti instead of leaves, and that reduces water evaporation from the plant, which is so useful 'cause cacti are desert plants.

So you know, they need to conserve water wherever possible.

And then for the fungi what I thought is that you might already know some fungi are delicious, like mushrooms. I've got no time for hate if you hate mushrooms, mushrooms are delicious.

But some of them are really poisonous and they make these toxins so that animals don't eat them.

So that's one way that some fungi are adapted for their function and it helps them survive.

So did that all make sense to you? Let's check.

Complete the sentences about adaptations.

So read through the sentence and think about what words might go in those gaps.

Pause the video here.

What do you think about that? Okay, let's look at the answers.

Adaptations are special features, living things have to help them survive and perform their function.

Great work everyone.

So what has that all got to do with the lungs and the alveoli? So it's not just multicellular organisms like hares and plants and fungi that have adaptations.

Pretty much all living tissue, all living things have adaptations so that they can perform their function really, really well.

So alveoli also have adaptations.

We're gonna look at some of those now so we can learn about how that relates to gas exchange.

So the lungs have many alveoli and this increases their surface area.

That's really important because that means there's more space, there's more opportunities for those oxygen and carbon dioxide molecules to diffuse in and out of the alveolus.

And that means that more gas exchange can occur.

That can be quite a tricky concept to get your head round.

So we're gonna look at two items that will help us understand this surface area concept.

So surface area is the total area of all of the faces of an object.

Here we've got a sponge and we've got this cloth, which is kind of in the shape of a bag or a mitten.

Which do you think will absorb more water? And can you tell me why? So it's a sponge gonna absorb more water.

Is the cloth gonna absorb more water? Take five seconds now and pause the video to think about your answer.

It is the sponge and you probably figured that out, but can you tell me why? It's because water can only be absorbed through the surface of an object.

And because of the shape of the sponge with all of the holes inside it, it just has far more surface.

It has a much larger surface area.

So how does this relate to lungs? So if the lungs were just an empty bag like this cloth, they wouldn't be able to carry out nearly as much gas exchange.

The lungs are more like a pair of sponges.

They're filled with millions of alveoli, these tiny little air sacks, these tiny little sponge holes which can each carry out gas exchange.

So overall the surface area of the lungs is greatly increased.

Right, let's check to see if that all made sense to you.

Which structure would carry out more gas exchange? So we've got two structures here.

We've got this A, and we've got this structure here, B.

So A here is what I've drawn.

This is what the bronchioles would look like if there was no alveoli at the end of them.

And B is more representation of what the bronchioles are really like.

They've got these clusters, these clumps of alveoli at the end of them.

So which structure would carry out more gas exchange? Structure A would be better, structure B would be better or they would be equally as good as each other.

Pause the video whilst you think about your answer? It would be B, structure B would be better.

So why would structure B carry out more gas exchange? Is it because it's got a larger surface area? Is it because it's got a bigger volume? Is it because it's more spherical? Pause the video video again.

Think about your answer.

It is A, it's because they have a larger surface area.

Great job if you got that right.

Let's move on to our next adaptation.

Another adaptation of the alveoli is to do with their walls.

The walls of an alveolus are one cell thick.

Lots of people get confused by this phrase.

Remember that the alveoli is a tissue, which means that it's made up of lots of cells.

When I talk about the alveolus walls, I'm not talking about cell walls.

Cell walls are those cellulose cell walls that are inside a plan cell.

Alveoli are tiny air sacs that are filled with gas inside.

So I'm circling the inside.

So here's the inside of an alveolus.

So there's no solid structure inside that.

It's just gas in there.

But the outside edge, so I'm circling now, one of the cells on the outer edge.

So these cells here make up the wall of the outside of the alveolus.

They're each made of a cell.

So the wall, what I'm calling this outer boundary of the alveolus is made up of one layer of cells, one cell thick.

Not cell walls, like in a plant cell.

They're made of whole cells and cells.

Hopefully that's cleared that up.

Let's look at this wall of cells in even more detail.

So we can see, yeah, this layer is made up of one cells and the reason for this, so it provides a short diffusion distance for the oxygen and the carbon dioxide molecules to travel.

So here in red are my oxygen molecules.

Let's have a look.

Yeah, they are crossing that alveolus wall from inside the centre of the alveoli where there's just gas, just air over eventually into a capillary.

Let's look at what would happen if the outer wall of the alveolus was a lot thicker.

So here are my oxygen molecules in red and they're gonna cross over these walls.

So which wall do you think that the oxygen molecules will travel over faster? Will it be the wall that's made of only a single layer of cells? Will it be the wall that's made up of multiple layers of cells? Pause the video here while you think about your answer.

Let's have a look and see.

Well done.

You probably guessed that the molecules cross the one cell thick walls faster than they would if the alveolar walls were thicker.

So these one cell thick walls make sure that there's a short diffusion of distance for the molecules to travel.

This means more gas exchange can occur.

How did you find that? Let's check if you understood.

Complete the sentences about the adaptations of the alveoli.

Use some of the keywords in the list.

Gas exchange, diffusion, atom, carbon dioxide, breathing, cell.

Pause the video whilst you have a go at those sentences.

Let's see how you did.

Alveoli are one cell thick.

This means there is a short diffusion distance for the oxygen and carbon dioxide to travel between the alveolus and capillary.

This means that more gas exchange takes place in the lungs.

Great work everyone.

So our next adaptation is about the capillaries that are near the alveoli.

So alveoli is surrounded by a network of capillaries.

Capillaries are tiny blood vessels that bring oxygenated blood to body cells.

Let's have a look in a bit more detail.

So those are, on the screen right now, a bunch of alveoli.

We've got the capillary, which is in the purple there, which is surrounding all around the outside of the alveoli.

Looking at one alveoli, each alveolus is next to really, really super close to a capillary.

So how is that helpful? What does that do with gas exchange? So capillaries are important because the movement of blood takes oxygen away from the lungs and brings carbon dioxide to the lungs.

We're gonna look at the wall of an alveolus and the capillary closer up.

So we've got the blue dots, which represent carbon dioxide, and we've got the red dots which represent oxygen molecules.

So you can see that the capillary brings carbon dioxide to the alveolus and the oxygen molecules diffuse out of the alveolus into capillary.

The capillary being so close to the alveolus and the fact that there are so many capillaries means that more gas exchange to take place.

So how important are the capillaries? What would happen if they were much further away or if they just weren't surrounding the alveoli? So without capillaries, carbon dioxide would not be brought to the alveoli and be removed from the body.

Oxygen would diffuse out of the alveoli and it would build up.

So there we have oxygen molecules moving out of the alveolus, but they've got nowhere to go.

So eventually there'll be an equal concentration of oxygen inside the alveoli and outside.

And so then there's no concentration gradient.

Okay, so that means there's no diffusion gonna be happening, and so gas exchange is gonna stop.

So the capillaries are super important in maintaining the concentration gradient and ensuring that gas exchange keeps happening.

How much have we learned about the adaptations of an alveolus? Let's check.

Match the adaptation to the reason why it helps gas exchange occur.

So lots of alveoli, match that to one of the reasons on the right hand side.

One cell thick walls, oh my goodness, one cell thick walls, there we go, match that up with one of the reasons.

And good blood supply, that's about the capillaries.

Match up with one of the reasons.

Pause the video once you match those up.

Lots of alveoli are there so that we have a large surface area for our lungs.

The alveoli has one cell thick walls for a short diffusion distance, and so then there's a good blood supply to the alveoli to maintain the concentration gradient.

Well done if you've got all of that.

It's our last practise task of today's lesson.

And now we're gonna look at a gas exchange system in another organism.

So fish use gills to carry out gas exchange rather than having lungs.

The gills are made up of filaments where the gas exchange occurs.

Gills take in dissolved oxygen from the water around the fish and remove carbon monoxide from the fish.

Hopefully you're already starting to see some similarities there between how gills work or well, what gills do and what lungs do.

So the task is fish gills have many adaptations to help gas exchange occur.

We've got many filaments to increase surface area, so they're surrounded by capillaries to maintain a concentration gradient.

The gill filament walls are one cell thick, giving a short defusion distance for molecules to move over.

Describe the similarities and adaptations for gas exchange between fish gills and human lungs.

So look at those bullet points, read through that information, really try and absorb it and understand it.

How is that similar to how the human lungs are adapted for gas exchange.

Pause the video now to give yourself some time to write your answer.

Let's look at a model answer to that question.

There are lots of gill filaments that increases the surface area of the gills.

Similarly, there are many alveoli and that increases the surface area of the lungs.

Both the fish gills and alveoli are surrounded by capillaries which maintains the concentration gradient of gases so diffusion can occur.

Both the gill filament walls and the alveoli walls are one cell thick, giving a short diffusion distance for molecules to diffuse over.

Well done if you spotted all of those similarities.

We have covered a lot today, and hopefully you have a much better understanding of the structure and function of the alveoli and how they're adapted to carry out their function.

That's recap what we've learned, once more to really help us stick in our memories.

The lungs are made up of millions of alveoli, which are adapted to carry out gas exchange.

There are many alveoli in the lungs to increase the surface area.

The walls of the alveoli are one cell thick to create a short diffusion distance for oxygen and carbon dioxide to diffuse.

The alveoli are surrounded by capillaries carrying blood to maintain a concentration gradient of gases between the alveoli and the capillary.

Amazing work today.

You've learned so many new keywords and ideas.

Have a bit of a break now and I'll see you soon for our next lesson.