© Boardworks Ltd 2003 KEY STAGE 4 BLOOD. © Boardworks Ltd 2003 A slide contains teacher’s notes wherever this icon is displayed - To access these notes

© Boardworks Ltd 2003

KEY STAGE 4BLOOD


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If blood is separated it no longer looks like the red liquid that we recognise.

The blood sample separates into two parts.

centrifuge

The top half is a straw coloured liquid called Plasma (55%).

The bottom half is a dark collection of Blood cells (45%).

What is blood?


plasma

blood cell

blood cell

blood cell

The plasma actually surrounds the cells and carries them along as it flows through the blood vessels.

This is the first function of plasma.

As blood is 55% plasma and only 45% cells, the cells are actually suspended within the plasma, a little like people would be suspended within a swimming pool.


Blood flows around the body, transporting substances from one place to another.

it usually picks a substance up from an

exchange site

takes it to a place where it is used

a reaction occurs

Reaction

a useful product and a waste product is made


The blood then transports one or both of these substances to another place in the body.

useful/waste product

cellblood vessel

The cycle then starts again.


blood flowing along a capillary

CO2

CO2

CO2

CO2

CO2

Magnifyplasma

blood cellblood cell

Blood has to rely on its plasma to actually carry some of these useful/waste products.

For example, plasma carries CO2 from the cells to the lungs.


The third and fourth roles are also centred around the moving of a substance from one place to another.

PlasmaPlasma is responsible for carrying dissolved food.

3rd Role:

Remember! Our digestive system breaks down the food we eat to release the useful nutrients.


MouthMouth

AnusAnus

food is eaten

waste is excreted

Useful products of digestion are absorbedabsorbed from the digestive system and enter the blood.

Sugars

Amino Acids

Glycerol

Fatty Acids


The soluble food dissolves into the plasma and is carried from the small intestine to the cells of the body. Here they diffuse into the cells and are used in various chemical reactions.

Sugars Fatty acids

Glycerol

Amino acids

Body cell

plasma


The final role of the plasma is to carry a waste product from the liver to the kidneys.

The waste product is called UreaUrea. .

Urea is made in the liver by the breakdown of amino acids.

As urea is toxic, it must be removed from the body as

quickly as possible!

The blood now has to help the body do this.


This is where the plasma takes control.

It carries the urea from the liver to the filtering organs (the kidneys). As the blood passes into the kidney, the urea is removed from the plasma and passes down a tube that takes it to the bladder.

kidney

bloodureaurea

This urea passes to the bladder where it is stored before it is excreted.


The urea will leave the body within the liquid urineurine.

In summary, this tells us that plasma has a principle role in transporting substances around the body.

Substance Moving from Going to

CO2Cells Lungs

Cells All over The Body

Dissolvedfood

Smallintestine

Cells

Urea Liver Kidney


We’ve come a long way from calling blood just a red liquid. After all, all this is being carried in just the bloods plasma.

Urea

CO2

CO2

Fatty Acids

Amino AcidsUrea

Red Blood Cell

Carbon Dioxide

Sugar

White Blood Cell

Platelets


Blood cells

There are 3 types of blood cell within human blood.

They have different shapes and carry out different functions.

Red Blood Cells

White Blood Cells

(These are actually fragments of cells so we

can’t really call them cells)

Platelets


Red blood cells

Of all the cells these are the most numerous.

In fact, every cubic centimetre of blood contains…

1 cm

1 cm

1 cm5 000,000,000 cells


Therefore, it is not hard to realise that each red blood cell is extremely small.

In fact, each one is only on average 7 micrometers in diameter (one micrometer is a millionth of a metre).

This is a basic diagram of a red blood cell.


Actually, although the red blood cell is a “cell”, it does not contain one of the 3 parts of a “normal” cell.

Red blood cells have no nucleus.

This may seem odd but, there is a reason for it.

Red blood cells also contain a unique substance called Haemoglobin.Haemoglobin.

This is a special iron based pigment whose presence is essential if the red blood cell is to perform its job.

And by the way, its job couldn’t be more important!


Red blood cells carry OXYGEN (OOXYGEN (O22).).

Let’s look at how it performs this job.

The story begins in the lungslungs because this is where the oxygen gas enters the bloodstream.

Remember, during the process of breathing, oxygen gas enters the body and is exchanged for carbon dioxide gas.

The oxygen gas will be needed for the process of respiration.


O2

O2O2

O2oxygen is inhaled

It passes through the breathing system and reaches an alveolus.

The oxygen gas diffuses across the lining of the alveolus and the capillary.

alveolus

O2

O2

O2


Here is a close up showing the diffusion of oxygen gas.

lining of alveolus

moist layer

red blood cell

OO22 OO22

lining of capillary

As the oxygen gas diffuses across the lining of the alveolus, it dissolves in the moist layer.

This speeds up the diffusion process.


If we now concentrate on one red blood cell, we can see how important the haemoglobin molecule is to the process of transporting oxygen.

O2

The oxygen molecule diffuses into the red blood cell.

Haemoglobin + O2

each red blood cell contains the pigment...

These two molecules bind together to produce this new substance.

Oxyhaemoglobin


Oxygen + Haemoglobin Oxyhaemoglobin

It is important to remember that this reaction is happening in red blood cells at the alveolus.

This is how the red blood cells are able to bind hold of the oxygen and carry it within the blood.

Each red blood cell is now loaded with oxygen molecules.

OxyhaemoglobinOxyhaemoglobin




Once these redred blood cells reach the cells of the body, they are travelling through tiny capillaries similar to those found in the alveolus.

cells

capillary

It is here that they offload their oxygen.

In order for this to happen, the Oxyhaemoglobin molecule must be broken down.



The Oxyhaemoglobin breaks down to release the oxygen molecule.

It diffuses across the cell membrane and the lining of the capillary and into

the cell.

In the cell, the oxygen is used in the process of respiration

which produces….

ENERGY


Why are red blood cells shaped like this?

Questions

Well, they are perfectly suited to do their job.

They are specialised in the following ways -

1 There are vast numbers of them.

The more cells there are, the more O2 can be carried and delivered to the cells.


2 They have no nucleus.

This means they have more room for haemoglobin molecules and therefore each red blood cell can carry more oxygen gas.

3 They have a large surface area compared to their volume.

large surface area

small volume


Through having a small volume compared to its surface area, the red blood cell is able to keep the oxygen close to its surface.

This means it can quickly release its oxygen by reducing the time it takes for the gas to diffuse out of the cell.

O2

The distance for the gas to move is much smaller in a cell shaped like this.

O2

alternative cell design

The overall effect of this means that the blood can cope with the oxygen demands of the body.


4 The diameter of red blood cells is slightly larger than the average diameter of a capillary.

red blood cellcapillary

This means that the red blood cell is forced to slow down as it passes through the capillary.

This means the exchange of the gas will definitely happen.

It also means the surface of the red blood cell will be exposed to the surface of the capillary.


Let’s now consider the white blood cell.

The white blood cell is bigger than the red blood cell.

It has a much more varied shape and there are differentdifferent types of white blood cell within the blood.

White blood cells play a part in the defence system of the body.

They are designed to fight microbes such as bacteria and viruses.


There are far fewer white blood cells within the blood compared with red blood cells.

When the body fightsfights disease, more white blood cells are produced. With some diseases, doctors can establish how healthy someone is by testing their blood to see how many white blood cells they have.

TestPerson is Normal

white blood cell number is low

white blood cell number is higher

Disease

Test Person is suffering

from disease


Our final cell is the platelet.

As we mentioned, the platelet is actually a fragment of a cell.

Therefore it does not have a nucleus.

They are also much smaller than both the white and red blood cells.

Their role is to help to clot the blood when the body has a wound.

skin

Blood capillary






ActivityActivity






Multiple choice questions


Which of these is not a function of blood?

A To support the body.

B To fight disease.

C To carry gases around the body.

D To carry hormones to their site of action.


What is the name of the pigment within red blood cells?

A haemoglycin

B haemoglobin

C haemoglycerol

D haemoglucose


Which of these descriptions best suits the shape of a red blood cell?

A a doughnut

B a round flat plate

C a biconcave disc

D a disc shaped shell


What is missing from a red blood cell?

A the nucleus

B the cytoplasm

C the cell membrane

D answers A and B


What is the name of the straw-coloured liquid in which blood cells are suspended?

A haem liquid

B cytoplasma

C blood fluid

D plasma


What percentage of blood is made up of plasma?

A 20%

B 40%

C 55%

D 65%


Which of the these substances are carried by blood plasma?

A oxygen, glucose, urea and amino acids

B amino acids, carbon dioxide, oxygen and fatty acids

C fatty acids, glucose, oxygen, glycerol

D urea, fatty acids, amino acids and carbon dioxide


Blood plasma...

A defends the body against invading microbes.

B helps the blood to clot.

C transports urea from the liver to the kidneys.

D binds to oxygen.


Red blood cells...

A need oxygen.

B attract carbon dioxide.

C carry oxygen.

D repel carbon dioxide.


The white blood cells are larger than red blood cells. Their job is to...

A make the blood clot.

B carry oxygen to the cells of the body.

C defend the body against invading microbes.

D carry carbon dioxide.

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© Boardworks Ltd 2003 KEY STAGE 4 BLOOD. © Boardworks Ltd 2003 A slide contains teacher’s notes wherever this icon is displayed - To access these notes