ABO Blood Types Demonstration
Demonstrator notes
Today we will be learning about blood typing. As you know, we all have blood flowing through our
veins and arteries. This blood is what transports nutrients and oxygen to our cells and transports
some waste products out of our body. The average adult has about 5 litres of blood flowing through
its veins – that’s five milk cartons worth!
I’m sure everyone here can think of a time when they have hurt themselves and there was a lot of
blood – right? Well sometimes people can be so sick or hurt that they lose enough of their 5 litres
that their body has trouble working properly and their life is at risk. This is when we need to give
them what is called a blood transfusion. A blood transfusion is where a healthy donor donates some
of their 5 litres of blood (less than half a litre, about the size of a chocolate milk container... it can
easily be spared with no harm to the donor). This blood is put in a bag, processed and then given to
the person who needs more blood. This donation can be the difference between someone getting
very sick and dying, and a full recovery, so it is very important.
But there are some biological rules as to whose blood the sick person’s body can accept. Just like
each of us is different, there are different types of blood too! So I am here to explain one type of
blood typing called the ABO system. This is the most important blood typing system, but there are
others which you might learn about later.
Firstly, what is blood!?
Blood is made up of many different parts. All these bits are flowing around in your body all mixed up.
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White blood cells work as part of your immune system, protecting you from infection;
Platelets help your blood to clot when you have injured yourself (think of scabs!)
Red blood cells carry oxygen around the body and have things called antigens on their
surface. Antigens act as a kind of identification for the red blood cell, so other cells know it
belongs in the blood system
Plasma is the clear watery substance in blood. Sometimes you see plasma when you graze
your knee. Plasma is the main way we transport things around the body, but today we are
interested in the antibodies it transports. Antibodies circulate through the plasma in the
blood system, checking cells antigens for identification. If an antibody checks a cells antigens
and finds it doesn’t belong, it locks onto it and marks it to be destroyed by the immune
system.
The ABO blood typing system has four types: A, B, AB and O.
(Draw on board, T’s are antigens, diamonds are antibodies)
A
A Antigens on red cell surface,
anti-B Antibodies in plasma
B
B antigens on red cell
surface, anti-A antibodies in
plasma
AB
Both A and B antigens on red
cell surface, no antibodies in
plasma
O
No antigens on red cell
surface, both anti-A and antiB antibodies in plasma
Does anyone know what blood type they are? Yes? I am blood type A so my blood has A antigens on
its red blood cells, and anti-B antibodies, like this.
So which blood types can donate to other blood types? I have this model here to help demonstrate.
(Get model)
I want you to imagine these white tubes are recipients (i.e. the sick person who needs blood) with
different blood types. Can I have a volunteer come up here?
Volunteer, please run your finger down the A type blood vessel – what do you feel? Scratchy or soft?
And the B type? Scratchy
Okay, what you are feeling are the antibodies. Anti-A are scratchy, anti-B are soft.
Run your finger down the AB vessel – smooth? No antibodies, just like in the diagram. And the O?
Both scratchy AND soft, because O type has both anti-A and anti-B right?
So now we need to look at the donor blood. These balls are going to be our red blood cells, and look,
they have antigens on the surface.
Anti- A: scratchy white
Anti-B: soft white
Antigen A: soft black
Antigen B: scratchy black
Now let’s see what happens when we put a A type donor cell down the A type recipient vessel.
It rolls down with no problems!
What about if we put an A type donor cell down the B type recipient vessel. Uh-oh! We’ve gotten
stuck! Now this is showing that the anti-A antibodies are sticking to the A antigens, holding onto it
until the immune system destroys it.
This sticking together is called ‘coagulation’ it’s the same thing that happens when you get a scab,
but you definitely don’t want a scab INSIDE your blood vessels do you? It will block them and no
more blood can get through – and then you will be in trouble! Coagulation is a bad thing we are
trying to avoid by matching the blood types properly, otherwise we make the sick recipient even
sicker!
So let’s keep experimenting and see if we can fill out this table you have in front of you.
Worksheet – ABO blood typing
Complete the following table:
Donor type
Recipient type
A
A Antigens on
red cell surface
Scratchy, black
A
Anti-B
antibodies in
plasma
Scratchy, white
B
Anti-A
antibodies in
plasma
Soft, white
AB
No antibodies in
plasma
Smooth
O
Anti-A and antiB antibodies in
plasma
Scratchy and
soft, white
B
B antigens on
red cell surface
Soft, black
AB
A and B antigens
on red cell
surface
Scratchy and
soft, black
O
No antigens on
red cell surface
Smooth

X
Complete this diagram, showing which donor blood types can donate to which recipient types.
Donor
Recipient
A
A
B
B
AB
AB
O
O
Now you should have something that looks like this:
Donor
Recipient
A
A
B
B
AB
AB
O
O
Can anyone notice anything about AB blood type? That’s right; AB recipients can accept any donor
blood. AB is called the ‘Universal recipient’
Can anyone notice anything special about O blood type from this diagram? Yes, O is called the
‘Universal donor’ meaning it can donate to any of the four blood types. Having this type of blood on
hand at hospitals is very important in an emergency because it saves the time it usually takes to
figure out what blood types someone is, because doctors know they know they can safely give O
type blood to anyone.
However, we can’t rely on people with 0 type blood to do all the donating; we all need to donate to
make sure we have all the different types of blood on hand! Donated blood isn’t just used in
emergencies when people are bleeding, but is used when babies are born, for both the baby and the
mother. It is also used for cancer patients whose blood is no longer working for them. According to
the Australian Red Cross Blood Service, one donation of 470ml blood (remember, the small
chocolate milk container?) can save THREE people’s lives! And the leftover bits are used to make
other life-saving products such as vaccinations.
You need to be 16 years old to donate blood and meet a few other easy-to-meet requirements, but
your donation can mean the world to someone else and their family. It can save their life!