Blood

A heart isn’t much good without lots and lots of blood!

But what actually is blood? Let’s find out…

Plasma

This is the sloshy part of your blood. An adult human has the same amount of liquid in their blood as three big bottles of cola!

Plasma is actually pale yellow in colour, it only looks red because of the red blood cells.

Red blood cells

If you look at red blood cells under a microscope, they look like squashed footballs!

These funny looking cells are packed with nutrients and oxygen.

The part of the cells that carries oxygen is called haemoglobin.

The more oxygen it has – the redder it is! That’s why the blood coming from your lungs is brighter than the blood going in.

Did you know?

There are about 25 trillion red blood cells in your body!

White blood cells

White blood cells are one of the main parts of the body’s immune system.

They defend against certain bacteria, viruses and lots of infectious diseases.

Platelets

Platelets are tiny odd fragments of cells that help your blood to clot or stick together when you cut yourself, forming a scab.

If you’ve covered a balloon with scraps of papier mache, it’s a bit like that – lots of small bits sticking together to make a very strong surface.

Platelets and blood cells are made inside your bones but the liquid comes from what you’ve eaten and drunk. That’s why it’s a good idea to drink plenty of water.

Blood transfusions

Because blood is so precious, if someone is very poorly or injured they might not have enough of their own to go around.

Blood transfusions are a way for blood to be shared.

Healthy grown ups can give some of their blood to be kept for people who need a top up.

There are eight different types of blood, A, B, AB and O – all of which can be positive or negative. O negative is the most common and B plus is the most rare.

Does it matter which blood type I am?

You wouldn’t be able to tell the difference by looking and normally it doesn’t matter which you are.

It does matter though if you were to donate or receive donated blood.

Doctors will check the blood carefully to make sure you get the exact type you need.

They’ll be finding out all about the cool stuff that goes on inside your heart and how it manages to pump blood around your body all the time – even when you’re asleep!