Blood is made of two different things called cells and plasma. The plasma is like water, and that’s where it comes from. When you drink the water goes into your tummy and through your gut. There are blood vessels (the tubes that blood runs in) very close and touching your gut, and the water gets pulled out into the blood. It’s a bit like a sponge – a dry sponge will soak up water that is touching it.
Other things like sugar get pulled out as well, this is how blood takes food around your body everywhere that needs it. It carries lots of other things as well, including getting rid of things that your fingers and toes have used up when they are working hard. It goes through something called your kidneys, which are a filter or very, very fine net. They catch all the rubbish your body has made so you can get rid of it and squeeze out some of the water. This is where your urine or wee comes from – it is your body’s way of getting rid of the rubbish.
The other part of blood is the cells. These are little bits of you that float around in the plasma and there are three types – red blood cells, white blood cells and platelets.
Red blood cells – are called that because they’re red! There are lots of them, that’s why your blood looks red, and they carry oxygen, the air you breathe. They are shaped like little doughnuts so they can squeeze through to all parts of your body. They are made in something called marrow.
All your big bones aren’t solid – you would be too heavy to move! Inside them is a special sort of fat called marrow. This marrow grows baby red blood cells, then they go round and round your body for about 3 months until they are too old.
White blood cells – That big white lump is a white blood cell. There are a few different types of white blood cells, they are made by marrow in the bones as well. They help stop you getting sick by finding germs and eating them. When you cut yourself a lot of white blood cells go there to stop germs getting into you through the cut. If you’ve ever had an infection or pimple you have seen pus. This doesn’t look very nice, but it is a sign that your body is working hard to get rid of the germs. It is made from dead bits of skin, white blood cells and germs, and shows that lots of white blood cells have rushed there to get the germs out of your body.
Platelets – These are tiny, tiny little cells, smaller than red and white blood cells. They are made in the marrow too, and they make scabs.
This shows lots of platelets around a red blood cell, you can see that they have lots of arms like an octopus. When you have a cut the platelets get all tangled and stick together, when they dry out they have made a scab. This protects you and lets the skin grow back underneath.
So you can see that blood works very hard. You need the water part, plasma, to carry all the food out and rubbish back, and the red blood cells, white blood cells and platelets are made inside your bones and carry air all over your body, stop germs and make scabs.
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