Blood cells all follow a set pattern of development. They form in the bone marrow (the spongy part inside some of the bones) and then pass into the blood.

There are three types of blood cell:

Red blood cells which contain haemoglobin to carry oxygen around the body

Platelets which help to prevent and stop bleeding

White blood cells which fight infections.
There are two main types of white cell: neutrophils and lymphocytes, which work together to fight infection in the body.