What is blood?
Source: NHS
Your body carries aroundfourto six litres (7to 10.5 pints) of blood. Blood is made up of red blood cells, white blood cells and platelets in a liquid called plasma.
Plasma is about 90% water, but also contains proteins, nutrients, hormones and waste products. Blood is made up of about 60% plasma and 40% blood cells.
Each type of blood cell has a specific role to play:
- red blood cells carry oxygen around the body and remove carbon dioxide and other waste products; they give blood its red colour
- white blood cells are part of the immune system (the body's natural defence mechanism) and help fight infection
- platelets help the blood clot (thicken) to stop bleeding