Blood is the reddish liquid that circulates around your body. It carries oxygen and food to body cells, and takes carbon dioxide and other waste away. It fights infection, keeps you warm, and distributes chemicals that control body processes.
Blood is made up of red cells, white cells and platelets, all carried in a liquid called plasma.
Plasma is 90% water, plus hundreds of other substances, including nutrients, hormones and special proteins for fighting infection.
Blood plasma turns milky immediately after a meal high in fats.
Blood platelets are tiny pieces of cell that make blood clots start to form in order to stop bleeding. Blood clots also involve a lacy, fibrous network made from a protein called fibrin. Fibrin is set in action by a sequence of chemicals called factors (factors 1 through to 8).
The amount of blood in your body depends on your size. An adult who weighs 80 kg has about 5 litres of blood. A child who is half as heavy has half as much blood.
A drop of blood the size of the dot on this i contains around 5 million red cells.
If a blood donor gives 0.5 litres of blood, the body replaces the plasma in a few hours, but it takes a few weeks to replace the red cells
Most people’s blood belongs to one of four different groups or types – A, 0, B and AB.
Blood type 0 is the most common, followed by blood group A.
Blood is also either Rhesus positive (Rh+) or Rhesus negative (Rh-). Around 85% of people are Rh+. The remaining 15% are Rh-.
If your blood is Rh+ and your group is A, your blood group is said to be A positive. If your blood is Rh- and your group is 0, you are 0 negative, and so on.
The Rhesus factors got their name because they were first identified in Rhesus monkeys.
A transfusion is when you are given blood from another person’s body. Your blood is ‘matched’ with other blood considered safe fin- transfusion.
Blood transfusions are given when someone has lost a lot of blood due to an injury or operation. They are also given to replace diseased blood.