Blood has four main components: plasma, red blood cells, white blood cells and platelets. Blood has many different functions, including:
- Transporting oxygen and nutrients to the lungs and tissues
- Forming blood clots to prevent excess blood loss
- Carrying cells and antibodies that fight infection
- Bringing waste products to the kidneys and liver, which filter and clean the blood
- Regulating body temperature
The blood that runs through the veins, arteries and capillaries is known as whole blood, a mixture of about 55 percent plasma and 45 percent blood cells. About 7-8 percent of your total body weight is blood. An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about 9 pints.