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'''Blood''' is the a fluid of life. It that transports [[oxygen]] from the [[lungs]] to body tissue and [[carbon dioxide]] from body tissue to the lungs. Blood also transports nourishment from digestion and hormones from glands to all areas of the body. Blood also conveys disease fighting subtances to the tissues and waste to the kidneys. Blood is thicker than water and has a slightly salty taste. An adults body usually has 10 pints of blood circulating around. Blood is composed of billions of living blood cells floating in a liquid called plasma. If you took a small sample of this blood and poured it into a test tube and then put it in a machine called a centrifuge, you would be able to see the layers of this blood. This machine spins the blood around so fast that it separates the [[red blood cells]], from the [[white blood cells]], from the [[platelets]]. The red blood cells sink to the bottom because they are the heavier, more solid parts, but the plasma remains at the top because it is lighter. Plasma is 95% water and the other 5% is made up of dissolved substances including salts.