Blood is a liquid that is used to carry oxygen and nourishment (such as minerals) and energy (such as sugar) around the bodies of many animals. It also carries away wastes.
Blood is not red. Most of it is a watery liquid called plasma, which is pale yellow. Suspended in this liquid are many blood cells, most of which are red, which is why blood appears red.
Blood cells soak up oxygen as they pass through the lungs. Blood cells then carry oxygen to the body. Waste carbon dioxide is not carried by cells, but dissolves in the plasma. It seeps out when it reaches the lungs.
Blood is circulated around the body through blood vessels by the pumping action of the heart.
