Blood

Blood is a fluid that transports oxygen and nutrients around the body in many animals and humans and consists of both red blood cells, white blood cells, plasma, and platelets. An average adult human has about 5 liters of blood circulating in their body.

Components of blood:
 * Red blood cells – their main role is to transport oxygen
 * White blood cells – the cells of the immune system which defend the body against infections
 * Platelets – important for blood clotting and tissue repair
 * Plasma - the liquid part of the blood which carries the blood cells and other substances around the body.