Blood's three primary functions are to ward of diseases and infections, maintain the body's stable internal environment and transport important chemicals. The plasma, red and white blood cells and platelets that make up the blood help carry out these three functions.
Blood carries oxygen, carbon dioxide, nutrients, waste, heat and hormones throughout the body to each of its cells. Without blood, cells would fail to perform as needed to sustain life. Red blood cells are responsible for blood clotting, ensuring that most cuts do not cause major blood loss. White blood cells fight off infection and are a major component of the body's immune system.