Carries oxygen from lungs to all body cells, Carries CO2 from all body cells to the lungs, Takes wastes (ex. ammonia, uric acid, urea) from body cells to kidney, Helps maintain body temperature and pH levels, Heals wounds by blood clots, Fights infections by pathogens, white blood cells make antibodies, Transport control chemicals (ex. hormones), Takes nutrients from the duodenum to all body cells (ex. Amino acids, simple sugars, fatty acids)