The blood transports oxygen, carbon dioxide, nutrients, water, hormones, waste substances and heat. The waste substances are moved to the liver and kidneys, which remove toxins from the blood. Urea is moved from the liver to the kidneys.
Oxygen is transported to organs to keep them healthy, while carbon dioxide is moved back to the heart and lungs. Nutrients gleaned from digestion, such as vitamins and minerals, are moved to the various organs that need them. Hormones are moved to the areas where they are needed from the places they are made. Heat is transported to places like the skin to keep the body at the correct temperature.