BCS0031 - Anatomy and Physiology: The Urinary SystemEvery cell in our body is like an engine. And, like the engine in a car for example, each cell requires fuel to run and also produces waste by-products that must be eliminated. The circulatory system delivers the fuel that cells require, including oxygen provided by the respiratory system and nutrients provided by the digestive system. The circulatory system also removes cellular waste by-products, including carbon dioxide, which is expelled from the body by the respiratory system, and waste by-products dissolved in water, which are filtered and eliminated by the urinary system. | 
