How does the respiratory system work with the digestive system?

The body cells depend upon products of both the respiratory and digestive systems' functions in order to maintain themselves. To produce energy, cells burn nutrient molecule fuel in oxygen. The digestive tract provides the nutrient molecules, through the process of digestion, while the respiratory tract provides oxygen. As such, the two systems work together to give your cells the ingredients they need to produce energy, which they use to communicate, build cellular products and grow.