The respiratory system works to get essential materials to the cells when we breathe it takes the carbon dioxide from the alveoli ( air pockets in our lungs) and replacing it with oxygen. The circulatory system takes consists of veins which carries oxygenated blood from the entire body to the heart, and arteries which takes deoxygenated blood away from the heart to the lungs. Finally the digestive system works to get essential materials to the cells when we eat the vitamins, minerals and nutrients not only go to certain organs but also through the blood and the cycle starts all over again.