How is the circulatory system related to the digestive system?

The products of the digestive system are actually tied directly to the circulatory system in that the organs of the digestive system are used to turn ingested food into products that can be absorbed by the blood and then carried to other organs for use as energy or other functions. There are also several links between the digestive system and the respiratory system in that there are organs and muscles that serve both, for example the diaphragm which works to force air into and out of the lungs as well as to force waste products out of the digestive system. All of the systems have to work together as well, without the intake of oxygen and exhalation of carbon dioxide, the function of the digestive system would grind to a halt. Without the production of glycogen and other things necessary for muscular function, produced by the digestive system and then distributed by the circulatory system, all three functions would cease.