How are the circulatory and digestive systems related?

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 provide energy to other organs related to the circulatory system such as the heart.

Without the transport of oxygen to the organs of the digestive system and removal of carbon dioxide from their tissues by the circulatory system, the operations of the digestive system would ground to a halt.

So the digestive system makes available products that supply energy to the circulatory system and the circulatory system  brings oxygen vital to the organs of the digestive system and keeps it running and at the same time carries away waste thus maintaining smooth function.