What is the connection between digestive, circulatory, urinary and respiratory system

The connection between mentioned physiological system of an animal is through "Nervous System" it is the system which controls every other organ by motor neurons & sensory neurons

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Through The Respiratory System, The Oxygen Enters The Body Then Is Transported As Oxyhaemoglobin To the Cells with the help of cardiovascular system. 

The Cardiovascular system relates with the digestive system for an optimum heart rate. The Digestive system produces Nutrients, with the help of the Cardiovascular system transports these nutrients where it is needed.

There For, That being said, The Human Body Is reached in healthy equilibrium if all these systems work together in harmony 
 

As what he you go get the hot dog ; )