Why is the inter-relationship between the digestive, respiratory and cardiovascular system essential?

- in order for humans to survive

and discuss role of tissue fluid.Why is the inter-relationship between the digestive, respiratory and cardiovascular system essential?Wow, this is a fairly thick question. The systems of the body are pretty complicated and most have roles to play in homeostasis that are different than their primary function. The digestive system alone has a role in nutrition, pH balance, osmotic balance, immune function, etc.



In a nutshell, the digestive system is responsible for taking all manner of edibles and breaking them down into their constituent pieces. Carbohydrates, fats, proteins and nucleic acids are broken into short fragments that can be transported throughout the body and made into new cellular material. The circulatory system consists of vessels, a pump and a liquid tissue: blood. The composition of blood is unique in that nutrients can dissolve into it and be carried to where they're needed. The blood carries oxygen from the lungs and nutrients liberated by the digestive system to just about every square inch of your tissue.



Once in the tissues, small particles can simply move out of the blood, into the extracellular fluid, and then into the cells. Larger nutrients require more complicated means of leaving circulation, but that's a conversation for another time. Needless to say, oxygen and nutrients get into the cell at some point. Mitochondria within the cell use the oxygen, some fats and sugar to produce ATP, the main energy molecule in human cells. The ATP can then be used to fuel the work that the cell does-- converting basic fats, proteins and nucleic acids into new cells, organelles, hormones etc.

Without a way to capture specific molecules from our environment and efficiently move them to all of our trillions of cells, human life would not be possible. Those three systems essentially run the furnace that keeps the rest of the body ticking.

Sorry if this seems overly complicated or overly simplified, from the question it's hard to gauge how in-depth of a response you wanted.