How do body systems interact with each other?

There are 11 different organ systems in the human body and each system must work with all other systems in order to sustain life for the individual. Some work more closely with others, but they all must interact. Some examples include:

Respiratory and Circulatory systems: Your respiratory system includes your airways from your mouth and nose to your lungs. Its major job is to bring in oxygen and release CO2 from your system. Oxygen is needed in every cell of the body in order to use ATP and fuel the body, without it our cells could not take their stored energy sources and actually use the energy. To get the oxygen around our body our alveoli (little popcorn-shaped structures in our lungs) drop it off in capillaries, tiny blood vessels, that surround them. This is where the circulatory system takes over, which includes your blood, blood vessels, and your heart. Your blood is a super highway and a connective tissue, connecting every living cell in the human body. All things, especially oxygen and fuel, are sent along your blood in order to feed the body. The heart pumps the blood around the body and red blood cells carry the oxygen to the cells. As the cells are using up energy, they create carbon dioxide (CO2) which is toxic and needs to be released. The blood picks this up and takes it back to the lungs to be released with your exhales. 

Muscular and Skeletal systems: This one is a bit easier to conceptualize. Your skeleton has many jobs, but one of its biggest is to support your body and give you shape, structure, and to help you move. Your muscles work around joints, or places where 2 or more bones meet, and pull the bones around the joints. This causes your body to move. Without bones to tug at, the muscles would just contract and writhe uselessly. Without muscles to pull on them the bones could not move and would be at the mercy of any outside forces. 

There are many other examples you could use to help understand. A few systems, like the circulatory and the nervous, interact with every system in the body and are completely interconnected. Other systems, like the urinary (excretory) or the lymphatic, may be more paired to one or 2 systems, but they still require other systems to fully perform their functions. Just like in large scale factories or businesses it takes many different departments and parts in order to make sure the operation is working at its best. I hope this helps!