These are just a few examples of the systems that primary students would be interested in exploring. Each of these systems should be learned, not only for its own individual function, but how it interacts and is dependant on the other systems within the body. Other systems such as the digestive system, the immune systems, and our skin would be appropriate systems to explore. I would decide which systems to explore, and how many to cover according to class dynamics and the length of time you are planning to spend on the unit.