Investigating our body systems 4th grade students have been learning about our body systems: digestive, excretory, respiratory and circulatory. Have a look at the models they have created!Investigating our body systems 4th grade students have been learning about our body systems: digestive, excretory, respiratory and circulatory. Have a look at the models they have created!Investigating our body systems 4th grade students have been learning about our body systems: digestive, excretory, respiratory and circulatory. Have a look at the models they have created!