Let us carefully define them. But body and environment also differ in some of their characteristics and doings. They define the en factors. They do it in their own terms.
Some monkeys live in trees, others on the ground.
The spectator defines these en factors as there, separately from the animal. Body and en are one event, one process. Either way it is one event, viewed as en or as body. Air coming in and lungs expanding cannot be separate. The point is that we need not split between the lungs and air.