Homeostasis is balance. The shortest answer to your essay is that these 3 systems remove toxins from the body. Some of these toxins are in the air & food we take in, and some are just waste products after we process food.
The digestive system takes the food we eat, pulls out the energy we need to move and live, and passes on the waste to be excreted. If it didn’t excrete the waste, toxins would build up in the body.
The urinary system maintains homeostasis by filtering toxins out of the blood, and deciding how much water should be retained or wasted, based on our blood’s chemistry.
Another part of the excretory system is our skin. We sweat out toxins from exercise.
I hope these ideas are helpful to get to through your essay.
