The Skeletal System:
You use the skeletal system when you walk, stand, run, jump, etc. It is made of all the bones in our body. God made it so that we would not only be a pile of jelly.
The Muscular system:
You use the muscular system when you lift weights do pushups and more. It is made up of all your muscles.
The Digestive System:
You use the digestive system when you eat pizza, chicken, when you drink milk, etc. It is made of the mouth, stomach, small intestines, etc. It was created to help you digest food.
The Nervous System:
You use the nervous system when you get punched, stabbed, get a limb broken, etc. Some parts of the nervous system are the brain, the nerves, and the spinal cord.