The human body is made up of 12 unique systems. The systems work together to keep the body healthy and running. Without these systems, we couldn_t walk, talk, or digest food. Doctors spend years learning about the human body and how to treat it when something goes wrong. Illnesses and injuries prevent the body from functioning correctly. Knowing how the systems run helps us to stay in the best physical shape possible. For more information, read Hippocrates Father of Medicine, another book in the Mission: Science series.