The document discusses the three main types of muscles in the body - skeletal, smooth, and cardiac muscles. Skeletal muscles are striated and help the body move by holding bones and allowing movement. Smooth muscles are involuntary and found in internal organs. Cardiac muscles are found only in the heart and pump blood throughout the body. Muscles work with bones to allow movement and provide shape to the body. Exercise, healthy eating, and brain signals help muscles function properly. Without muscles, the body would be unable to move, breathe, or pump blood.