What are the main functions of the muscular system? Muscles play a part in every function of the human body, from circulation to mobility. The muscular system is made up of over 600 muscles. These include three muscle types: smooth, skeletal, and cardiac. Only skeletal muscles are voluntary, meaning you can control them consciously. Smooth and cardiac muscles act involuntarily. Each muscle type in the muscular system has a specific purpose. You're able to walk because of your skeletal muscles. You can digest because of your smooth muscles.