Functions and Organization of the Muscular SystemThe major function of the muscular system is to allow movement. As we noted in Chapter 13, muscle tissue can be classified as one of three major types: skeletal, smooth, or cardiac. Individual muscles, composed of a particular type of muscular tissue as well as connective and nervous tissue, are the organs of the muscular system. Skeletal muscles are responsible for the movements of bones and are under voluntary control. Smooth muscles facilitate the movement of substances through the body (e. g. food in the digestive tract or blood in a vein), while cardiac muscle (the myocardium) is found exclusively in the heart and provides the driving force for the movement of blood in the cardiovascular system. Both cardiac and smooth muscles are under involuntary control. By weight, muscle tissue, particularly skeletal muscle, is the most prevalent tissue in the body.