In the adult the muscles form about 35-40% of the body weight. All the muscles are divided into the muscles of the trunk, head, and extremities. Long, short and wide muscles form three basic groups. The long muscles compose the free parts of the extremities. The wide muscles form the walls of the body cavities. Some short muscles, of which stapedius [stǝ'pidjǝs] (стремечковая) is the smallest muscle in the human body, form facial musculature. The structure of the muscular fibers is different in different groups of muscles. The muscles consist of a mass of muscle cells. The muscular fibers are connected together by connective tissue. There are many blood vessels and nerves in the muscles. The muscles are the active agents of motion and contraction составить по этому тексту 3-4 вопроса