The human body contains approximately 640 muscles. These muscles are responsible for a variety of movements, including both voluntary and involuntary movements. The muscles are made up of muscle fibers, which are long, thin cells that contract in response to signals from the nervous system. The muscles are also surrounded by connective tissue, which helps to support and protect them. Some of the major muscle groups in the body include the biceps, triceps, quadriceps, hamstrings, and glutes, as well as the muscles of the chest, back, and abdomen. Regular exercise can help to strengthen and tone these muscles, which can improve overall health and fitness.