Final answer:
The musculoskeletal system, comprising of skeletal muscle, represents about 42% of the body mass in the average adult male and 36% in the average adult female.
Step-by-step explanation:
The musculoskeletal system, which includes both muscles and bones, constitutes a significant percentage of the body's mass. Specifically, the skeletal muscle mass is about 42 percent of an average adult male's body weight and about 36 percent of an average adult female's body weight. Skeletal muscle is muscle tissue attached to bones by tendons and is responsible for voluntary body movements. It is the most common type of muscle tissue in the human body. These muscles are vital for movements such as locomotion, maintaining posture, and various voluntary movements. The musculoskeletal system is not only crucial for movement but is also important for the protection of internal organs and support of the body's structure.