Skeletal muscles are also known as striped, striated, somatic or voluntary muscles. They are attached to the skeleton and respond quickly to stimuli, allowing for fast contractions but resulting in easy fatigue. Skeletal muscles give the body its shape and structure, as without the skeletal structure the body would have no form. The human skeletal system consists of an axial and appendicular skeleton, with the axial skeleton made up of 80 bones that protect organs and maintain an upright structure, while the appendicular skeleton has 126 bones and allows for body movement. Protection of important organs is the most critical function of the human skeletal system.