The skeletal system is composed of 206 bones that perform several important functions. The skeleton is divided into the axial skeleton, which includes the skull, vertebral column, and rib cage, and the appendicular skeleton, which consists of the upper and lower limbs. Bones provide structure and support to the body, protect internal organs, allow for movement through joints with muscles, store minerals, and produce blood cells. Bones are classified by their tissue composition as either compact or spongy bone, and by their shape as long, short, flat, or irregular.