The five chief functions of the skeleton are protection, shape, support, movement and blood production. The skeleton comprises the vital underlying structure of the body.
The skeleton's primary function is to form a solid framework that supports and protects the body's organs and anchors the skeletal muscles. The bones of the axial skeleton, which runs along the body's midline axis, act as a hard shell to protect the internal organs from damage caused by external forces. The bones of the appendicular skeleton, which can be found in the limbs and girdles, provide support and flexibility at the joints and anchor the muscles that move the limbs.
The bones of the skeletal system are attached to the skeletal muscles of the body. Almost every skeletal muscle works by pulling two or more bones either closer together or further apart. Joints act as pivot points for the movement of the bones.
Red bone marrow, which is found in the hollow space of bones, produces red and white blood cells in a process known as hematopoiesis. Children tend to have more red bone marrow compared to their body size than adults do, due to their body’s constant growth and development. The amount of red bone marrow drops off at the end of puberty, replaced by yellow bone marrow.
At birth, the skeleton of a newborn has more than 300 bones; as a person ages, these bones grow together and fuse into larger bones, leaving adults with only 206 bones.