ABSTRACT
The skeletal system, important to the body both biomechanically and metabolically, is made up of individual bones and the connective tissue that joins them. Bone is the main constituent of the system and differs from the connective tissues in rigidity and hardness. These characteristics of bone result from inorganic salts impregnating the matrix, which consists of collagen fibers, a large variety of noncollagenous proteins, and mineral. The rigidity and hardness of bone enable the skeleton to maintain the shape of the body; to protect the soft tissues of the cranial, thoracic, and pelvic cavities; to supply the framework for the bone marrow; and to transmit the force of muscular contraction from one part of the body to another during movement. The mineral content of bone serves as a reservoir for ions, particularly calcium, and also contributes to the regulation of extracellular fluid composition, particularly ionized calcium concentration. In addition, bone is a self-repairing structural material, able to adapt its mass, shape, and properties to changes in mechanical requirements and endures voluntary physical activity for life without breaking or causing pain.
