Bone is a vital, dynamic connective tissue whose structure and composition reflect a balance between its two major functions: provision of mechanical integrity for locomotion and protection, and involvement in the metabolic pathways associated with mineral homeostasis. In addition, bone is the primary site of haematopoiesis, and a rich picture of the complex interplay between the bone organ system and the immune system continues to emerge.
Bone as a tissue consists of the mineralized and nonmineralized (osteoid) components of the
cortical and cancellous regions of long and flat bones.There are three cell types on (and in) bone tissue: (1) the bone-forming osteoblasts, which when engulfed in mineral become (2) osteocytes, and (3) the bone-destroyingosteoclasts. Each of these cells communicates with one another by either direct cell contact or through signalling molecules, and they respond to each other.
Bone metabolism is regulated by multiple environmental signals including chemical, mechanical, electrical, and magnetic. The local cellular compartment of the bone responds to these environmental signals by modulating the balance between new bone formation and the local resorption of older bone (i.e., remodeling).