Biology of Bone and the Interaction of Bone with Other Organ Systems

摘要

Bone has essential functions to support and protect the soft tissues of the body and to enable locomotion. The formation and maintenance of bone is orchestrated by the three major cell types resident within it- osteoblasts, osteocytes and osteoclasts. These cells confer on bone its ability to respond to increased or decreased biomechanical requirements, bone matrix repair and to regulate a variety of extra-skeletal functions. For locomotion, bone is dependent on the actions of muscles, and bone also depends on the strains produced by muscles for its proper functioning. Unloading of bone results in rapid loss of bone mass, as seen in space flight or bed rest. Recent findings suggest that, in addition to biomechanical interaction, bone and muscle may also communicate biochemically. Bone also interacts closely with the vasculature and the nervous system, and is highly perfused and innervated. The latter suggests roles for the central nervous system in bone function, and this has increasingly been found to be the case. Vascular pathology also has implications for bone health, which is demonstrated in avascular bone necrosis and fracture non-union. Articulating joints in the skeleton depend on cartilage providing a fric-tionless surface and spreading load across the underlying bone. Thus osteoarthritis is a disease of the whole joint, with important effects in both bone and cartilage tissue compartments. This chapter will introduce the biology of bone tissue and discuss its interaction with muscle, cartilage, the nervous system and the vasculature, since all of these organ systems underpin an understanding of the biomechanics of bone.