ABSTRACT
Bone and cartilage are specialised connective tissues that combine extracellular matrix biomolecules and complexes of inorganic ions to give mechanically com petent and structurally durable materials that meet functional requirements. The formation, development and maintenance of these tissues throughout life are dependent on the coordinated activity of several different cell types. In childhood and young adult life, bone growth is an important determinant, which appears to have a strong hereditary component with other influences including diet, exercise and, in some cases, chronic illness. In old age, the decrease in bone mass is associated with progressive sarcopenia and decreased physical activity and may be promoted by hyperparathyroidism, associated with vitamin D deficiency. As the skeleton ages, there is a marked decrease in bone mineral density that correlates with increased fracture risk. With age, there is a remarkable reduction in the number of trabecular bone struts and consequent loss of their connectivity.
