ABSTRACT
Bone is the most highly differentiated and specialized of the supporting or connective tissues. Bone develops by ossification of connective tissue, by osseous transformation or replacement of cartilage, or by a combination of these two processes. Bone tissue is formed by the process of apposition of new bone upon connective tissue, cartilage, or bone. A fracture of mature cartilage sometimes becomes united by permanent fibrous tissue, and sometimes some of its fibrous tissue is replaced by bone rather than cartilage. The process of endochondral bone growth is radiosensitive because of the radiosen-sitivity of growing cartilage and bone marrow. The rising radioresistance of the growing cartilage with increasing age is associated with a lesser degree of change in radiosensitivity of the marrow and fine vasculature with age. Radiation doses of moderate size cause submaximal damage to the cartilage plate that varies in degree with the size of the dose.
