Skeletal Development and Homeostasis

The first evidence of the developing axial and appendicular skeleton is seen during the embryonic period when mesenchymal cells condense in the areas of the future bones. Bone is formed through two fundamentally distinct mechanisms: endochondral ossification and intramembranous ossification. Growth plates facilitate bone length growth by the formation of new cartilage. Osteoblasts are the cells that synthesize new bone. They are derived from mesenchymal precursor cells and exist either as flat resting cells or as more metabolically active cuboidal cells. Periosteal trauma occurs either as a consequence of fracture, secondary to surgical manipulation of the bone, or as a consequence of bone pathologies such as infection or neoplasia. Reactive new bone is a relatively common radiographic finding and a not uncommon confounding factor in bone biopsies taken from sites of bone pathology.