ABSTRACT
Humans and vertebrates both share in common a regional division of the body into head, trunk, and extremities. The structure of the head differs from that of the trunk in that there is an absence of segmental organization. The induction center of the anterior head region for the nose, the eyes, and anterior skull base is subject to the influence of the frontal brain, the prosencephalon. Bone formation can ensue in two ways, either through desmal ossification or through chondral ossification. The activities of osteoblasts and osteoclasts are crucial to the formation of bone as well as to its constant remodeling and regenerative capabilities. The mesenchyme becomes concentrated into an envelope around the brain vesicles from which the skull bones arise partly through chondral and partly through desmal ossification. Skull morphogenesis is controlled by a genetic program modifiable by environmental factors. Genes which attack cartilage or bone can lead to morphogenic skull changes.
