Section One: Epiphyseal Bone Formation ! Section Two: Diaphyseal Bone Formation ! Section Three: Cortical Remodeling Section One Epiphyseal Bone Formation

The vast majority of the longitudinal growth of a typical mammalian long bone occurs at the ends of the bone in platelike structures termed growth plates. Both growth plates, one at the proximal end and the other at the distal end, are peripheral extensions of the primary center of ossification, a structure that arises in the midportion of the cartilaginous anlage of the bone-to-be during early fetal life. Originally the primary center of ossification grows and expands centrifugally in all directions. However, as it continues to expand, endochondral bone growth soon becomes confined to the growth plates (Fig. 2-1).