FIG. 1.

Anatomic location of the physis (or growth plate) in long bones. The physis is a cartilaginous region located between the epiphysis and the metaphysis at each end of long bones. Marrow compartments serve as a source of nutrition with vessels feeding the growth plate cartilage. The juxtaposition of hard cortical bone against relatively softer cartilage forms a weak point in the pediatric skeleton. (Expanded section): Five cartilaginous zones of the physis. Resting zone chondrocytes give way into rapidly proliferating chondrocytes that form vertical stacks in the proliferating zone. Cells in the hypertrophic zone enlarge by producing glycogen. In the calcification zone, chondrocytes undergo apoptosis and the extracellular matrix calcifies forming a network for osteoblasts to invade and form new bone in the ossification zone.