This slides demonstrates how bones elongate. Hyaline cartilage in the lower resting zone will divide rapidly mitotically in the zone of proliferation, enlarge in the zone of proliferation, and die in the zone of calculation. The zone of ossification occurs when fibroblast invade the remaining matrix of the zone of calcification and differentiate into osteoblasts. These in tern, produce bone and become osteocytes.
In the zone of hypertrophication, which rest below the zone of proliferation, the cartilage cells take on extra glycogen and enlarge. The zone of calcification reveals a calcified matrix devoid of chondrocytes on which osteobasts cells will attach to form woven bone. Note the deep pur-ple "spicules" of calcified matrix. Lastly, the zone of ossification is where true bone develops and is remodeled.