Figure 9. Bone Development. Schematic diagram showing the initial stages of endochondral ossification. Bone development begins with mesenchymal condensation to form a cartilage model of the bone to be formed. Following chondrocyte hypertrophy and cartilage matrix mineralization, osteoclast activity and vascularization result in the formation of the primary, and then secondary ossification centers. In mature adult bones, the growth plate is fully resorbed, so that one marrow cavity extends the full length of the bone. See text for details.