Endochondral ossification
- An INDIRECT form of ossification, wherein a hyaline cartilaginous model (template) is replaced with bone, such as occurs with long bones (eg, the femur).
Endochondral Ossification
- * Mesenchymal cells migrate and differentiate to form a hyaline cartilage model, which comprises basophilic collagen and ground substance.
- Chondrocytes hypertrophy, which signals (via vascular endothelial cell growth factor) the sprouting of blood vessels, which we'll draw next.
- Periosteal buds invade the center of the diaphysis. Vascularization occurs via the periosteal bud, which brings forth osteoprogenitor cells and forms the primary ossification center, which forms within the cavities that are created when the hypertrophic chondrocytes starve and apoptose (die).
- Vasculature further invades the primary ossification center and the osteoprogenitor cells remodel bony matrix as the ossification center grows linearly (via interstitial growth).
- Medullary cavity forms as the primary ossification center degenerates cavitates and remodels via interstitial growth. Vasculature invades the cavity to fill it with marrow. .
- There is an epiphyseal (growth) plate at the border of the metaphysis and the epiphysis: elsewhere we learn about the zones and processes of interstitial growth.