Put the steps of endochondral ossification in the correct order. Your lecture notes and book are both good resources for this question. The matrix calcifies and chondrocytes die. Chondrocytes hypertrophy and absorb the surrounding cartilage matrix. Bony collar forms. Periosteal bud invades cartilaginous shaft and forms primary ossification center. The hyaline cartilage model is formed by chondroblasts. Stem cells in perichondrium form osteoblasts..