A Closer Look At Bones HAPBone Cells 1. Osteoprogenitor Cells = stem cells 2. Osteoblasts: build bone 3. Osteocytes: maintain bone matrix – Come from Osteoblasts 4. Osteoclasts: break down bone – to release Calcium and Phosphate – to respond to forces placed on bone Bone Formation • Ossification = process of bone formation – occurs in utero • Osteoblast’s role: - build bone - after an osteoblast becomes surrounded by bone matrix it becomes an osteocyte