1. Osteon development Blood vessel Osteoclasts arrive begin dissolving a cone or “tunnel” in the mineralized matrix

2. Osteon development Osteoblasts now arrive line the “tunnel” begin adding layers of mineralized matrix

3. Osteon review Osteon (haversian system) Central canal Osteocytes Lamellae (in lacunae) Canaliculi

4. Osteon fun facts Around 21 million osteons in adult skeleton Each osteon is 100-400 µm in diameter (1 inch = 25,400 µm) A medium osteon has about 30 lamellae (each about 3 µm) The central canal is around 50 µm in diameter