1. New osteons are constructed on outside of bone 2. Osteoblasts from periosteum add new bone tissue, enclosing a blood vessel running through periosteum 3. Once blood vessel's enclosed, periosteum becomes endosteum inside the newly formed canal 4. Osteoblasts in endosteum continue to make more bone tissue in concentric rings resulting in a new osteon 5. While new bone is being made on outside of bone, osteoclasts in medullary cavity endosteum destroy bone lining marrow cavity