immature bone cells Mature bone cells: Bone makers Maintain the extracellular matrix Bone stem cells Bone breakers Turn into osteocytes when trapped by their own secretions Located in periosteum \&e endosteum Located in lacunae Located wherever bone is being broken down Secrete extracellular matrix Made of calciurn minerals anchored to collagen fibers, within a seme-solid ground substance Arranged in lamellae Connected to other celis by canaliculi.