ˌperēˈästēəm noun
( plural perios·tea -ēə)
Etymology: New Latin, from Late Latin periosteon, from Greek, neuter of periosteos around the bones, from peri- + osteon bone — more at osseous
1. : the membrane of connective tissue that closely invests all bones except at the articular surfaces and is made up of an outer fibrous layer that furnishes attachment for muscles and an inner layer that furnishes osteoblasts and contains blood vessels by which the bone is nourished
2. : the vascular areolar tissue lining the marrow cavity of a bone — called also internal periosteum