An ultrastructural study of phagocytosis in bone by osteoblastic cells from fetal mouse calvaria in vitro.

Twenty per cent of mature osteoblastic cells from parietal bone fragments in the mineralizing bone matrix phagocytized collagen fibrils. Forty per cent of immature osteoblastic cells in the partially mineralizing osteoid phagocytized collagen fibrils and mineralized bone particles. This phenomenon was most marked in cells containing a lake of glycogen. Thus during bone formation in vitro, osteoblasts may phagocytize bone-tissue components as well as synthesizing them.