The three different Zones of periosteum; Zone 1 has an average thickness of 10–20 um consisting predominantly of osteoblasts; the majority of cells in Zone 2 are fibroblasts, with endothelial cells being most of the remainder. Zone 3 has the highest volume of collagen fibrils among all the three zones. The bottom of the figure shows regenerative capacity of the periosteum to form different cell types.
