Calcified bone interface showing cell layers

A transmission electron micrograph showing the layers of cells at the interface of calcified bone. The layer of cells across the middle are the osteoblasts. These cells are packed with endoplasmic reticulam (indicating protein synthesis) and are laying down the osteoid - uncalcified collagen matrix (above the osteoblasts). To the right is a developing osteocyte with a mature osteocyte visible in the top centre. The black material is calcified bone. Biomedical Image Awards 2001.