Caption

Osteocyte bone cells, coloured scanning electron micrograph (SEM). Osteocytes are mature bone cells. They develop from osteoblasts, and become embedded in the bone matrix as it develops, with long cytoplasmic extensions reaching into the bone tissue. The osteocytes help maintain the bone tissue by replacing old bone and minerals. Here, the minerals in the bone have been removed by embedding in resin and etching with perchloric acid. This reveals the spaces in the bone and the shape of the osteocyte cells.