osteoblast os·te·o·blast (ŏs'tē-ə-blāst')
A cell from which bone develops; a bone-forming cell.
A specialized bone cell that produces and deposits the matrix that is needed for the development of new bone and consists primarily of collagen fibers. Osteoblasts are formed from osteoclasts on the outer surfaces of bone and in bone cavities, and bone deposition takes place constantly in living bone. As new bone grows and hardens with the addition of calcium and phosphate, osteoblasts become embedded in the bone matrix and develop into osteocytes.