Characteristics of growing bone surfaces.

Both bone-forming and bone-destructing cells may appear in different forms. This conclusion has been drawn as a result of compared observations from histomorphologic, histochemical and vital staining studies. The bone-forming cells may be cuboidal and situated in one or more rows along the bone surfaces, or may be flat. The type of cell reflects the rate of bone formation. The bone-resorbing cells may be big multinucleated cells or small mononucleated cells. The latter cell type is well-known from the literature although not referred to in textbooks of histology. Flat bone-forming cells and small mononucleated bone-resorbing cells resemble each other in the light microscope. Studies of bone growth with the aid of histomorphologic descriptions of cell types have to take this fact into account. Otherwise, erroneous conclusions may easily be drawn.