The three main cell types of the osseous tissue are the osteoblasts, the osteocytes and the osteoclasts. Osteoblasts are known as bone-forming cells since they are the cells that secrete the proteinaceous part of the bone matrix (collagen, glycoproteins and proteoglycans). The bone matrix is the intercellular space where the mineral substances of the bones are deposited. Osteocytes are differentiated mature osteoblasts formed after these cells are completely surrounded by the bone matrix. Osteocytes have the function of supporting the tissue. Osteoclasts are the giant multinucleate cells that remodelate the osseous tissue. They are originated from monocytes and they contain many lisosomes. Osteoblasts secrete enzymes that digest the osseous matrix creating canals throughout the tissue.