BONE TISSUE CELLS
Bone resident cells arise from two different cell lineages, the osteoblastic lineage and the osteoclastic lineage.
The osteoprogenitor cells (or osteoprogenitors) are the stem cells of the osteoblastic lineage.
The osteoprogenitors reside in:
– the innermost layer of the periosteum, a connective tissue layer that surrounds most of the outer bone surfaces.
– the endosteum, a very thin cell layer that covers the surfaces of bone inner cavities.
The osteoprogenitors differentiate into osteoblasts that secrete and are surrounded by the bone extracellular matrix and become osteocytes, the adult cells of bones.
The osteoclasts, evolve from cells of a monocytic lineage established in the bone marrow and reach the bones through the blood circulation. The osteoclasts result from the fusion of these cells of monocytic lineage, resulting in large multinucleated cells.