Bone Cells and Tissue

Bone or osseous tissue comprises four main cell types — osteogenic cells, osteoblasts, osteocytes, and osteoclasts.

Osteoclasts are derived from the hematopoietic lineage, whereas all other cells are from the mesenchymal lineage.

The osteogenic or osteoprogenitor stem cells reside in the inner membrane of the periosteum and the endosteum.

They are mitotically active and can differentiate into osteoblasts in response to appropriate signals.

Osteoblasts are cuboidal cells that synthesize collagen and calcium-binding proteins, forming the uncalcified matrix called osteoid.

As the osteoid mineralizes into hard bone matrix, the buried osteoblasts mature into osteocytes.

These oblong cells develop long, dendritic processes to communicate with other osteocytes via gap junctions.

Osteocytes help maintain the osseous tissue and regulate bone deposition by osteoblasts and bone resorption by osteoclasts.

Osteoclasts are large, multinucleated cells with a ruffled border, increasing the surface area for releasing acids and enzymes that digest the components of the matrix.

Together, these cells regulate bone tissue, facilitate bone repair, and maintain calcium homeostasis in the body.