Three distinct types of bone cells are present in bone tissue, each with their own crucial function. Working together, osteoblasts, osteoclasts and osteocytes are responsible for proper development and maintenance of the skeleton, as well as regulating levels of minerals present in the bloodstream and throughout the body. Two other types of bone cells also are worthy of mention. Lining cells and osteogenic cells, though both derived from osteoblasts, also have their own key functions for proper bone health.

Osteoclasts are large bone cells formed in the marrow of the bone. These cells are made from fused cells and have multiple nuclei. They are similar in structure to white blood cells. Responsible for breaking down bone tissue, these bone cells perform an essential role in bone growth and healing.

Osteoblasts are the bone cells responsible for the creation of new bone tissue. These cells are also found in the marrow of the bone. Working collectively, osteoblasts produce bone tissue called an osteoid from collagen and calcium, building outward from the marrow. They also attract calcium and mineral deposits to the osteoid. These minerals give the bone its rigid structure.

As bone tissue is generated, new bone tissue fills in these cavities, and the osteoblasts lining the osteoid are squeezed flat. Old osteoblasts are called lining cells and no longer produce new tissue. Instead, they provide protection for the underlying bone matrix. They also are key in regulating levels of minerals such as calcium and phosphate, allowing these substances to pass into and out of the bone tissue as needed.

When creating bone tissue, not all osteoblasts become lining cells. Some remain deep in the bone matrix and become osteocytes, cells with long branches through the bone tissue that form a network. Osteocytes function as a control center, directing mineral deposits and repairing damage to the bone tissue as needed. They also are responsible for releasing minerals such as calcium into the bloodstream to maintain good health.

Most bone cells such as osteoblasts, osteoclasts and osteocytes are unable to divide and cannot reproduce. Osteogenic cells are bone cells capable of creating new osteoblasts and osteoclasts. These bone cells are located in the periosteum and the bone marrow, and they are responsible for generating new bone cells. An injury such as a fracture triggers cell production by the osteogenic cells, creating new osteoblasts and osteocytes to repair the damage as quickly as possible.