Different types of bone cells can create, maintain and dissolve bones. There are two main categories of bone cells: forming cells and resorbing cells.
Bone forming cells fall under two types: osteoblasts and osteocytes. Osteoblasts come from bone marrow and produce proteins that calcify to form solid bones. They also receive hormones and vitamins from the rest of the body. In addition, they can secrete proteins and factors that communicate with other cells in the body. When osteoblasts are finished forming bones, they either transform into other types of bone cells or dissolve. The ones that transform into other kinds of cells become either osteocytes or bone lining cells.
Osteocytes are responsible for maintaining bones. They are located inside of the bones and communicate with osteoblasts and bone lining cells to keep bones healthy. Scientists are still working to understand exactly how osteocytes work, but many believe that they respond to changes in the bone and stimulate other types of bone cells to react to those changes.
Bone resorbing cells are called osteoclasts. Resorbing is a dissolving process; osteoclasts give off enzymes and acids that wear away at bones to dissolve them. This usually happens when extra proteins and tissue calcify to form extra bone. When they are finished resorbing, they die.
Bone lining cells are not part of bones themselves, but they play an important role in bone health. These cells distribute calcium from the bones into the blood, receive hormones from the body that promote bone growth and resorbing and prevent harmful chemicals from entering the bones.