An osteocyte is a type of cell that makes up bone. These cells are derived from osteoblasts, which are bone-forming cells. In general, they make up the majority of the mass of adult bone tissue in humans. Each cell within the bone tissue is typically connected to others, which work together to help create a strong matrix of living bone.
Bone tissue creation begins with osteoblasts. These cells create certain substances that help make up bone tissue, including collagen and other proteins. In some cases, once an osteoblast has finished creating the necessary substances to form bone, it gets surrounded by bone minerals and transforms into an osteocyte.
During its transformation from an osteoblast to an osteocyte, a space called a lacuna and canals called canaliculi form around the cell. The lacuna is surrounded by hardened bone minerals, such as calcium phosphate and calcium carbonate. Canaliculi serve as passageways for blood and nutrients to get through this hardened matrix. They also allow the cells to communicate with others nearby, by sending and receiving electrochemical signals.
In compact bone, this collection of bone minerals, canaliculi, and osteocytes housed inside lacunae typically form an osteon. Many osteons packed together help form compact bone tissue, which typically makes up the longer bones of the body, as found in the arms and legs. It also often helps form a hard, protective cover around other bones.
The other form of bone, spongy bone, also contains these cells, but the components are often more loosely connected. Rather than forming osteons, they typically form trabeculae. A loose network of trabeculae makes up the spongy bone tissue, which is found inside the ends of many bones, such as the crest of the hip.
Since osteocytes are living cells, they can die. In fact, the body is undergoes a more-or-less continual process of reabsorbing old bone and creating new tissue. This process helps keep bones strong throughout a person’s lifetime.
In cases where too many osteocytes and/or other bone minerals are reabsorbed into the body, a condition called osteoporosis can result. This condition causes bones to lose mass and become porous, meaning that the bones are not as strong and are often extremely prone to breakage. Currently, there is no osteoporosis treatment that focuses on osteocyte formation, but it is an area that some experts suggests future studies could investigate.