Osteocytes

Osteocytes are defined as cells embedded in the mineralized bone matrix and compose over 90%–95% of all bone cells. They are regularly dispersed throughout the mineralized matrix, connected to each other and cells on the bone surface through slender, cytoplasmic processes radiating in all directions but generally perpendicular to the bone surface. The cell processes or dendrites pass through the bone in thin canals, called canaliculi, which connect osteocytes with cells on the bone surface. These cells were originally defined by their location, not by their function as is the case for osteoblasts and osteoclasts. They are now defined by their many functions, for example, as endocrine cells that regulate osteoblasts and osteoclasts, and other organs. These cells regulate phosphate and calcium homeostasis through targeted effects on kidney and through their perilacunar remodeling. Also functioning as the mechanosensory cells of the skeleton, they are now defined as “the master regulators” of bone.