Osteocyte

An osteocyte, a Jewish-star shaped cell, is the most comonnly found cell in mature bone, and can live as long as the organism itself. Osteocytes have an average half life of 25 years(Full life of 50 years), they do not divide, and they are derived from osteoprogenitors, some of which differentiate into active osteoblasts. In mature bone, osteocytes and their processes reside inside spaces called lacunae and canaliculi, respectively. Cells contain a nucleus and a thin ring of cytoplasm. When osteoblasts become trapped in the matrix they secrete, they become osteocytes. Osteocytes are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi, which are used for exchange of nutrients and waste through gap junctions. The space that an osteocyte occupies is called a lacuna (Latin for a pit). Although osteocytes have reduced synthetic activity and, like osteoblasts are not capable of mitotic division, they are actively involved in the routine turnover of bony matrix, through various mechanosensory mechanisms. They destroy bone through a rapid, transient (relative to osteoclasts) mechanism called osteocytic osteolysis. Osteoblasts/osteocytes develop in mesenchyme. Hydroxyapatite, calcium carbonate and calcium phosphate is deposited around the cell.