Glossary
osteocyte
An osteocyte is a mature bone cell, once an osteoblast, sealed inside the matrix it made — it maintains that matrix and senses load.
An osteocyte is a bone cell that has finished building and is now walled into the matrix it produced. Each sits in a small cavity, the lacuna, and reaches its neighbors through fine channels, so the cells stay connected in a network across the bone. That network reads the bone's load: the osteocytes sense where bone is strained and signal the osteoblasts to add material there, and the osteoclasts to remove it where it is not. That is why bone thickens where a person's activity loads it and thins where it does not — bed rest and time in space do exactly this. Because the cells live inside the matrix, they survive only as long as blood reaches them. A fracture that cuts the blood supply leaves dead bone in place, and it has to be resorbed before new bone can fill the gap.
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Related terms
- osteoblast — An osteoblast is the cell that builds bone: it lays down the new matrix and starts the mineral deposit that hardens it.
- osteoclast — An osteoclast is the large, multinucleated cell that breaks bone down, releasing calcium into the blood and reshaping the skeleton.
Source: The anatomy and physiology guide in this course, whose organ and tissue descriptions follow the US National Cancer Institute's SEER Training Modules and MedlinePlus consumer health pages. Both are US federal government material, not subject to copyright in the United States. The definition above is written for this course in our own words. (SEER Training Modules accessed 2026-10-26; definition written 2026-10-27)