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Bone remodeling
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Bone looks like a finished piece, but it is not: it changes. That change is called bone remodeling, and it happens in two steps that go in order. First, old or damaged bone is resorbed, meaning it is dissolved and carried away. Then new bone is laid down in its place. Bone is never finished; it rewrites itself.
Two cells with opposite jobs handle this, plus a third that takes part. The osteoclast is the one that tears down: it breaks apart the bone matrix with lysosomal enzymes, which are digestive enzymes, and with hydrogen ions, which turn the matrix acidic. The osteoblast is the one that builds: it fills the space left behind with new collagen and mineral. The osteocyte, the cell that lives trapped inside bone that has already formed, also takes part in the process.
All of this serves several purposes. Bone adapts its architecture to what the body is asking of it, repairs microdamage, and helps maintain the body's calcium and phosphorus balance.
In brief
Bone remodeling is how the skeleton changes: old or damaged bone is resorbed, then new bone is laid down.
Bone is never finished; it rewrites itself.
Two cells do the work, with the osteocyte taking part: osteoclasts break down the matrix with lysosomal enzymes and hydrogen ions, and osteoblasts fill the gap with new collagen and mineral.
This lets bone adapt its architecture to demand, repair microdamage, and help keep calcium and phosphorus in balance.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Bone Remodeling, StatPearlsPublished
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