Are Bones Alive?

Bones have many living components, but the structural parts of bones, which are hard calcium phosphate salts in a network of collagen protein, are not living. Some of the living cells of bones deposit these materials around them to create the hard parts of the bones.

None of the structural components of bones are actually contained inside cells. The cells in bones also include marrow, which contains various cells that produce blood cells, along with blood vessels and nerves. Bones are constantly being built and broken down by the cells inside, but the hard parts of bones compose 80 percent of their mass.