Editing Human skeleton (section)

===Storage===
The [[Osteon|bone matrix]] can store [[calcium]] and is involved in [[calcium metabolism]], and [[bone marrow]] can store [[iron]] in [[ferritin]] and is involved in [[Human iron metabolism|iron metabolism]]. However, bones are not entirely made of calcium, but a mixture of [[chondroitin sulfate]] and [[hydroxyapatite]], the latter making up 70% of a bone. Hydroxyapatite is in turn composed of 39.8% of calcium, 41.4% of oxygen, 18.5% of phosphorus, and 0.2% of hydrogen by mass. Chondroitin sulfate is a sugar made up primarily of oxygen and carbon.{{Citation needed|date=September 2024}}