Fine structure of bone matrix calcification

Various functions of bones are derived from the characteristics that they calcify. In bone calcification, hydroxyapatite is crystallized on the type I collagen-based organic matrices. The organic components of those bone matrices are commonly shared with other fibrous tissues. As extracellular fluid supersaturates hydroxyapatite, the reasons why bones are specifically calcified remains enigmatic. With the bone matrix calcification, the structural and the spatial changes of those organic substances seem to be closely associated, and participate in the complicated regulation of hydroxyapatite multiplication. The present paper overviews the morphological findings of bone calcification, and discusses the mineral and organic environments in bone matrix calcification.