Chemical composition

The organic matrix and the mineral substance are the two components of calcified bone matrix. The organic components of bone include the five major cells of bone and osteoid. One third of the matrix consists of osteoid, with ground substance as proteoglycans and glycoproteins and collagen fibers. The basic building blocks of bone are the mineralized collagen fibril. Bone consists of 90% 8 of collagen I fibrils. Collagen I fibrils act as a framework; contribute to the flexibility and tensile strength because of the intra- and intermolecular cross-links of the molecules. These collagen fibers allow resisting stretch and twisting. The mineral substance is calcium phosphate hydroxyapatite. Present as needle-like crystals around and in collagen fibers. The hardness of the crystals allows resisting compression.1,8,13