Composition of Bone in Animals: Organic and Inorganic Matter

The composition of bone consists of organic and inorganic matter. Roughly, it contains 30% organic and 70% inorganic matter, though this proportion varies among bones from different parts of the body.

Bone is a specialized connective tissue that plays a vital role in support, protection, movement, mineral storage, and blood cell production.

The proportion varies with age, and there is a high percentage of organic matter in growing animals, which is gradually replaced by inorganic matter.

Organic Matter

The organic matter in bone includes bone cells, collagen fibers, and the matrix, or intercellular substance.

Inorganic Matter

The organic matter chiefly consists of the fibrous protein—collagen, ossein, and chondroitin sulphate.

The organic part of bone contributes to the flexibility. It consists mostly of calcium phosphate (about 85%), and small amounts of calcium carbonate (10%), magnesium phosphate, sodium carbonate, and sodium chloride.

The major inorganic component of bone is calcium phosphate, mainly in the form of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂).

The inorganic salts are responsible for the rigidity and hardness of bone.