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How does bone mineralization harden the collagen matrix of bone?
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bone disease
Defect of tibia, caused by septic osteomyelitis in childhood, with compensatory thickening of the fibula (right). Normal bones are shown at left.
Bone mineralization hardens the collagen matrix through the organized deposition of minerals, primarily calcium and phosphate in the form of hydroxyapatite crystals.12
This process occurs in two primary ways:
- Nucleation and Growth: Specialized cells called osteoblasts secrete an organic matrix known as osteoid and release matrix vesicles containing calcium and phosphate ions. These vesicles serve as nucleation sites where hydroxyapatite crystals begin to form. As these crystals grow, they extend beyond the vesicles and propagate into the surrounding collagenous matrix.1
- Structural Integration: The mineral crystals are arranged parallel to the long axes of collagen bundles, with many residing in voids within the bundles themselves.3
By dispersing these rigid, brittle crystals within the elastic collagen matrix, bone functions as a two-phase material. This intimate association prevents the propagation of stress failures, providing the bone with its characteristic hardness, rigidity, and compressive strength while maintaining necessary elasticity.3