Composition of the Bone Matrix

The human femur is a composite material approximately 70% of its matrix is inorganic hydroxyapatite, 20% is organic, and 10% is water (Kaplan 

The inorganic component of bone is primarily platelike (20 to 80 nm long and 2 to 5 nm thick) crystalhne hydroxyapatite, Ca5(P04)3(0H) or HA (Kaplan et al., 1994 Park and Lakes, 1992). Small amounts of impurities may be present in the mineralized HA matrix for example, carbonate may replace phosphate groups, whereas chloride and fluoride may replace hydroxyl groups. Because release of ions from the mineral bone matrix controls cell-mediated functions, the presence of impurities may impact important biological aspects (and, subsequently, affect chemical and mechanical properties of bone) that are critical to normal bone function for example, impurities present in the mineralized matrix may affect cellular function(s) that influence new bone formation (Kaplan et al., 1994 Park and Lakes, 1992). 

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