Three Dimensional Ultrastructural Changes of the Cortical Bone Surface with Aging

抄録

The diaphyses of femurs obtained from crab-eating monkeys (6 months old, 3 years old and about 20 years old) were examined with a high-resolution scanning electron microscope in order to observe three dimensional ultrastructure of the surface matrix of cortical bone. Specimens were treated by trypsin solution to digest both osteoblasts and amorphous organic matrix on the bone surface. The superficial matrix of the immature bone was composed of collagen fibrils with dense reticular structure. Under the sparse reticular collagen fibrils, the collagen fibrils running in a uniform direction were observed. At the surface of mature bone, the collagen fibrils running in a roughly uniform direction to the long axis of the bone were observed and these collagen fibrils formed bundles. Microgranules attaching on the very compact collagen fibrils were found at the surface of mature and senile bone. At the surface of senile bone, the collagen fibrils were almost buried by homogeneous granular bone matrix. It is considered that the microgranules were the calcified granules constructed by crystals of hydroxyapatite.