Micromorphological aproaches to bone resorption and formation

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In this study, mice were used. Bones were exzamined by scanning electron microscory.1) To decrease the bone volume, the sciatic never and femoral nerve were cut at 3 weeks of age and the femur was observed after nerve cutting. The femur showed activation of bone formation 1 to 2 weeks after nerve cutting and a decrease of spongy bone due to bone resorption in 2 to 5 weeks. The bone grew to normallength but thin bone with pooly developed spongy bone. 2) To increase the bone volume, estradiole was injected at 4 weeks of age. The femur showed a marked decrease of spongy bone with in 3 days after injecion and then spongy bone inreased in density and amount to occupy the marrow spaces. 3) Osteoclasts were classified into two types according to the morphological features of ruffled borders. 4) Osteoblasts projected thin and long cell processes, which run in parallel orientation, suggesting that the processes involved in formation of collagen fibers running parallel in the bone marix. 5) Bones formed in osteosaroma showed adnormal and irregular orientation of fibers in bone matrix. 6) Bone esorption lacunae at giant cell tumor in bone were deep but similar to normal, suggesting that the lacunae were formed by activated osteoclasts.