Physiological Factors Responsible for the Development of Osteopenia under Conditions of Mechanical Unloading

摘要: A summary of results investigations by the author and a brief review some literature data on human bone tissue deprived mechanical loading (spaceflight, hypokinesia) is given. The direction markedness changes in mass—the mineral density content—in different skeletal segments depend their position relative to gravity vector. theoretically expected mass reduction was revealed trabecular structures bones lower part skeleton (local osteopenia). In upper skeleton, an increase content observed, which considered as secondary response due redistribution body fluids cephalad. main cause osteopenia unloading. Arguments are presented that osteocyte osteolysis, delayed osteoblast histogenesis, osteoclast resorption provoked rearrangement hierarchy systems volume regulation, ion endocrine regulation calcium homeostasis mechanisms osteopenia.