[Physiology and bone physiopathology].

The bone tissue is one of the largest of the organism, with clear functions: to serve as a support and protection for the soft parts, as support for movement with the anchorage of the muscles, as mineral reserve and as interactive storage of the bone marrow. To exercise all these functions the bone must maintain its quality, a concept that combines its degree of mineralisation, its microarchitecture and its capacity to repair lesions, aspects that are included in the broad definition of osteoporosis: "A systemic disease of the skeleton, characterised by a low bone mass and a deterioration of the microarchitecture of the bone tissue, which jointly result in an increase in bone fragility and the consequent increase of the risk of fractures", although from the clinical point of view we have to centre our attention on mineralisation, a quantifiable aspect, understanding as osteoporosis a fall in bone mass greater than 2.5 standard deviations below that of young healthy patients. This article reviews the physiopathological aspects that influence the development of this frequent clinical picture.