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Age Changes in the Organic Fraction of Bone

By J. W. Smith and St Andrews


Mammalian bone is a heterogeneous tissue which is divisible at the microscopic level into units or regions of different appearance. The relationship of these units to one another is, in large measure, a reflection of the developmental processes by which the tissue has been formed. Primary bone is laid down either as surface bone (concentric lamellar bone) or as primary osteones, but in many species this is not a permanent tissue. As it ages it undergoes focal resorption and, in the vascular spaces so created, secondary osteones are formed by the centripetal accretion of new bone. Subsequently these secondary osteones are themselves partially resorbed and replaced by new osteones of similar form. Once established, this process of internal resorption and replacement continues throughout life, and the extent of its effects on bone architecture is related to the life span of the species concerned. The bone which surrounds secondary osteones is often described collectively as the interstitial tissue, and its structure exhibits both species and age variations. During the period of growth, and for some time after in many bones, it consists, largely or entirely, of primary bone, either in the form of primary osteones (Figs. 1 and 2) or as surface bone (Fig. 4). However, as age advances the remnants of partially resorbed secondary osteones progressively replace the primar

Year: 1963
DOI identifier: 10.1302/0301-620x.45b4.761
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