1Department of Anthropology, Western University, London Ontario, Canada, 2Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Canada
March 27, 2015 , Archview Ballroom
Understanding bone histomorphometry has been useful in anthropology for estimating age and physical activity, identifying species and disease, and tracking taphonomy and diagenesis. This is true despite considerable variability in regional microstructure across development and between sexes. For example, histologists have long recognized that small secondary osteons can appear within the boundaries of a previously existing osteon. Evidenced by an internal reversal line, these ‘Type II’ osteons have been attributed most often to maintenance of mineral homeostasis and seem to increase in frequency with age. However, current 3D histological techniques reveal Haversian systems are more complex networks than previously realized. In addition, careful observation of 2D fragment orientation indicates generations worth of fragments have associations with the most recent osteons. This suggests existing osteonal vessel systems can simply be reused. This type of repathing activation begins along a vessel canal rather than branching off from it and can remain internal with respect to the original system’s cement line (creating a type II osteon). Alternately it can resorb past that cement line in one or more directions to turn over adjacent primary or secondary tissues without the need for metabolically expensive angiogenesis and without resulting in the generation of new canals, a previously undescribed phenomenon. Combined 2D and 3D perspectives like this one shift the attention from remodelled bone to its dynamic vascular system and result in new testable hypotheses. Implications for histological age estimation and the study of osteopaenia also warrant future attention.