Bone thickness and brain growth

Anzelmo et al 2014Cranial vault consists of two cortical tables (inner and outer) sandwiching a layer of trabecular bone (diploe). Cranial vault thickness (CVT) is the distance between endocranial and ectocranial surfaces of vault bones. Several studies have pointed out that CVT differs not only between hominids but also among modern human populations. This morphological trait is mainly influenced by systemic and local stimuli, such as brain growth and development, mechanical forces (at the muscles attachments), circulating hormone levels, formation of sutures etc.  Marisol Anzelmo and colleagues have recently published a study of ontogenetic changes in CVT in a modern sample of Homo sapiens. They tested age differences in CVT and if these changes are associated with changes in endocranial volume (EV), which reflect brain size. CT cranial images of 143 individuals (males and females) from 0 to 31 years were used to obtain, among others, a thickness mean measure (TMM), a measure of endocranial volume (EV), and a 3D topographic mapping of CVT, which indicates thickness distribution at different regions through a chromatic scale. A topographic mapping is very useful for picturing differences across vault regions in every age group, and it also reveals development of the regions during ontogeny and the onset of adulthood. The results of this study show that TMM increases during ontogeny without sex differences. Most accelerated growth rates of TMM occur during the first 6 years of life. Also, association between TMM and EV was significant only in this period (infants and children). Furthermore, adult pattern of thickness distribution seems to begin early in ontogeny. Increase of CVT in early ontogeny is directly linked to brain protection. However several mechanisms are involved in CVT formation, such as sutures patterning and vessels development. The vault bones dynamic in later ontogeny and in adulthood may be then influenced by different type of muscular activity and mechanical demands or, most commonly, by systemic factors associated with hormones, physical activity, nutrition.

Stáňa Eisová


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