Morphological alteration of human hair with aging

Abstract

Human hair gradually develops from birth until adolescence and subsequently shows morphological alteration by aging although there are man and woman difference and individual difference. In this article, firstly I explain about the structure and function of hair apparatus, the mechanism of hair cycle, and the expression of hair color.
As pilar aging phenomena, senile alopecia, senile hypertrichosis and canities are described. Senile alopecia is known to be the same as male pattern baldness, and thinning and shortening of vertex-forehead hair occur and androgen and hair papilla cells play important roles in miniaturization of hair apparatus. On the other hand, with men in particular, the eyebrows, beard, tragi and nostril hair become hypertrichosis with aging adversely. White hair color in canities is due to dysfunction and/or disappearance of hair matrix melanocytes; this may be caused by a problem of differentiation/proliferation of melanocyte-stem cells. (Online only)