In order to execute its functions of protection, insulation, sensation, cleansing, and
communication, the hair follicle must undergo complex, tightly controlled processes of
growth and differentiation. Four major processes of control are recognized in the biology of
hair. First, heterogeneity ofform: Follicles produce hair with widely different features at
different sites. Follicles and their resultant hair shafts differ in their length, texture, curvature,
curl, androgen sensitivity, and color; in fact, except for bilateral symmetry, probably no two …