Human Hair Keratin Network And Curvature
October 2007
in “
International Journal of Dermatology
”
hair curl patterns cross-sectional rotations macrofibril organization curly hair follicles retrocuvature proliferative compartment inner root sheaths outer root sheaths elliptical hair cortex asymmetric hair cortex hHa8 keratin concave side hair shaft asymmetric differentiation precortex shape memory material
TLDR Curly hair shape is due to uneven growth patterns in the hair follicle.
The study investigated the structural elements related to hair curl patterns by examining human hair samples ranging from straight to tightly curled. It found that the frequency and amplitude of cross-sectional rotations were crucial for describing curliness at the macroscopic level. Transmission electron microscopy revealed that macrofibril organization was strongly related to hair curliness, with curly hair follicles exhibiting retrocurvature regardless of ethnic origin. The study highlighted an intrinsic asymmetry in the proliferative compartment of curly hair, causing delayed differentiation of inner and outer root sheaths and resulting in an elliptical and asymmetric hair cortex. The accumulation of hHa8 keratin on the concave side of curly hair, as opposed to the even distribution in straight hair, suggested that the curly shape of the hair shaft resulted from asymmetric differentiation of the precortex, making hair fiber a shape memory material.
