Hair Follicle Biology and Shaft Structure

Abstract

Background: Hair follicle biology and hair shaft structure are essential for maintaining normal hair integrity, growth, and resistance to external damage. The hair follicle is a complex mini-organ composed of distinct anatomical regions that regulate hair formation and cycling. The hair shaft itself consists of the cuticle, cortex, and medulla, each contributing specific structural and functional properties. Variations in hair composition and morphology occur among different ethnic groups and influence susceptibility to mechanical and chemical damage. Cosmetic procedures such as bleaching, coloring, and hair straightening can disrupt the protective cuticle layer, alter the biochemical composition of hair fibers, and impair hair strength and biomechanical properties. Understanding the anatomy, composition, and growth cycle of hair provides a scientific basis for recognizing the mechanisms of hair shaft damage and the effects of cosmetic interventions on hair health.