haarschacht

Haarschacht, Dutch for hair shaft, denotes the portion of a hair that extends from the hair follicle to the tip and is visible above the skin. The shaft consists of keratinized, dead cells and is neither vascularized nor innervated; living tissue resides in the hair follicle below the surface.

Structure: The shaft has three layers: cuticle (outer, overlapping cells protecting inner layers), cortex (bulk, keratin fibers and pigment), and medulla (central core, present in thicker hairs and absent in fine hair).

Development and growth: The shaft is produced by hair follicle matrix cells that keratinize as they move upward. Keratinized cells form the dead shaft. Hair cycles through anagen (growth), catagen (transitional), and telogen (rest). The length of the anagen phase determines potential shaft length.

Function and properties: The shaft provides protection and insulation. Color comes from melanin in the cortex; strength and elasticity depend on cortex structure and cuticle integrity.

Care and disorders: Cuticle damage from heat, chemical treatments, or UV exposure roughens the surface and leads to breakage and split ends. Disorders of the shaft are rare and usually affect texture or strength rather than color or growth.