Layers of a Hair Strand

Description

Concentric layers of the human hair shaft (pilus) are rendered in cross-section, with the cuticle forming the thin, outermost ring of overlapping scale cells arranged like shingles around the circumference. Immediately deep to this, the cortex occupies the bulk of the strand, packed with elongated keratinized cortical cells and visible fibrous keratin bundles aligned along the long axis of the hair. Central to the shaft, a medulla is shown as a less dense core, acknowledging that it may be continuous, discontinuous, or absent depending on hair type and individual variation. Clear microanatomy. Dermatopathology and forensic work both hinge on these layers. Cuticle integrity and patterning help differentiate hair shaft disorders and identify weathering from heat, chemical processing, or traction, while cortical architecture explains changes in tensile strength and elasticity seen in trichorrhexis nodosa and related fragility syndromes. Medullary presence, diameter, and continuity provide teachable criteria used in basic hair microscopy and in species comparison, even when the follicle is not present in the specimen. Use this asset in integumentary system teaching (histology, dermatology, or cosmetic science) to anchor students on shaft versus follicle terminology, and to support figure panels in trichology reviews, dermatopathology atlases, and lab manuals covering light microscopy of hair. It also fits patient-facing education for alopecia clinics when discussing cosmetic damage versus intrinsic shaft defects. Anatomical accuracy verified by SciePro's Medical Advisory Board.