DAVID SCHARF / SCIENCE PHOTO LIBRARY. DAVID SCHARF / SCIENCE PHOTO LIBRARY.
Scanning electron micrograph (SEM) of a shaft of badly damaged human head hair. Hair is a protein (keratin), which develops out of a tubular hair follice found in the skin epidermis. The shaft, the visible part, consists of three layers; an outer scaly layer, the cuticle, which is mostly lost in this damaged specimen; a middle layer, the cortex (largely what's visible here), forming the bulk & containing hair colour pigments; & a central core, the medulla, which may be hollow. Hair cells are dead except for a layer at the base of the root which divide to form new cells, pushing the older ones upward & finally beyond the skin surface. Mag: X1,000 (10x8).
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