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Scanning electron micrograph (SEM) of human head hair, showing details of a normal shaft. Hair is a fibrous protein (keratin), which develops out of a tubular hair follicle located in the epidermis of the skin. The shaft, the part visible above the skin, consists of three layers; the outer layer or cuticle, which is scaly, the cortex, containing hair colour pigments and the medulla, the central core, sometimes hollow. The hair shaft is made up of dead cells. Growth is due to a layer of dividing cells at the base of the root. As new ones are formed, older ones are pushed upward and keratinized. Mag: X 3800.
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