Dog hair. Coloured Scanning Electron Micrograph (SEM) of the shafts of dog hairs. Each hair shaft has an outer cuticle of flat over-lapping scales or plates, as seen here, which it is thought, prevent the hairs from matting together. Hair is made up of a fibrous protein called keratin. Internally the hair shaft is divided into three concentric sheaths (layers) called the medulla, cortex and outer cuticle. It consists of non- living tissue. Hair growth occurs when epidermal cells divide within the root bulb, and as they are pushed out of the hair follicle they become increasingly keratinised to form tough scales. Magnification: x550 at 5x7cm size.
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