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Hair Structure, Healthy Hair Facts and StructureGiven that healthy hair is a reflection of one's general health, it is ironic that the visible part of a hair - the hair shaft - is physiologically speaking, dead, with only the tiny part underneath the scalp (the root or dermal papilla) consisting of living hair- forming cells known as trichocytes and keratinocytes. The dermal papilla, nourished by a network of blood vessels and nerves, is nestled in a tube like hair follicle and surrounded by what is known as the bulb. The bulb is embedded about 4mm (0.2in) in the subcutaneous fat of the scalp. The outer layers of the hair bulb are known as the outer and inner root sheaths. It is in the dermal papilla that most hair growth takes place. In order for hair to grow, cells have to reproduce. This takes place around the dermal papilla in what scientists call the zone of proliferation. Each hair has a protective outer cuticle, made up of tiny overlapping scales, often compared to miniature roof tiles, and a thick cortex that lies under the cuticle and consists of the protein keratin. Keratin is also found in human skin and nails, as well as in the feathers, claws, hooves and wool of birds and animals. Hair also contains the elements carbon, oxygen, nitrogen and sulphur and a tiny percentage of the trace elements zinc, iron, copper and iodine. Other components include fats, and water, which makes up about 12 per cent of a hair's weight. Some type of hair - particularily thick, dark hair - also have a central medulla, which when inspected under an optical microscope, looks a little like a central canal. Some scientists believe it enhances the thermal-insulation properties of hair. Others speculate that the medulla carries nutrients to the cuticle and cortex, while yet another theory is that it contributes to the shine of hair. Hair Structure Parts
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