Hair Structure

Hair grows from a follicle that is located below the surface of the skin. The part of the hair we see above is dead, the actual living part is very small which is knows as root of the hair which exists in the part known as the papilla. In the papilla, cells multiply and produce a protein called keratin - this is responsible for the hardness of the hair. The part of the hair which is within the skin, is enclosed by a sleeve of tissue called the follicle. Next to each follicle is a sebaceous gland, the oil producing factory of the skin. This oilforms a natural protective film over the length of hair, keeping it soft, shiny and supple. Each hair has a spong inner core, the medulla, which is surrounded by a stronger layer called the cortex. The cortex is reponsible for the strength, thickness, and flexibility of the hair. It also contains melanin, the pigment that determine hair colour. Any product designed to bring about permanent change, such as bleaches, tints and perms, must penetrate the cortex to restructure a hair's characterstics. The cortex is protected by the cuticle, which is a transparent layer of tiny, overlapping scales of keratin. When the hair is in good condition the keratin scales will be shiny and lie flat; if your hair is tangled, dry or damaged the scales will be ruffled, which will give your hair a dull appearance and a rough texture.

The hair root is the portion of the hair structure located beneath the skin surface and enclosed within the hair follicle. If the hair is coloured it is due to the presence of pigments- either melanin (black or brown) or pheomelanin (red or yellow). Hair is composed primarily of proteins (88%). Keratin protein is comprised of what we call "polypeptide chains." The word, polypeptide, comes from the Greek word "poly" meaning many and "peptos" meaning digested or broken down. Many (poly) amino acids joined together form a "polypeptide chain". Two amino acids are joined together by a "peptide bond", and the correct number of amino acids placed in their correct order will form a specific protein; i.e. keratin, insulin, collagen and so on. The "alpha helix" is the descriptive term given to the polypeptide chain that forms the keratin protein found in human hair. Its structure is a coiled coil. Melanocytes are present in the upper part of the papilla, producing pigment granules that are distributed throughout the cortex. Huxley's layer is two or three cells thick and is in the middle of the sheath. The cuticle of this inner root sheath interlocks with the cuticle of the hair. Both the hair and the inner root sheath grow at the same rate, but the inner root sheath breaks down about two-thirds of the way up the follicle, so only the hair emerges past the skin surface. Uncut hairs have a pointed tip.