Hair Structure

Hair grows from a follicle that is located below the surface of the skin. The skin of the scalp is exactly similar to the skin on any other body part. 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.

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.

Each hair is made up of three layers the cuticle or the outer most layer which has tiny over lapping transparent scales. When the scales lie flat against each other, the hair appears shiny, but when the scales are lifted, hair seems rough and dull. Conditioning rinses help to keep the scales positioned correctly, giving it a smooth and shiny appearance. Also oily hair is less porous than dry hair.

The porous nature of hair allows for the penetration of chemicals. The agents used in bleaches, tints and perms capitalise on this nature of the hair - the chemicals used are quickly absorbed and bring about the necessary changes in colour and curliness.

Hairs are elongated keratinized structures. The hair shaft, which is the only part we see, is composed mainly of keratin and is entirely dead. In the papilla, cells multiply and produce a protein called keratin - this is responsible for the hardness of the hair.

If the hair is coloured it is due to the presence of pigments- either melanin (black or brown) or pheomelanin (red or yellow). If these pigments are lacking the hair is white. Canites is the term given to grey hair, it is an illusion created by the mixture of white and coloured hairs. Actual individual "grey" hairs do not really exist. Hair grows from a follicle.

The lower part of the follicle widens out to form the hair bulb that contains the germinal matrix, the source of hair growth. Dermal tissue projects into the follicle base to form the dermal papilla, and this has a network of capillary blood vessels to supply oxygen, energy and the amino acids needed for growth.

In the follicle the hair is surrounded by an inner root sheath that has three layers. Henles layer is one cell thick and lies to the outer root sheath. 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.