Hair Structure

Hair is all protein: The part of the hair we see is dead; the actual living part is very small and is at the root in a part known as the papilla. In the papilla, cells multiply and produce a protein called hard 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 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.

The cuticle of the hair is selectively porous. This porosity varies along the length of the hair, the youngest bit near the scalp being the least porous. 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.

Hair is composed of strong structural protein called keratin. This is the same kind of protein that makes up the nails and the outer layer of skin. Like other proteins in the body, keratin is also a large molecule made up of smaller units called amino acids. The amino acids are joined together in a chain, like beads on a string. Hair grows from a follicle. The walls of the follicle form the outer root sheath of the hair. The lower part of the follicle widens out to form the hair bulb that contains the germinal matrix, the source of hair growth. Melanocytes are present in the upper part of the papilla, producing pigment granules that are distributed throughout the cortex. 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.

A blonde head of hair has usually much more fibers than red or dark haired heads. Hair consists mainly of keratin, which is also responsible for the elasticity of fingernails. Hair growth is faster in summer than in winter. The growth of hair is cyclical, i.e., after a few years of growth, the hair enters a phase of inactivity, then dies and falls. The hair growth is rapid between the age group of 15 and 30, but declines drastically between the ages 50 and 60. Scalp hair grows faster in women than in men. A certain amount of hair is shed daily. The average amount of 50 to 80 hairs shedding daily is normal. The number of hair on the head vary with the colour of the hair, whether it is fair, brown or black, depends on natural pigment on its cortical cells-melanin. Melanin is produced in the pigment cells of the bulb and then passed into the cells of the cortex.