HAIR STRUCTURE  

People often see the hair as a only a hair but they don’t consider what is a hair. A hair is a specialized outgrowth of part of part of the skin called the epidermis. It has two distinct parts: the hair follicle and the hair shaft. It also comprises of three layers called the medulla, an inner core, an outer layer called the cuticle and a layer in between called the cortex.

The Hair Follicle              

A hair follicle is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is the point from which the hair grows. It is well supplied with minute blood vessels, and the blood passes through them nourishes the growing region. The temperature, and is not affected by cold or hot weather. Human hair grows at different rates depending on the amount of natural light, which varies according to the time of the year: it grows a little bit faster the winter than in summer.A hair follicle is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is the point from which the hair grows.

    A hair follicle is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is the point from which the hair grows. It is well supplied with minute blood vessels, and the blood passes through them nourishes the growing region. The temperature, and is not affected by cold or hot weather. Human hair grows at different rates depending on the amount of natural light, which varies according to the time of the year: it grows a little bit faster the winter than in summer.

The hair follicle van be divided into two regions:              

The hair bulb                                                 

The hair bulb lies inside the hair follicle. It is a structure of actively growing cells, which eventually produce the long fine cylinder of hair. New cells are continuously produced in the lower part of the bulb. As they grow and develop, they steadily push the previously formed cells upwards. When the cells reach the upper part of the bulb, they begin to change and the arrange themselves into six cylindrical layers, one inside the other. The inner three layers of cells become the actual hair. The outer three layers become the lining of the hair follicle – the inner root sheath.Special cells in the hair bulb produce a pigment that colours the hair. The pigment is called the melanin, and these cells are known as melanocytes. As the developing hair moves upwards in the follicle, the melanin is carried upward in the inner part of the hair.

 

The mid-follicle region

    In this part of the follicle, the actively growing cells die and harden into a hair. As the cells below continues to divide and push upwards, the hair grows upwards too, out of the skin. It now consists of a mixture of the special hair protein, keratin.

    Some of these keratins contain a high level of sulphur. The sulphur plays an important part in the way the hair behaves, especially when it is given cosmetic treatments.

This is the part of the hair that can be seen above the scalp. It consists mainly of dead cells that have turn into keratins and binding material, together with small amounts of water.

Terminal hairs on the head are lubricated with natural oil (sebum) produced by the sebaceous glands of the follicles. How much natural oil your glands produce is mostly determined by your genetic inheritance. But in addition, boys’ and girls’ glands tend to produce more oil when levels of their hormones (androgens) are high. In many teenagers, a massive surge in hormone results in the tendency to greasy hair.

Structure of the hair shaft           

The centre part of the hair, called the cortex, makes up most of the hair shaft. It is the cortex that gives hair its special qualities such as elasticity and curl. The cortex is packed with strands of keratin, lying along the length of the hair. These keratin fibres are made of the low-sulphur keratins, and are compressed into bundles of larger fibres. These are held together by a mass of sulphur-rich keratins, the matrix. The fibre-matrix combination is extremely strong and resists stretching and other strains such as twisting.

   

    The cortex also contains granules of the hair pigment melanin, produced when the hair is growing in its follicle. The granules are of two types: smooth, dark granules which tend to be regularly positioned within the cortex, and lighter granules that are more irregular in shape and is scattered randomly through the cortex. A hair may contain just one type of granule or a mixture.

    In some of the terminal hairs, the cortex has a central hollow core, the medulla. The outer layer of the hair is called the cuticle. It is made up of between six and ten overlapping layers of long cells. Each of these cells or scales is about 0.3 micrometres thick and around 100 micrometres long, and about 10 micrometres across. The scales lie along the surface of the hair like tiles on a roof, with their free edges directed towards the tip. They cover the hair surface all the way along its edges.

    Black hair reflects less light than blond hair does. Black hair appears glossier because the bright bands of reflected light contrast more sharply with the darkness of the rest of the hair.