Science of Hair
Facts About Hair
Humans, in average are covered with hair all over their bodies, with the exception of the palms of the hands, soles of the feet and the lips. Hair is noticeably more obvious on the scalp and face while including the nose and ears in certain cases, the armpits, the groin and the chest and legs.
Facts About Hair Follicle
The hair follicle is the physical point from which the hair starts to grow and is a tiny cup-shaped pit buried deep in the fat of the scalp. The hair follicle is well equipped with blood vessels, and the circulation of blood through them causes the nourishment of the growing region the surrounding temperature of the hair follicle is approximately the same as normal body temperature and it remains unaffected by hot or cold water.
Hair growth of animals for instance grows at varying rates depending on the amount of exposure to natural light, which accordingly changes depending on the time of the year; it grows faster in the winter when the days are short. It is assumed that the behavior of human hair in very similar, growing a little faster in the winter. The hair follicles consists of two divided regions; the hair bulb and the hair shaft.
How much hair do humans have?
• On average, each person's head carries about 100,000 hair follicles. Some people have as many as 150,000 or even more.
• On a baby's head, there are about 1,100 follicles per cm square.
• By the age of 25, this number has fallen to about 600, but the number depends on the physical type of the individual.
• Between the ages of 30 and 50, the number drops further, to 250-300. After this point there is only a slight further fall with age.
• Each follicle grows about 20 new hairs in a lifetime. Each new hair grows for several years, and can reach over 1 meter in length.
• Each hair falls out eventually, and is replaced by a new one.
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 a hair.
New cells are produced at a continuous rate 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 they form themselves similar to six cylindrical layers, each one inside the other. Consequentially, 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.
The pigment that colors the hair are produced by special cells in the hair. The pigment is called melanin and the cells are known as melanocytes. As the developing hair moves upwards in the follicle, the melanin is carried upwards in the inner part of the hair.
The Mid-Follicle Region
The mid-follicle region is where the actively growing cells die and harden into what we call a hair. As the cells below continue to divide and push upwards, the hair grows upwards, eventually out of the skin. It now consists of a mixture of different forms of the special hair protein, keratin.
Some of these keratins contain a high level of sulphur, some much less. The sulphur plays an important role in the way the hair behaves, especially when it is given cosmetic treatments.
What is the hair shaft?
This is the part of the hair that can be seen above the scalp. It consists primarily of dead cells that have turned into keratins and binding material, together with small amounts of water.
Terminal hairs on the head are lubricated by a natural oil (sebum) produced by the sebaceous glands of the follicles. The amount of natural oil your glands produce is mostly determined by your genetic inheritance. However, for men and women, glands tend to produce more oil when levels of their hormones (androgens) are high. In many teenagers, a massive surge in hormone levels leads to raised grease production. This results in a tendency to greasy hair, which many young people would be well familiarized with. The good news is that most of them outgrow it.
Structure of the hair shaft
Smooth, glossy hair possess a much more complicated structure than one might imagine. Each one is comparable to a tree: all its moisture lies in its center, behind a tough outer layer of protective bark. If the 'bark' of the hair is well maintained, the whole hair remains in good condition but if the 'bark' is stripped off to expose the centre the hair may break.
The center 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. It (cortex) is packed with strands of keratin, lying along the length of the hair. These keratin fibers are made of the low sulphur keratins, and are compressed into bundles of larger fibers. These are held together by a mass of sulphur rich keratins, the matrix. The fiber matrix combination is extremely strong and resists stretching and other strains such as twisting, much as does the glass fiber resin mixture from which many boats are built.