People today no longer make use of hair for protection, heat retention or camouflage. But still hair is a very important means by which they display and are recognized, especially with today's increasing life expectation.
Hair is an integral part of the structure of our skin & plays an important role with the skin in our overall physical appearance & self perception.

What is hair? and how does it grow?

Hair is basically a form of skin. It is made up of a protein called keratin and grows everywhere on the body with the exception of the lips and eyelids and the palms of the hands and soles of the feet.
Hair grows from follicles within the skin. The part of the hair inside the follicle (below the skin's surface) is known as the hair root, while the portion you see protruding from the head is the hair shaft. At the base of the hair root is the hair bulb where nutrients are received and new cells are formed.
Also within the hair follicle are the dermal papilla (a cone shaped protrusion at the base of the follicle which feeds blood - and therefore nutrients - to the hair bulb).
Taking nutrients from the dermal papilla, the hair bulb generates new hair cells. As these cells move up through the hair root, they mature through a process called keratinization, fill with fibrous protein and lose their nucleus. When the cell loses its nucleus it is no longer alive. By the time the hair emerges from the skin it is merely fiber made of keratinized proteins.
The fibrous protein emerging from the hair follicle as the hair shaft has a specific construction. It forms a strand with three layers: an outer covering of overlapping keratin scales called the cuticle (for protection), a middle layer of keratinized protein fibers called the cortex ( contains the natural pigment melanin), and, usually, a central 'core' of round cells called the medulla.

Normal hair growth cycle :

Human hair grows in a continuous cyclic pattern of growth and rest known as the "hair growth cycle". Three phases of the cycle exist: Anagen= active growth phase; Catagen=degradation (transition) phase; Telogen= resting phase. Periods of growth (anagen) between two and six years are followed by a brief period, in which the follicle is almost totally degraded (catagen). The resting phase (telogen) then begins and lasts five to six weeks. Shedding of the hair occurs only after the next growth cycle (anagen) begins and a new hair shaft begins to emerge.

What Is Hair Loss?

Most people routinely lose between 70 and 150 hairs from their scalp each day, mainly through washing, brushing, and combing.
Scalp hair starts to thin when more hairs are lost through normal shedding than the scalp is able to renew. About 40% of the density of scalp hair has to be lost before thinning of the hair becomes noticeable.

What causes hair loss?

There are many causes of hair loss in men and women, including disease, nutritional deficiency, hormone imbalance, and stress. However, by far the most common cause is what is called androgenetic alopecia. Alopecia is simply the medical term for hair loss. Androgenetic refers to the fact that both a genetic predisposition to balding, and the influence of androgens, or male hormones, play a part in this type of hair loss.
In fact, there is a third factor, which is the passage of time, or aging. In other words, in order for androgenetic alopecia to occur, there must be:

* A genetic propensity for balding .
* The presence of androgens, or male hormones.
* Enough aging time to allow the first two factors to exert their influence on the hair follicles.

All normal men and women produce "male" hormones. The most common of these are testosterone, androsteinedione, and dihydrotestosterone (DHT). These hormones are quite important in both sexes, but occur in different concentrations, being much more predominant in males than in females. This, in part, is responsible for the typical differences between the genders.

Mechanism of hair loss :

In certain cells of the hair follicle, and in the sebaceous glands, there are high levels of an enzyme called 5-alpha-reductase. What this enzyme does is to convert testosterone, which is delivered to these areas by the blood, into DHT. This exposure of the hair follicles to DHT, in a genetically susceptible person, over a period of time, leads to androgenetic alopecia, or male and female pattern baldness.
There is no set age at which balding occurs. Like any process, it can be rapid or slow, it can begin toward the end of life or in the late teens.

What happens to the hair?

As the follicles are continuously exposed to DHT, an interesting phenomenon occurs. The anagen phase (active growth phase) of the hair becomes gradually briefer and briefer, and eventually the hair becomes finer and shorter, and less deeply colored. We call this "miniaturization" of hairs. This is also the point at which hair loss tends to first be noticed. It’s not that there are fewer hairs on the head, but that their caliber (cross-sectional area), color and length are so diminished that they no longer provide "coverage" for the scalp beneath. Light penetrates through to the shiny scalp, and this is perceived by the observer as "thinning" or balding.
Also, an increased number of hairs are in the telogen phase. The telogen hairs are easily dislodged during washing, drying, or combing, and this is the second sign of balding: in addition to the apparent thinning seen with miniaturization, we begin to see larger numbers of hairs on the comb, the towel, the pillowcase, or in the bathroom drain. This can be quite traumatic, especially for the younger man or for women.