A human hair consists mainly of a soluble protein called keratin. It also contains an amount of moisture and the trace metals and minerals found in the rest of our body.
The visible part of the hair, referred to as the shaft, is composed of dead tissue: the only living part of the hair is its root, the dermal papilla, which lies snugly below the surface of the scalp in a tube-like depression generally referred to as the follicle. The dermal papilla is made up of cells that are fed by the bloodstream.
The Structure Of Hair
Each hair consists of three layers. The outer layer, or cuticle, is the hair’s protective shield and has tiny overlapping scales, rather like tiles on a property roof. When the cuticle scales lie flat and neatly overlap, the hair feels silky-soft and looks glossy. If, however, the cuticle scales have been physically or chemically damaged or broken the hair will be dull and oftentimes brittle and will almost always tangle easily.
Under the cuticle lies the cortex, which is made up of fibre-like cells that provide the hair with strength and elasticity. The cortex also contains the pigment known as melanin, which provides the hair with natural color. At the center of each hair is the medulla, consisting of very soft keratin cells interspersed with spaces. The actual function of the medulla is not known, but some authorities believe that it carries nutrients and other substances to the cortex and cuticle. This could explain why hair is affected so rapidly by change in health.
Hair’s natural shine is supplied by its own conditioner, sebum, an oil composed of waxes and fats and also containing a natural antiseptic that helps the hair fight infection. Sebum is produced by the sebaceous glands present in the dermis. The glands are linked to the hair follicles and release sebum into them. As a lubricant sebum provides an excellent protective coating to the entire hair shaft, smoothing the cuticle scales and helping hair retain its natural moisture and elasticity. The smoother the surface of the cuticle, the lighter will be reflected from the hair, and therefore the higher will be the gloss. This is why it is more difficult to obtain a sheen on curly hair than on straight hair.
Under some circumstances, for example excessive hormonal activity, the sebaceous glands produce too much sebum, and the result is greasy hair. Conversely, if too little sebum is produced the hair will be dry.
FACT FILE
 HAIR GROWS ABOUT 12MM / 1/2" PER MONTH. |
| A SINGLE STRAND LIVES FOR UP TO 7 YEARS. |
| IF A PERSON NEVER HAD THEIR HAIR CUT IT WOULD GROW TO A LENGTH OF ABOUT 42" BEFORE FALLING OUT. |
| WOMEN HAVE MORE HAIR THAN MEN. |
| HAIR GROWS FASTER IN THE SUMMER AND DURING SLEEP. |
| HAIR GROWS FASTER BETWEEN THE AGES OF SIXTEEN AND TWENTY FOUR. |
| BETWEEN THE AGES OF 40 AND 50 WOMEN TEND TO LOSE ABOUT 20 PERCENT OF THEIR HAIR. |
| HAIR BECOMES DRIER WITH AGE. |
The Unique Growth Cycle
The only living part of the hair is underneath the scalp when the hair has grown through the scalp it is dead tissue. Hair goes through three stages of growth: the anagen phase when it actively grows; the catagen, or transitional phase when the hair stops growing but cellular activity continues in the papilla; and the telogen, or resting phase, when
growth stops completely. During the telogen phase there is no further growth or activity at the papilla; eventually the old hair is pushed out by the new growth and the cycle begins all over again. The anagen phase continues for a period of two to four years, the catagen phase for only about fifteen to twenty days, and the telogen phase between ninety to one hundred and twenty days. At any given time, about ninety three percent of a individual’s hair is in the anagen phase, one percent is in the telogen phase. Scalp hair, which reacts to hormonal stimuli just like the hair on the rest of the body, is genetically programmed to repeat its growth cycle twenty four or twenty five times during an average person’s lifetime.
growth stops completely. During the telogen phase there is no further growth or activity at the papilla; eventually the old hair is pushed out by the new growth and the cycle begins all over again. The anagen phase continues for a period of two to four years, the catagen phase for only about fifteen to twenty days, and the telogen phase between ninety to one hundred and twenty days. At any given time, about ninety three percent of a individual’s hair is in the anagen phase, one percent is in the telogen phase. Scalp hair, which reacts to hormonal stimuli just like the hair on the rest of the body, is genetically programmed to repeat its growth cycle twenty four or twenty five times during an average person’s lifetime.
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