Hair growth occurs as new hairs are formed at the base of the root follicle and molded by a structure, called the inner hair root sheath, that surrounds the growing hair shaft. Androgens, which is the male sex hormone, present in both men and women, activates specific body areas to produce hair growth. Hair growth occurs in cycles, or phases, and each follicles may be active or resting at any one time.
Growth rates vary greatly between different individuals and also the specific area of the body in question. Scalp hair, for example, grows at an average of one-tenth of an inch every week. Leg hair, however, is less active and only grows at about half that rate.
The repeating cycle of phases of growth and rest will affect the overall production of hair. There are no new hair follicles produced after birth – the appearance (and loss) of your hair is the result of the changing ratio in the growth/rest cycles.
The hair growth life cycle has three separate stages: anagen, catagen and telogen.
The cycle of each follicle begins with the anagen phase — the re-activating of the follicle’s growth where a new hair begins to lengthen. This active growth phase will continue for a period as short as several weeks (as found in the moustache) or even lasting as long as several years (like your scalp). Growth will continue for varying lengths of time, according to the area of the body, gender, hormones and other factors.
But eventually the level of growth begins to slow down. This next stage of slowing or arrested growth is known as the catagen phase. This slowing will continue into the third and ultimate phase – a period of complete inactivity or rest.
During the third so-called telogen stage, the hair has separated from its basal papilla and is no longer able to receive nourishment. At this point, no more new hair is being produced and the inactive hair only remains in place mechanically, and can be fairly easily shed by brushing, combing or other tension placed upon it. A short hair shaft remaining in place at the end of its growth cycle is called a club hair. It is not uncommon for such a club hair to remain in place while a newly formed anagen hair is beginning to emerge, forcing the club hair to be emerge and finally be shed.
Eventually the hair follicle will once again become active and begin to grow a new anagen hair. This repeated process of growth and inactivity will continue throughout your life. In man, follicle activity is generally spread across all stages of the hair life cycle, while other mammals can have a more orderly growth pattern, with noticeable periods of hair growth and subsequent shedding.
Do you know that just because your hair follicles get into the dormant stage, they can actually still be regrown if you take the proper steps? It’s true, even though some of your may have stopped growing, you can still regrow it.
Hair loss research center. M.Gardson