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Home > Hair Physiology > Hair Growth Cycles
It takes a long period of two to six years for every hair strand on the scalp to attain its ultimate growth potential. During this lengthy growth period the hair is washed, conditioned, exposed to the heat and pollution, chemically treated etc. None of these factors affect the normal growth of the hair follicles, but they can damage the hair shaft. Hair follicles in the skin remain unaffected by the harmful effects of the environment and continue with their normal cyclical process of hair growth and renewed re-growth after resting for a small period.
The phases of hair growth cycles
The cyclical process of hair growth can be divided into three major phases
There is another phase called as Exogen which mainly concerns with the shedding of the hair, but it also seems to affect the anagen phase.
The time duration of the particular hair growing phase depends on the age of the individual, the intake quantity of natural supplements, hormone levels, and other physiologic and pathologic factors.
Anagen phase in hair re-growth
The anagen phase is considered to be the longest period when compared to the other phases of hair growth cycles. The anagen phase of scalp hair follicles lasts for about 2-6 years and 90% of the hair follicles in a normal human scalp remain in this active hair growth phase at any given point of time. The duration of the anagen phase determines the ultimate length of the hair. During the anagen phase, a hair strand grows about 1 cm in every 28 days.
The anagen or growing stage involves the complete re-growth or regeneration of the lower, cycling portion of the follicle. The epidermal cells surrounding the dermal papilla form the germinal matrix or root of the hair. These cells are constantly dividing, leading to the formation of new cells. These new cells push the older ones upwards resulting in hair growth.
Catagen phase in the hair growth cycles
Major destruction (apoptosis) at the lower end of the follicle indicates the onset of catagen phase in the cyclical process. As soon as the anagen phase is complete, the normal process of growth in the hair follicles stops and degeneration begins.
In the catagen phase there is a withdrawal of papilla cell fibroblast projections from the basement membrane. The papilla shrinks, probably due to the loss of extra-cellular matrix substance. At the end of the catagen stage, dermal papilla moves upward through the skin, and comes to rest beneath the hair-follicle bulge.
At the same time matrix and lower outer root sheath abruptly stop multiplying and the melanocyte cells also stop the production of melanin pigment. There is a normal cell death in most of the keratinocyte and melanocyte cells.
Telogen period in hair growth cycles
Telogen is the resting stage in the normal cyclical process of hair re-growth. After the normal degeneration and decline of growth in the catagen phase, a ‘club hair’ is formed in the telogen phase before it is finally shed out.
A club hair is formed by accumulating the last hair growth cells at the end of the hair fiber. These lumps of cells clubbed together actually hold the hair fiber in the tube of hair follicle. The hair in telogen phase is called a ‘club hair’ as the lump of cells at the end of the hair fiber gives it a club like appearance.
Though the dead hair is attached in the scalp by the club of cells, it can be easily pulled out by normal washing, combing, etc.
Exogen is the last phase of hair growth cycles
Exogen, or hair shedding, is the last phase of all hair growth cycles. On any given day, every human being looses about 50-150 hairs due to the exogen phase.
Exogen deals mainly with the hair shaft base and not directly with the hair follicles. The details of the exogen mechanism are poorly understood, but it certainly influences the anagen phase.
It is necessary to understand the normal cyclical process of hair re-growth which in turn will help you to understand the hair loss causes.
Normally, the cyclical process of hair growth and inactivity goes on for the over all lifespan of the individual. But some factors like harmful medications or radiation, hormones, and genetics can disturb this normal cyclical process leading to severe hair loss.
By taking good care of your hair, with proper nutrition and natural hair care products you can help your hair to be in good health.
Understand the natural cycles of hair growth and take care to maintain their structure and function without harming them.