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Hair Growth Cycle

Each hair shaft grows out of a hair follicle located in the epidermis, the outermost layer of skin on the scalp. The scalp consists of a great number of individual hair follicles, each working independently. Deep within the hair follicle two substances are generated: a protein named Keratin of which the hair is formed, and a Pigment called Melanin which dictates the colour of the hair. The quality of the growing hair is dependent on the amount of keratin generated within the hair follicle. A sufficient quantity will generate thick, strong hair. Lack of keratin will result in weaker and thinner hair.

The growth cycle of the hair consists of 3 phases:

1. Anagen - The growth phase: during this phase, keratin is generated at the base of the hair follicle and forms the hair shaft. It lasts about 5 years, and 90% of all hair follicles are in this phase at any given time. The exact length of this period varies from one person to another depending on several factors such as age, race, health etc.
2. Catagen - The resting phase: The hair shaft stops growing and its root shrinks. It begins to slide out of the shrinking hair follicle, moving further away from the blood vessels supplying it with the amino acids, vitamins and minerals needed for the generation of the keratin and melanin. With time, the hair shaft will just fall out of the follicle. This phase lasts for anywhere between a few days to two weeks. Only a few percents of the follicles are in this phase at a time.

3. Telogen - The regrowth phase: The hair follicle returns to its normal state and the formation of a new hair shaft begins. If by this time the pervious hair shaft did not slide out of the hair follicle, it will be gradually pushed out by the new growing hair shaft. The duration of this period is a few months.

Losing fifty to a hundred hairs a day is considered normal.

Hair Growth Cycle: The Anagen Phase
Anagen
Hair Growth Cycle: The Catagen Phase
Catagen
Hair Growth Cycle: The Telegon Phase
Telogen
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