Hair Growth and Lifecycle
HOW HAIR GROWS:
The normal development of hair is a continuously repeating cycle of growth, shedding and regrowth. The portion of the hair that we can see is called the shaft. Each shaft of hair protrudes from its follicle, which is a tube-like pouch just below the surface of the skin. The hair is attached to the base of the follicle by the hair root, which is where the hair actually grows and where it is nourished by blood capillaries.
Like the rest of the body, hair is made of cells. New cells form at its root, and the hair is gradually pushed further and further out of the follicle. The cells at the base of each hair are close to the blood capillaries, and are living. As they get pushed further away from the base of the follicle, they no longer have any nourishment, so they die. When they die, they are transformed into a hard protein called keratin, which is also the material of which fingernails and toenails are made.
So, each hair we see above the skin is dead protein. It is the follicle, which lies deep in the skin that is the essential living and growing part of hair.
Hair growth follows a specific growth cycle with three distinct and concurrent or simultaneous phases or stages. Since this occurs all at the same time, three strands of hair in the same area of the head may be found in each different phase. Each phase has specific characteristics that determine the length of the hair:
Anagen Phase: This is the growing stage where the hair grows at about a ½ inch each month, and this phase usually lasts between 2 and 8 years .
Catagen Phase: As this phase begins, the base of the root or the bulb detaches from the bloody supply and the hair shaft is pushed up. This phase lasts 2 - 4 weeks.
Telogen Phase: This is the resting stage, during which there is no hair growth. This phase lasts up to 5 months and when it is over, the strand of hair is shed and a new strand begins growing to take its place in a healthy follicle.
At the end of the resting phase, the hair is shed, and the follicle starts to grow a new one.
At any moment, about 85% to 90% of the hair follicles of the scalp are growing hair in the first phase; only about 10% to 15% are in the resting phase.
If a follicle is destroyed for any reason, no new hair will grow from it.
Hair regrowth from miniaturized follicles can occur once microcirculation-- the system of blood vessels and capillaries surrounding the root of the hair that nourish it -- to the follicle is improved and follows the same cycle outlined above.
