Hair Growth Cycle

The primary role of hair is for insulation by trapping warm heat against the body. Nowadays hair is more for social interaction rather than a survival mechanism. The cycle of hair growth can be broken down into 3 parts. The Anagen Phase, the Catagen Phase and the Telogen Phase.

Stage 1: Anagen Phase(growth phase)

In this stage, the hair bulb keeps on producing, and the strand continues to grow. This phase is the longest among all 3, and can sometimes last for a 1000 days. Hair usually grows about 1 cm per month, so this phase continues until the hair grows to a meter or more. The older you are, the shorter this phase becomes, and hair becomes thinner.

Since this stage is so long in duration, it can be divided into 6 subcategories:

• Stage 1: growth of dermal papilla and onset of mitotic activity in the overlying epithelium.
• Stage 2: bulb matrix cells envelop the dermal papilla and begin differentiation, evolving bulb begins descent along the fibrous streamer.
• Stage 3: bulb matrix cell show differentiation into all follicular components.
• Stage 4: matrix melanocytes reactivate.
• Stage 5: hair shaft emerges and dislodges telogen hair.
• Stage 6: new hair shaft emerges from skin surface.

Stage 2: Catagen Phase(rest phase)

This is the shortest phase among the three. Its duration is only about 10 days or so. The hair bulb rests and does not produce anything. Melanin(pigment) production is stopped and the bulb is prepared for the next phase. The purpose of catagen is to delete the old hair shaft factory and to initiate the stem cells of the bulge and the papilla to set the stage for the formation of a new follicle.

Stage 3: Telogen Phase(shedding phase)

This is the stage where the rebirth of hair occurs. New hair starts to grow from the hair bulb after about a 10 day rest from the previous phase. The new hair is responsible for pushing the old hair out of the hair follicle. This is where the shedding occurs. This hair sometimes shows up in your shower drain or when you comb your hair. It can even be seen on your pillow case upon waking in the morning. The rate of hair growth differs from person to person because the cycle is itself is different. Generally, women grow hair at a faster rate than men. Stress, fatigue,and sunlight are all factors that may affect the growth cycle of human hair.