Hair is a lot more complex than it looks on the surface. We know it plays a vital role in appearance and also transmits sensory information. To better understand the process of hair loss, It is important to understand the process of hair growth. Hair growth follows a specific growth cycle with three distinct and concurrent phases. These are the Anagen, Catagen and,Telogen phases.
Each of these phases has specific features that affect hair length. It is also important to note that at any given time each strand of hair will be in one of the three stages of hair growth. A strand of hair might be in the catagen phase, while another might be in the telogen phase. This occurs in other parts of the human body where hair grows. Once the hair growth cycle is complete, the cycle restarts and a new strand of hair begins to form.
The anagen phase is the active phase of the hair. This phase is also known as the growth phase. The cells in the root of the hair begin to divide rapidly. Hairs in the anagen phase grow approximately 1cm every 28 days. The amount of time hair remains in this stage of growth is determined by genetics. However, it is usually estimated to be between 2 to 6 years. The longer hair stays in the anagen phase, the longer it is expected to grow.
Some individuals experience difficulty growing their hair beyond a certain length because they have a short anagen phase. Hairs on the arms, legs and eyebrows also have a very short anagen phase of about 30 – 45 days, which explains why they are shorter that scalp hair. At any given time, approximately 85% are in the anagen phase at any given time.
At the end of the anagen phase, the hair enters the catagen phase. This is a transitional stage in hair growth and about 3% of hairs are in this phase at any given time. This phase is estimated to last about 2 weeks. This phase of the hair growth cycle allows the follicle to renew itself. The hair follicle shrinks as a result of disintegration and the papilla detaches, which cuts the hair strand from from its nourishing blood supply. The follicle becomes a sixth of its original length, which causes the hair shaft to be pushed upward. This process is what leads to the formation of club hair.
Finally, hair leaves the catagen phase and enters the telogen phase. This phase is also known as the resting phase. During this phase, hair follicles remain dormant for 1-4 months. Approximately 10% of scalp hairs are in this phase of hair growth at any given time. This phase lasts for about 100 days for hairs on the scalp and even longer days for hairs on other parts of the body. The hair follicle is completely at rest during this phase and club hair is completely formed. uprooting hair in the telogen phase will reveal a solid, hard, white material at the roots.