Hair Growth Cycle

Life Cycle of Hair Growth

Background

Hair is the focus of attention to most people. Hair is often the most prized possession of a person. There are so many things which can be done with hair to change a person’s appearance. Considering the importance of hair to most people, in this section we shall study the different stages of hair growth in what is known as the “hair growth cycle”.

Growth of Hair

The time taken for a single strand of hair to grow is from two to six years. During the period of growth, shampooing washing, conditioning and exposing it to heat at times when heated curlers or a hair dryer are used can destroy the shaft of the hair which may result in split ends and hair fall.

Hair Growth Phases

There are four phases of hair growth:

  1. Anagen which lasts for 2 to 8 years.
  2. Catagen lasting for 2 to 4 months
  3. Telogen lasting for 2 to 4 months
  4. Exogen Phase

Anagen Phase

This is the longest period in the hair growth cycle. This phase lasts for up to 2 years during which 90% of the normal scalp follicles are active. It is this phase which decides how long the hair will grow.

This is also a period where the lower part of the follicle will experience regeneration and re-growth. In this stage, the epidermal cells which surround the dermal papilla form the hair roots. During this phase, there is a constant multiplication of cells. The new cells push the old cells out of the scalp thereby causing the hair to grow.

Catagen Phase

This phase of the hair growth cycle is marked with major destruction of the follicles. On the completion of the catagen phase, the growth of hair follicles comes to a halt and the hair starts to degenerate. The papilla cell fibroblast projections situated in the basement membrane withdraw.

Telogen Phase

This a resting phase in the normal hair growth cycle. This stage marks the end of the growth of a follicle. The hair which is formed in this stage is known as “club hair” as the cluster of cells at the end of the follicle gives a club-like appearance to the hair fiber. In this stage, the hair is still attached to the scalp but it can come out easily by washing or combing.

Exogen Phase

This is the phase of hair shedding. About 50 to 150 hairs are lost a day. The mechanics of the exogen phase are not clearly understood but it has been observed that this phase has a definite relation to the anagen phase.

Conclusion

By understanding the different phases of the hair growth cycle, it is possible to focus on those phases which are sensitive to hair fall. By using the right approach, it is possible to take preventive measures to reduce hair fall to the minimum and keep the hair strong and healthy.