subject: Life Cycle Of Hair [print this page] Do you know in general an individual can have around 100,000 to 125,000 hair fibers? A normal individual may have different types of hair growth in different areas of their scalp. This happens because of the dynamic nature of the hair growth structure which is known as the mosaic style. At some places we have thick hair growth while at other places we have very thin hair. Hair growth depends and differs from race to race. For example the Africans and Asians have thinner hair that that of the Caucasians. The term follicular unit was first emerged in 1984 by John T. Headington who researched on a punch biopsy in a transverse way.
What is meant by Follicular Unit?
Usually a follicular unit of hair consists of one, two or three fibers of hair. Rarely has it been seen that it is containing four of five fibers. These hair fibers are enclosed by collagen band. The follicular unit also includes the area with related sebaceous gland as well as arrector pili muscles which remains attached to every fiber. Almost all the hair in the scalp is made from the follicular units that have two to three hair fibers.
Life Cycle of Hair
Like every other living thing hair also goes through different phases in its life cycle. The general hair life cycle includes stages like elongation, thinning and hair loss. Each and every hair fiber is independent and can have different phase of life at a certain phase. The life cycle of hair can be divided in mainly three phases. These three phases are:
Anagen Phase During the anagen phase the hair follicles remain healthy and thick. It also remains in its continuous elongation. Usually around 84 to 90% of the hair follicles are always found in its anagen phase. This phase lasts for three years or so.
Catagen Phase This is the transition phase. In its catagen phase the transition takes around three weeks. In this phase of hair life cycle the apoptosis or programmed cell death gets initiated. The catagen phase experiences the shrinking of the papillae while the hair follicles get elevated in the scalp. The pigmentation of the hair lowers down and the hair also starts to thin. Around 2% of the hair in a scalp is found in the catagen phase.
Telogen Phase This is the last phase that remains for three months approximately. In this phase the thinning hair falls and new hair is produced from the hair stem cells.
