Telogen phase of hair growth lasts for -

Ans. is 'c' i.e., 100 days o The most important feature of hair follicle is that their activity is cyclic. Hair grows at 0.4 mm per day and as it reaches a definitive length, it is shed to be replaced by a new hair. Hair undergoes through 3 different phases of hair cycleAnagen phase (Phase of activity' and growth)This is the phase in which growth of hair takes place -->> Cells in the root of hair are dividing rapidly. Melanogenesis also occurs during anagen phase. This phase lasts for 3 years (2-6 years). Most of the hair (75-80%) are in anagen phase at a given time.Catagen phase (Transition phase)It is the transition phase between anagen and telogen. 3% of hair are in this phase. During this phase growth stops and outer root sheat shrinks and attaches to root of hair - knowm as club hair. This phase lasts for 2-3 weeks.Telogen phase (Resting or degenerative phase)This phase is the resting phase and lasts for 100 days (3 months). About 25-100 telogen hair are shed normally each day. 10-15% of hair are in this phase. After telogen phase the cycle is complete and the new hair, which starts growing in same follicle, pushes this old hair (who has completed the hair cycle) - Old hair is lost and new hair starts growing.o This hair cycle of one hair is independent of the cycle of neighboring hair, i.e., the neighboring hair follicles are not synchronized in growth, this is called Mosaic. The proportion of hair in each phase can be estimated by looking at the plucked hair - called as trichogram.