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What is 'Growth Phase' of the hair? and explain in detail?
Ans. A. AnagenHair Growth CycleScalp hair-follicles have a four phase cycle.Anagen (growth), Catagen (transition), Telogen (resting) and Exogen (hair-shaft evacuation).The Anagen Phase (growing phase)- During the process of folliculo-regenesis, the follicle + epithelial sheath + new hair shaft is recreated.- During its growth (anagen) phase the hair shaft continues to gain length for a period of 2-7 years.- Approximately 80-85% of hair follicles are in anagen.- Hair growth rates range from 0.5cm-1.45cm per month.The Catagen phase (involutionary phase)- mitosis ceases, the follicle enters a period of degeneration.- Catagen accounts for approximately 3% of hair follicles.- The Epithelial sheath shrinks forming a minute "club root" at the proximal end of the hair shaft.- Catagen lasts for approximately 10-20 days.The Telogen Phase (resting or dying phase)- approximately 12-20% of hair shafts are in the amitotic (resting) phase.- Eventually (up to 3 months) the hair shaft vacates the follicle.The Exogen Phase- in which the hair-shaft is evacuated.