Hair Growth Cycle
Hair growth occurs in cycles throughout an individual's lifetime. The three stages or phases of hair growth are the Anagen, Catagen, and Telogen. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form.
Anagen Phase - The anagen phase is known as the active growth phase. It begins in the papilla and can last from two or more years. The span of the hair remains in this stage of growth is determined by genetics. Scalp hair may remain in the anagen for up to 3 years. The longer the hair stays in the anagen phase, the longer it will grow. During this phase, the cells in the papilla divide to produce new hair fibers, and the follicle buries itself into the dermal layer of the skin to nourish the hair strand.
Catagen Phase - Signals sent out by the body determine when the anagen phase ends and the catagen phase begins. The catagen phase also known as the transitional phase. It allows the follicle to renew itself in a sense. During this time, which lasts about two weeks, the hair follicle shrinks due to disintegration and the papilla detaches and cutting the hair strand off from its nourishing blood supply. While hair is not growing more during this phase and shed off.
Telogen Phase - The Telogen phase is known as resting phase. In this phase follicle remains dormant anywhere for months, depending inversely on the number of actively growing hair in the area, i.e. the scalp has a shorter telogen phase than the chest. In this phase the epidermal cells lining the follicle channel continue to grow as normal and may accumulate around the base of the hair. At some point, the follicle will begin to grow again, within two weeks the new hair shaft will begin to emerge. Once the telogen phase is complete the anagen phase begins again to repeat the cycle. This is called hair growth cycle.