The anagen or growth phase
During the anagen or growth phase, the matrix cells divide rapidly and move up the hair bulb where they become cells of the hair sheath and hair shaft, i.e. medulla, cortex and cuticle. The final differentiation of the cells takes place in the keratinizing zone. The process is concluded with the production of Keratin, the main component of the hair shaft, and the complete keratinization of the hair root cells. The anagen phase lasts between three and eight years.
