A cycle of hair growth characterized by three phases, see trichogram below.
- Anagen phase (growth phase): Duration about 2-6 years (refers to the capillitium). The hair is located deep in the dermis, encompassing the papilla like a push-button (anagen hair). High metabolic activity of the matrix with high mitosis rate.
- Catagen phase (transition phase): duration about 1-2 weeks. The hair rounds itself basally and is enclosed at the lower pole like a cuff by the outer root sheath (catagen hair). The metabolic activity of the matrix has ceased.
- Telogen phase (resting phase): duration about 100 days. Coloured, ascending hair, the inner root sheath is missing (telogen hair). A new anagen hair in the depth expels the telogen hair. The ratio of anagen hair to telogen hair is 10:1. 75,000-150,000 hairs in a head vary between 50 and 100 per day (<20% for men, <15% for women, <10% for children).