( For the texts and pictures books, publications, guidelines for example in awmf.org and contributions of colleagues were consulted.)
The life cycle of a hair on the head is 3-4 years. It is composed of the anagen (growth), the catagen (antenatal) and telogen (resting) phase.
This leads to the physiological hair loss (60-100 head hairs per day). Since the phases of the various hair run asynchronously on the head, it comes to regular failure of the entire coat.
The anagen lasts approximately 3 years, the catagen three weeks and telogen for about 3 months. Accordingly, at least 85% of the scalp hairs in the anagen phase, 10-15 % in the telogen phase and 0.2-1 % are in the catagen phase. Furthermore, the cycle is influenced by external signals (hormones, growth factors, neuropeptides from nerves).
In hair loss, thinning of scalp hair with hair loss occurs with increase of the telogen hair in contrast to the anagen (growth phase). In severe disorders (severe infections, poisoning) there is not only a higher proportion of telogen hair, but also deformed (dystrophic) hair.