The hair follicle is a highly complex system which is of significance as a basic system for processes of general development. If the regenerative capacity of the hair follicle is depleted, various forms of alopecia develop.

The hair follicle is a highly complex system which is of significance as a basic system for processes of general development. If the regenerative capacity of the hair follicle is depleted, various forms of alopecia develop. 

Hair growth is the result of the periodic activity of the cells of the germinal matrix. In the hairy scalp, various phases of the hair cycle take place simultaneously, independent of sex, and are regulated genetically.

The uppermost matrix cells are continually forced up the lumen of the external root sheath. In some distance from the hair papilla, which is their source of nourishment, the keratinization zone begins. Due to the simultaneous development of the internal root sheath (soft keratin) hair is separated from the external root sheath by the medulla (soft keratin) and the hard, peripheral cortex. It represents a continuation of the epidermis into the depth of the skin, which, in the beginning continues to identify the specific horny layer. The epidermal surface structures get farther and farther away from the papilla until only the germinal cells remain. Within the framework of the cyclic growth, the germinal matrix becomes inactive and atrophies. The root of the hair becomes detached from its matrix (telogen phase) and gradually moves up the follicle, gaining for a time a more or less secondary attachment to the external root sheath. The deep part of the external root sheath grows downward again to cover either the old papilla, which becomes rejuvenated, or a new one develops (anagen phase).

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