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Hair is a structure consisting mainly of keratin with a cylindrical shape and a 65-78µm diameter.
The longitudinal section shows the following regions:
- OSTIUM: the merger of the hair to the outside;
- INFUNDIBULUM: the upper segment that goes from the sebaceous gland duct to the follicle opening on the skin surface;
- ISTHMUS: the middle segment that extends from the sebaceous gland duct to the attachment of the arrector pili muscle. That’s where we find the BULGE, rich in stem cells;
- LOWER SEGMENT: it extends from the base of the hair follicle to the attachment of the arrector pili muscle.
How it works
THE HAIR GROWTH CYCLE
The hair cycle is characterized by the following phases:
Anagen: known as the growth phase, it lasts about 3-5 years;
Catagen: known as the transitional phase, it lasts about 2-3 weeks;
Telogen: known as the resting phase, it lasts about 3-4 months.