Humans have an estimated five million hairs on the body, which are divided so that about 100,000 grow on the scalp and the rest can be found all over the body, except for the palms and soles.
Every single hair is formed in its own hair follicle, which is controlled by the body’s signals to let the hair grow, stop the growth and go dormant or let go of the hair with the result that it falls out.
The length of the hairs is determined by the length of the growth period, but such a period can last for several years when head hair is involved, but on the other hand, eyebrows only grow for a few months at a time.
The growth rate of the hair follicles is controlled by various hormones, but the hair follicles do not respond to them in the same way, so hair grows in different ways in different parts of the body.
For example, male sex hormones have only a limited effect on the growth of hair on the scalp, but a greater effect on the growth of eyebrows and beards.
Women’s sex hormones limit growth on the face and also ensure that the hair follicles in the scalp are kept in place during the growing season, so that the hair there grows for many years at a time.
