Head hair refers to the hair on the head as opposed to the rest of the hair on the body. The human hair is between 0.05 and 0.07 millimeters thick, although there are smaller individual but also origin-related differences. The thickness of the hair decreases with increasing age.
The hormone balance also has a negative influence. There are also some differences in the number of hairs on the head when comparing different countries. Europeans have about 121,000 head hairs, which are distributed over 226 hairs per square centimeter.
Asians, for example, have about 89,000 hairs, but often thicker hair. According to this, ethnicity and also age has an influence on the number of hairs. Every day a person loses about 100 hairs a day, which is considered normal.
Color
Blond, brown, red, black or even grey, many different hair colors are possible in humans! Which hair color finally forms depends, among other things, on the genes and the melanin content in the cells of the hair. Melanin is a color pigment, which is produced by certain cells, the melanocytes.
It is also responsible for the coloration of the choroid and the skin in general. The pigment melanin is divided into two different colorants. The brownish-black dye is eumelanin.
This can be distinguished very well from the lighter yellow-reddish pheomelanin. The skin color of a person is determined by the genes as well as the ratio of eumelanin to phaeomelanin. For example, people with lighter skin and reddish shimmering hair have a higher pheomelanin content. In addition to red hair color, phaeomelanin is also responsible for light blonde and blonde hair types
Growth
The growth of hair is determined by genes. They determine the life span, the structure and also the growth cycle of the head hair. The growth is based on hair bulbs, whose core is located in the hair papilla.
The growth of the hair takes place in 3 phases. The anagen phase is the time in which the hair grows a lot. The hair cells divide very quickly and thus form a lot of new hair substance, the keratin.
On the head there is usually 80 to 90 percent of all hair. The years grow by 0.4 millimeters per day, which eventually adds up to one centimeter per month. The hair cells remain in this active state for about three to seven years.
This period varies from person to person, as the life span of hair is genetically determined. But the hair does not grow endlessly and after the mentioned period of time, it goes into a transitional phase. In this phase, called catagen phase, there are about three percent of the hairs on the head.
Some altered processes take place in the hair root, which means that the hair root is less supplied with nutrients and becomes increasingly keratinized. This phase lasts about four weeks. Afterwards, the hairs change into the telogen phase.
In the period of about two to four months, about 15 percent of the hair is located. The attachment of the hair becomes even looser. After all, even light stress such as combing or washing can cause the hair to fall out.
Hair and hair root are separated from each other. On the basis of the root, one can therefore estimate in which phase the hair is in. This knowledge can be particularly important if diseases such as hair loss are present. Here, a pathological acceleration of the hair cycle can be the cause of increased hair loss.
