Why are there different classifications of hair？

Every life species has been formed after the evolution of Renwan-year Wujingtianshu. Therefore, for animals, whether they are carnivorous tigers in the jungle at the top of the food chain or zebra antelopes eating grass on the grassland at the bottom of the food chain, each organ of these animals has its own reason for existence after being selected for use or retirement.

The same is true of human hair. In order to keep warm and cold in the jungle era, in order to resist the thorns of nature, early humans were also covered with thick long hair like apes and monkeys. so what? As humans walked upright and walked out of the jungle, they found fire. They invented the idea that silkworms and weaving began to knot and live. Humans gradually shed the long hair on their bodies and retained useful hair.

These hairs can be divided into lanugo and vellus hair terminal hairs in terms of length and thickness. The terminal hairs can also be divided into long hair and short hair. Generally speaking, the hair more than 1 cm is long hair, such as hair, beard and armpit hair; Below 1cm are short hairs, such as eyebrows, eyelashes, nose hair. In addition to the length standard, the internal structural feature of the terminal hair is hairy medulla and the appearance feature of melanin is thick and thick. The place where the final hair is densest is at the top of the head of the human body in the form of thick hair. The average surface of the head of the human body is 500 square centimeters, while the hair of normal people can reach 100000~125000 in total at 250 hairs per square centimeter.

The vellus hair is the hair that we often say spreads all over the body except for the lips, hands, feet, palms, nipples, glans and pedicels of the genitals. Its internal structural characteristics are hairless medulla, light pigment, and its external characteristics are soft and thin. The densest place of vellus hair is also on the top of the human head, accounting for about 10% of the normal human hair.

According to the name, fetal hair means that most of the fetal hair that grows in the mother's belly becomes vellus hair at 8 months. A small part of fetal hair also comes out of the mother's belly when the baby is born. The internal structural feature of lanugo is that it has neither medulla nor pigment. Its external feature is as thin and soft as vellus hair. Once the lanugo falls off, it will not regenerate for life. Because of this, some parents kept the lanugo and lanugo hair on the boy's head in the countryside in the early days, leaving a thin line of hair as a souvenir of life growth.

From the perspective of hair function, both the terminal hair and vellus hair have the function of controlling the body temperature and keeping the body at a constant temperature by shrinking the hair in winter to keep warm, and opening the hair to sweat in summer.

The role of hair in the final hair is far greater than that of short hair and vellus hair, such as protecting the head from trauma and preventing ultraviolet

For women, hair is equivalent to the second test. Women can frequently go into the beauty salon to whiten, but the skin color is not white and there are not many lines, which can only be found at a close distance. However, it can be observed from a distance that the thick, thin and dense hair is still thin, dark or gray, that is to say, the features of people are not close. This is why for many young women, hair care has become a part of beauty, even beyond the beauty of the test department.

In the traditional Chinese medicine, hair is also the reference data for Chinese medicine to judge diseases. The abnormal attenuation of liver and kidney function and endocrine, and the difference of insufficient nutrition of qi and blood and unhealthy mental pressure can be seen from hair. Modern medicine can infer the conclusion of many diseases from the test results of a hair, especially the detection results of human trace elements. It can be said that hair is a barometer of human health.

The beard in the long hair shows male gender characteristics; The armpit hair plays a role in relieving friction and protecting the skin under the armpit when the two hands swing during human walking. The hair plays a role in protecting the root of life and the spring of life during frequent friction in human reproduction.

After talking about the long hair in the final hair and then talking about the short hair in the final hair, these short hairs are also responsible for different parts of the human body. Eyebrows and eyelashes protect eyes by shielding dust; The nose hair fills the nasal cavity like a guard, which acts as a barrier to prevent dirt from penetrating.

After talking about the long hair in the final hair and then talking about the short hair in the final hair, these short hairs also bear significant responsibilities because of the different parts of the human body. The eyebrows and eyelashes protect the eyes by shielding the dust. The nose hair fills the nasal cavity like a guard and acts as a barrier to prevent the dirt from penetrating.

And the vellus hair, which covers every inch of the body, is arrayed to wait for the cold winter and close the city gate to resist the wind and cold; Once the scorching heat reaches the cave door, it can release sweat and heat to become a natural regulator to stabilize human body temperature.

Like every internal organ of life, the lanugo and vellus hair end hair are always different with human life. The attenuation of internal organs is invisible, but the attenuation of external hair can be seen directly. For example, from the formation of the fetus to the beginning of birth, the lanugo hair on the top of the head replaces the lanugo hair, and the lanugo hair on the top of the head is as long as hair; Long hair replaced vellus hair to achieve balance in childhood; In youth, the vellus hair decreased significantly, and the hair on the top of the head was basically long; After old age, hair follicles degenerate, hair length decreases, and the number of vellus hairs does not change, but obviously increases. For some male hair loss, long hair is directly transformed into vellus hair, which is called hair follicle formation in hair science.

The hair primary school asks many questions. We cherish our lives and our hair. We must learn from teenagers that "hair does not pull out". Don't think your hair is thick and you don't know how to cherish it. It's too late to regret when your hair is sparse.