Hair is really a special substance. It is an appendage of the skin and consists of some cells filled with keratin. Keratin also exists in hard tissues such as fingernails and toenails. Hair usually grows anywhere except palms, soles, lips and * * *.
Every hair is fixed in a small hair follicle under the skin. The shape of hair follicle affects the shape of hair. Round hair follicles have long straight hair, oval hair follicles have long wavy hair, and those with curly hair follicles are spiral hair follicles. Hair itself is divided into three layers.
Pigments that determine hair color exist in the middle layer called cortex. Black, brown and blond hair contains different concentrations of melanin, but red hair contains another iron pigment, similar to blood and rust.
Over time, cortical cells will stop producing pigments and individual hairs will turn white. Gray hair doesn't really exist-it's actually a mixture of white hair and primary color hair. Diluted hydrogen peroxide solution is usually used to bleach hair, and these pigment molecules are converted into colorless state by breaking.
The outermost layer of hair, the stratum corneum, consists of multiple layers of overlapping scale cells, which can reflect light and make hair have natural luster. Sebaceous glands connected with hair follicles secrete oil, which plays a role in lubricating and protecting the stratum corneum; The amount of oil secretion determines whether hair is dry or oily.
It seems strange that the human body painstakingly produces such a complex substance as hair, because no one can know exactly what the actual function of hair is. Human hair is longer than that of any other primate. Hair may have been an important species symbol, but for people, it no longer has any real existence value.
Hair has social and cultural significance, and it is also an important part of our personal image.
What is the function of hair?
Human hair has many functions: it can resist direct sunlight and ultraviolet rays or cold invasion, dispel cold and keep warm, prevent sun, reduce impact and protect scalp and brain.
In today's society, hair has become an important part of embellishing people's appearance. Through the modification and combing of hair, women's hair can be black and bright, and their hair styles are beautiful and changeable, just like wearing a crown, which is more charming and beautiful; It can make men's hair dark and thick, more powerful, more energetic and smarter.
Why does the person have hair on his head?
Hair is an important part of the human body, and it is accompanied by beautiful hair from the birth of a baby. Hair is an appendage of the skin. Hair plays a very important role in people's lives.
Beauty function: having a bright black hair, neatly trimmed and transparent, giving people a unique, elegant and beautiful enjoyment when presenting it to everyone; On the contrary, if it is fluffy and dirty, it will give people an unpleasant sense of party.
Protection: thousands of hairs are wrapped around the head, naturally forming the first line of defense of the head. Thick, healthy and clean hair can protect the head from external machinery and bacteria, which plays an important role in fitness.
Sensory function: Hair is sensitive. When the external environment has an impact on the human body, regardless of the wind and rain, or the sun and rain, the first thing you feel is the hair, and the information it sends is transmitted to the brain, thus taking various protective measures.
Regulation: Hair can regulate body temperature. In winter, cold wind blows, blood vessels contract, and hair can keep the head warm; In summer, the sun is scorching, blood vessels dilate, and hair can dissipate heat. Therefore, hair has dual functions of heat preservation and heat dissipation. Hair is a kind of fibrous tissue that grows on the scalp, and it is an arrangement of hard keratin formed by cell regeneration. Hair consists of two parts: root and stem.
Why is the long hair not high?
Height is only related to growth hormone, nutrients needed by bones and the growth environment of bones, and has nothing to do with hair. Generally speaking, girls aged 65,438+08 basically stop growing. You need more exercise (basketball, skipping rope, etc. ) to grow bones, eat more bone foods (cartilage and tendons) to supplement nutrition to continue to grow taller.
Why do people have long hair?
In the process of human evolution, that is, in the process of standing, people's heads directly face the sun and are directly affected by the negative effects of precipitation on their heads. Especially after human beings stand, the head becomes the highest point of human beings and the softest weakness of the whole body. In order to make up for the unfavorable factors brought by soft rib to human evolution, the hair in other places was gradually removed during the evolution, but the hair on the head was not removed during the evolution. On the contrary, it grows to the hair. Over-the-shoulder hair can not only protect the head in all directions, but also play an early warning role, such as keeping the ears warm in winter, and can also play an early warning or protection role for the neck. Of course, since the development of mankind, the weakness of the head has long been compensated by civilization, that is, the function of hair has long been replaced by civilization, making the original function of hair become the function of human beauty today. In other words, people grow hair in order to adapt to the natural environment and the changing needs of human beings in the process of evolution, so people grow hair.
Why do people have long hair? What are the benefits of hair to people?
Hair can only grow on the head. Under the microscope, the hair follicles of the hair pulled out of the thigh look the same as those of the hair. Anatomically speaking, the hair in our armpits, legs and other parts of the body is the same as hair. However, the experiment of hair transplantation shows that the growth mode of hair is determined by its location. When people transplant hair, they often take a hair from one part of the head and transplant it to another part of the head, because if they transplant hair from other parts of the body, it will not be successful. Similarly, if they transplant their hair to other parts of the body, their hair will not grow smoothly. Dr. nuefeld said: "When researchers transplant hair from head to leg, it won't be as long as it is on the head, but the hair transplanted to the leg will be longer than the hair on the typical leg." Hair and body hair grow periodically. In the active stage called "growth period", the hair follicle grows a lock of hair, and then the growth rate slows down, and the hair follicle will "rest" for a while. This stage is called the "rest period" stage. When the hair falls off, it will reach the "exogenous" stage, and when the "growth period" begins again, the hair follicle will grow a new lock of hair. Hair on legs usually grows for 19 to 26 weeks and then falls off, while hair can grow for 2 to 6 years.
Hope to adopt
Why does my hair grow so fast?
Hair is the fastest growing hair, generally 0.27-0.4 mm long every day, about 1.0 cm long every month and one year long 10- 14 cm.
Hair growth rate is mainly affected by the following factors:
(1) gland
① gonad: Androgen plays an important role in the growth of hair mother cells.
② Adrenal gland: If the androgen secretion of adrenal cortex is strong, it can cause hirsutism in women. But it is also related to the function of pituitary gland. If the pituitary gland function deteriorates, the hair may be reduced or shed.
③ Thyroid gland: Normal thyroid function plays an important role in hair growth. If it is dysfunctional, the hair on the outside of the eyebrows (1/3) will fall off. When the function declines, not only the color will be grayish white, but also the hair will decrease or fall off. The growth and shedding of hair are mainly controlled by the growth period of hair itself, but also influenced by race, endocrine, disease, mental state, gender, age, season and other factors.
(1) Race: Racial differences are obvious phenomena. People of different races not only have different hair colors, but also have different hair quantity and growth conditions. Baldness is common among whites, less in China and even rarer among Indians. (2) Heredity: In the same family, the growth of hair is often roughly the same. Male baldness is closely related to heredity.
(3) Endocrine: Androgen can directly act on hair follicles, leading to male baldness. People who lack androgen (such as eunuchs) will not have this phenomenon. Estrogen has the function of antagonizing androgen, so women seldom go bald before menopause. Hair thinning when thyroid hormone is insufficient, hair loss when adrenal gland function is low, and the function of anterior pituitary gland is reduced, which can lead to total baldness.
(4) Mental state: nervousness, fear and anxiety can obviously increase hair loss. It is reported that a condemned man loses more than 1000 hairs every day after being sentenced.
(5) Vitamins: Long-term lack of vitamin A will lead to thinning hair; Lack of vitamin B2 will increase sebum overflow, which will increase sebum overflow and make hair fall off easily. Vitamin B6 deficiency can lead to abnormal sebum secretion. Oral contraceptives can speed up metabolism and consume more vitamin B6, which may be related to diffuse hair loss in some women. In addition, vitamin B6 can affect the process of pigment metabolism, and when it is lacking, hair will turn gray and grow poorly; Deficiency of pantothenic acid (also called vitamin B3) will make hair turn white and grow poorly; Inositol belongs to vitamin B family, which can prevent hair from falling off. Lack of biotin (also known as vitamin H2) can make hair fall off; P-aminobenzoic acid also belongs to B vitamins, which can protect hair color and maintain normal hair growth. (6) Trace elements: Some scholars have observed the changes of trace elements such as zinc, iron, molybdenum, calcium, lead, magnesium, manganese and selenium in hair, and found that the values of zinc, copper, iron and manganese in patients with alopecia decreased significantly, while the values of calcium, magnesium and selenium increased significantly, and there was no difference among patients with atypical alopecia. Copper deficiency will affect the absorption and utilization of iron, poor iron metabolism will lead to anemia, mental excitement and other symptoms, the latter can be the cause of alopecia areata, copper deficiency will also affect the process of hair keratinization, thus affecting hair growth; Calcium plays a role by combining with calmodulin, and high calcium concentration may change the immune regulation function of the central nervous system, thus leading to hair loss; Excessive selenium will lead to hair loss due to autoimmune reaction and sebum overflow.
(7) Diseases: Some systemic diseases, such as febrile diseases, anemia, malnutrition, liver diseases and serious chronic wasting diseases, often lead to thinning hair.
(8) Gender and age: Women's hair grows faster than men's, and young people grow faster than the elderly, but this difference is not great. With the increase of age, the number of hair follicles in the head decreased significantly. According to statistics, according to the number of hair follicles per square centimeter, there are 6 15 in 20-30 years old, 485 in 30-50 years old and 435 in 80-90 years old.
(9) Other factors: Hair grows slightly faster in summer than in winter. This is because the increase of temperature can promote vigorous metabolism and lead to faster hair growth. Hair grows faster during the day than at night. X-ray can control sulfhydryl compounds in hair follicle matrix, thus causing temporary hair loss. Some chemical factors such as iron will affect the formation of keratinization, which may interfere with cystine's participation in keratin composition, thus affecting hair growth. Ultraviolet rays, drugs, trauma, chronic inflammation, skin diseases, local * * * *, etc. It also has a certain effect on hair growth and shedding. ...
Why do people have long hair?
You can't even say that you are a talent ~ ~
The barber's master is going to live! Hey, hey, just kidding.
Hair is really a special substance. It is an appendage of the skin and consists of some cells filled with keratin. Keratin also exists in hard tissues such as fingernails and toenails. Hair usually grows anywhere except palms, soles, lips and * * *.
Every hair is fixed in a small hair follicle under the skin. The shape of hair follicle affects the shape of hair. Round hair follicles have long straight hair, oval hair follicles have long wavy hair, and those with curly hair follicles are spiral hair follicles. Hair itself is divided into three layers.
Pigments that determine hair color exist in the middle layer called cortex. Black, brown and blond hair contains different concentrations of melanin, but red hair contains another iron pigment, similar to blood and rust.
Over time, cortical cells will stop producing pigments and individual hairs will turn white. Gray hair doesn't really exist-it's actually a mixture of white hair and primary color hair. Diluted hydrogen peroxide solution is usually used to bleach hair, and these pigment molecules are converted into colorless state by breaking.
The outermost layer of hair, the stratum corneum, consists of multiple layers of overlapping scale cells, which can reflect light and make hair have natural luster. Sebaceous glands connected with hair follicles secrete oil, which plays a role in lubricating and protecting the stratum corneum; The amount of oil secretion determines whether hair is dry or oily.
It seems strange that the human body painstakingly produces such a complex substance as hair, because no one can know exactly what the actual function of hair is. Human hair is longer than that of any other primate. Hair may have been an important species symbol, but for people, it no longer has any real existence value.
Hair has social and cultural significance, and it is also an important part of our personal image.
What is the function of hair?
Human hair has many functions: it can resist direct sunlight and ultraviolet rays or cold invasion, dispel cold and keep warm, prevent sun, reduce impact and protect scalp and brain.
In today's society, hair has become an important part of embellishing people's appearance. Through the modification and combing of hair, women's hair can be black and bright, and their hair styles are beautiful and changeable, just like wearing a crown, which is more charming and beautiful; It can make men's hair dark and thick, more powerful, more energetic and smarter.
Why do people keep their hair?
I've always wondered why people keep their hair. If it is the problem of animal evolution, the hair on the body gradually degenerates or almost disappears in the process of evolution from monkeys to humans, while the hair growth is constantly strengthened, belonging to the type of "wildfire is unlikely to devour them, and the spring breeze is high". Looking at all the animals in the world, there is no endless hair. Do people have lion genes? But even the lion's hair will stop growing when it reaches a certain length. According to the survival law of nature, some people say that ancient people wore more animal skins and less animal hats, so the body hair degenerated because it lost its protective function, and the hair was preserved or strengthened because it needed to keep warm, but this doesn't make sense. According to experts, the head is the least afraid of cold in human tissues, and everyone may feel this way. I have had the experience of washing my hair with cold water on snowy days. I didn't feel cold, but it is impossible to take a cold shower unless my brain is broken. It suddenly occurred to me that all this may be God's arrangement, so that some people can have a livelihood to support their families. It is precisely because people have hair, and it keeps growing, that they have a job as hairdressers or now they are called hairdressers. When you are busy all day, there is reason to get a haircut to avoid work. When you have more money than you can use, someone will spend it or transfer it for you and cut a leek on your head. You even foolishly called it a "beautiful cut". Having said that, I actually had a very vicious idea. Anyway, with the development of science and technology, those guys who want to win the "Nobel Prize" can invent a medicine, which can stop hair growth or even grow nothing after eating it. In that case, the world will be dazzling during the day and how much energy can be saved at night, hehe! (Except for Africa, their ancestors can only be blamed), if so, the inventor may even have won the Nobel Prize for environmental protection. Having said that, you may feel bored, because in today's gossip, if you don't pay attention, it will be deleted. If you are busy for a long time, you might as well move your fingers, and half a day's work will be wasted, or you will be bored if you post it. The idea about hair is based on the feeling of 12 thousand yuan in Zhengzhou two days ago.
Why does human hair grow?
Let scientists scratch their heads. When you go to the library one day to find the answer, you will find that apart from musk oxen, human beings are almost the only animal whose hair has been growing. Why on earth is this? But you can't find the answer from the library shelves at all, because no one has been able to solve the mystery so far. In the past few years, scientists have become more and more interested in studying human hair. A short article published in the American journal Evolutionary Anthropology by Arthur Newfield, a physiologist at Northwestern University, and Glenn Conroy, an anthropologist at Washington University in St. Louis, was the first person to discuss this issue. They pointed out that other mammals' hair will automatically stop growing when it reaches a certain length, but human hair will continue to grow. They asked in the article: "Have you ever seen chimpanzees comb their hair? Or have you ever seen any long-haired animals need a haircut? " Of course not. Why on earth can human hair keep growing? At present, people don't know much about this problem. Hair grows on the surface of human body except palm and sole. Human hair can be divided into soft hair and hard hair according to its thickness and hardness. Soft hair, commonly known as hair, is soft and light in color and spreads all over the skin surface; Bristles are thick and hard and grow in some parts of the human body, such as hair. For adults, under the control of complex hormone mechanism, these two types of hair can expand into a variety of hairs, such as eyebrows, eyelashes, armpit hair, beard and so on. Both smooth hair and tiny toe hair can grow at the rate of 1 ~ 1.5 cm per month, and the hair stops growing for a very short time before falling off. Different parts of the body have different hair lifetimes, which can determine their final length. For example, leg hair can last for about 2 months, armpit hair can last for 6 months, but hair can last for 6 years or even longer. When hair grows to a certain period, it begins to fall off and be replaced. The replacement of human hair is not seasonal like that of mammals, but often falls off and is gradually replaced throughout life. According to statistics, there are10 ~ 200,000 hairs, including 80 ~14,000 hairs in the head, 20,000 hairs in the trunk and limbs, and 30 ~ 120 hairs fall off every day. The life span of different parts of hair is different: the life span of hair is 2 ~ 5 years; Beard for 2 ~ 3 years; Axillary hair 1 ~ 2 years; * * * 1 ~ 1.5 years (the life span of beard and armpit hair and * * * is only 7 ~ 10 months); The life span of eyebrows and eyelashes is 3 ~ 5 months. In addition to natural shedding at the end of life, hair may also fall off due to poisoning, disease or violence. Gene mutation may be the main reason. As for how to control hair growth, there are still many uncertainties, and scientists have not solved some mysteries. But the growth of hair may be related to countless genes. Moreover, even if only one gene changes, it will have a great impact on hair growth. Take Angora rat as an example. Its long hair is related to a gene mutation called FGF5, which is a protein that prevents hair growth. Nuefeld and Conroy believe that the reason for the sustained growth of human hair may be that FGF5 or similar gene mutation has lost the function of inhibiting hair growth. Another possibility is that the gene of 10 main keratin (an insoluble and hard protein substance, which is the main structural component of hair, nails, horns and hooves) contained in hair is constantly copied. Scientists have pointed out that nine kinds of keratin in humans, chimpanzees and gorillas are almost the same, but the tenth kind-PHI-HHAA is obviously different. Although for humans, phi-hHaA is a pseudogenetic factor (that is, a part of DNA of deoxyribonucleic acid, which is similar to genetic factor, but has no genetic function and cannot synthesize protein), it is a mutant protein in other primates. In 200 1 year, Helmilita Venter of the German Cancer Research Center published his discovery: this gene mutation appeared 240,000 years ago. Which is more attractive, short hair or long hair? Short hair has many advantages over long hair: first, it is more conducive to health care, because long hair is more likely to breed parasites; In addition, it is also beneficial to regulate body temperature. Short hair can make human ancestors better adapt to the climate from jungle to savanna. Some people even think that keeping short hair is the adaptation of ancestors to life by the water. Darwin believes that sexual orientation is the key: people with short hair look more attractive than those with long hair, so there are more descendants, more people and fewer people with long hair. Although short hair has many advantages, the fact is that humans prefer long hair, and hair has become thicker and thicker in the process of evolution, you know. ......
Why do women have long hair?
Ancient men also had long hair.
It was because parents were endowed with body and skin. ..
In the late Qing Dynasty, more and more people in China went abroad to study.
Many young people are aware of the progress of foreign countries and want to learn from them.
Just like the change of clothes, men began to wear suits. ..
China has learned from foreign countries in life, diet and thoughts. Men cut off their braids.
Women still keep it. At that time, women were not really liberated, and it was considered immoral to cut hair.
Probably because of women's personality, they all have long hair now. ..
On the one hand, the gender is clear.
On the other hand, women's hair is also the most natural embellishment.
Furthermore, it is also an aesthetic habit.
The long and fluttering women in China's costume dramas really contain oriental beauty.
Western blondes are also sexy and charming. ..