introduction

Hair is the head and back of the head parts of the hair. In addition to increased beauty hair people, mainly to protect the head. Can prevent summer sun, winter cold. Soft fluffy hair has elasticity, can resist the lighter collision, can also help head sweat evaporation. The average human hair is about 100000 or so. In all the hair, hair length, especially the woman with long hair, some can grow to a length of 90 ~ 100cm, and even 150cm.
Basic introduction

[ hair ]

Pinyin: T: u F,

He with phonetic: maybe."

English: human hair on top of the head; locks; hair

Hair, or a single called, refers to the long in human head hair. Hair color is genetically determined, in general, common black, golden yellow, brown and red, when human aging, usually silver hair.
Only human hair will always grow, so people often barber, and animals do not have this phenomenon. One of the reasons are not clear.

The average human hair is about 100000 or so.
In all the hair, hair length,冬季中暑
especially the woman with long hair, some can grow to a length of 90 ~ 100cm, and even can be up to 200cm.

Under normal circumstances, hair daily growth of about 0.3 mm, 1 mm in 3 days. Sunlight can accelerate the growth of the hair. Each hair of the life span is generally 2 to 4 years, the longest up to 6 years. If 50 consecutive years of a word, can grow to 6 meters of above. Reportedly,新生兒
India has a monk of dean of Academy of history of China and the United States, his hair was long and 7.9 meters, is the world's longest human hair.
Hair in the world, due to racial and regional difference, has dark yellow, red, brown, red brown, yellow, grey, and even green and red. But also through the hair coloring the hair dyed various colors. Scientific research has proven : the color of the hair with the hair contains metal elements related to the different. Brunette containing equal amounts of copper, iron and melanin, when the nickel content increases, will turn gray. Golden hair containing titanium, reddish-brown hair containing molybdenum,小嬰兒
red brown except copper, iron, and cobalt, green hair is contain too much copper. In some African countries, some children 's hair is red, is a serious lack of protein by.
Yellow and black hair for the vast majority of black, and white people have a variety of colors. Hair is a different color, is because the hair melanin within the distribution of the number of melanin granules, induced by different quantity, density, the hair was black, and hair color is light, sunlight will show different color.
Hair is not associated with the epidermis showed a vertical growth, general tilt angle of 40 degrees 50 minutes, and different parts of hair tilt are not in the same direction, namely the formation of what people say" head vortex".

Such as a large number of falling hair, is a kind of morbid, but mostly in systemic diseases, such as had acute infectious diseases, 強生嬰兒like typhoid fever, scarlet fever, or suffering from chronic diseases such as tuberculosis, anemia, diabetes and endocrine disorders, as well as local cutaneous pathologies, such as alopecia areata, seborrheic dermatitis, can be cause hair loss.
Physiological characteristics

The hair from the bottom to the top can be divided into the dermal papilla, hair, hair root and hairy stem four parts. Physical characteristics and function of hair depends mainly on the scalp epidermis following dermal papilla, hair follicles and sebaceous glands.
Hair follicle hair root in the dermis layer of the inner portion, from the hair root sheath, the outer hair root sheath and the wool ball, inner hair root sheath in hair growth period and hair is directly adjacent to the sheath. Inner root sheath is a hard straight, thick keratin of the tube, which determines when the cross section shape of hair growth. Inner sheath lower three layers: HUXLEY, HENLE sheath sheath and the inner root sheath surface. Before the hair keratin, hair root sheath and hair grow together, the sources are follicles underlying reproduction cell.
In close to the epidermis, hair root sheath and the epidermis and hair follicles from.

Hair follicle dermal papilla is the most lower end, connected with the capillaries and nerve endings. In the hair follicles of the bottom, epidermal cells continuously divide and differentiate. The epidermal cell differentiation in different ways, the formation of hair of different components (such as the cortex, cuticle and medulla etc.), the outermost layer of cells in the formation of inner root sheath. In this phase, the cell is soft and terminal keratinization.
Sebaceous gland function is the secretion of sebum, sebum sebum pipe by extrusion, when the hair through the tube when the sebum, away from the sebum pipe extrusion sebum. Sebum for hair to provide natural protection, endow hair gloss and waterproof performance of.
Arrector pili muscle and epidermis is connected very small muscular organ, it depends on the external physiological environment, arrector pili muscle stretch or shrink. Temperature drop or adrenal hormones, the hair pulled up to a higher position, so that the hair turned up.