I. Protective functions
(a) Defense against mechanical stimuli The skin covers the surface of the body, and the cells of the epidermis layers are closely connected. The dermis contains a large number of collagen fibers and elastic fibers, making the skin both tough and soft, with a certain degree of tensile and elastic. When rubbed or pulled by external forces, it can still remain intact and recover its original state after external forces are removed. The subcutaneous tissue is loose and contains a large number of fat cells, which has a cushioning effect and can slow down the impact of external forces and protect the internal tissues from damage.
(B) defense against physical stimuli blocking electric current, blocking ultraviolet rays, preventing evaporation of water from the body and infiltration of water from outside the body. The stratum corneum is a bad conductor and has a certain insulating ability against electric currents, which can prevent a certain amount of current from harming the body. The stratum corneum and melanin particles can reflect and absorb some of the ultraviolet rays, preventing them from entering the body and harming the internal tissues. With prolonged sun exposure, the stratum corneum of the skin will thicken accordingly, melanin particles will increase, and the appearance of the skin will become rough and the skin tone will deepen. The sebaceous glands secrete sebum and the sweat glands secrete sweat, which mixes to form an emulsified skin film on the surface of the skin. It moisturizes the stratum corneum, prevents the skin from drying and cracking, and stops the evaporation of water from the body and the penetration of water from outside the body.
(iii) Defense against chemical irritation The main component of stratum corneum cells is keratin, which is resistant to corrosion by weak acids and bases. Sweat can dilute the acidity of chemical substances to a certain extent and protect the skin.
(D) defense of biological stimulation of the skin surface sebaceous film is weakly acidic, can prevent the invasion of bacteria and fungi on the surface of the skin, and has antibacterial, bactericidal effect.
Second, the skin of the regulation of body temperature function of the human body to carry out a variety of normal life activities need a relatively constant body temperature to do to ensure
The normal body temperature is around 36-37 ℃. The skin plays an important role in thermoregulation. The skin regulates body temperature in two ways.
(a) over the vascular regulation of body temperature when the external temperature is high, the skin capillary network a large number of open, the body surface blood flow increased, the skin heat dissipation increased, so that the body temperature is not too high. When the temperature is low, the skin capillary network partially closed, part of the blood flow from the arteries not through the body surface, directly by the arteriovenous anastomosis branch into the veins, so that the body surface blood flow is reduced, reduce heat dissipation, to maintain body temperature.
(B) through the evaporation of sweat glands to regulate body temperature when the temperature is high, the body sweats a lot, the process of evaporation of sweat can take away part of the body heat, play a role in reducing body temperature.
Third, the sensory function of the skin skin contains a wealth of sensory nerve endings
Can feel a variety of external stimuli, producing a variety of different sensations, such as touch, pain, pressure, heat, cold, etc.
Fourth, the skin’s secretion and excretion function
(A) secretion function sweat glands can secrete sweat, sebaceous glands can secrete sebum. Sebum mixes with sweat on the skin surface to form an emulsified sebum film, which moisturizes and protects the skin and hair. There are many factors that affect the secretion function of sebaceous glands, mainly the following aspects.
1, endocrine influence androgen and adrenocorticotropic hormone can make sebaceous gland gland hypertrophy, secretion function is enhanced. So generally male skin is more oily than female skin, with large pores.
2, the influence of external temperature when the temperature is high, sebum secretion is more; when the temperature is low, sebum secretion is reduced. Therefore, our skin is more oily in summer, and in winter, the skin becomes dry.
3.The influence of skin surface humidity The humidity of the skin surface can affect the secretion of sebum diffusion. When the moisture on the skin surface is high, the sebum is easy to emulsify and spread; while when the skin is dry, the secretion and spread of sebum will become slow.
4. The influence of age: sebum secretion is low in childhood; secretion increases in adolescence; and gradually decreases after 35 years old. Therefore, the skin of children and middle-aged people is dry, while the skin of adolescence is oily.
5, the influence of diet greasy food, spicy stimulating food can make sebum secretion increase. Therefore, people with oily skin, especially those with acne, should not eat sweet, greasy and stimulating foods.
(b) Excretory function of the skin excretes the waste produced by metabolism in the body through sweating, such as uric acid and urea.
V. The skin’s respiratory function skin can also breathe through sweat holes and pores, absorbing oxygen directly from the air while expelling carbon dioxide from the body. Its respiratory capacity is about 1% of the lungs. The facial stratum corneum is thin, capillary-rich, and directly exposed to the air, its respiratory function is more prominent than other parts of the body, usually too thick makeup or with makeup for too long, will affect the skin’s breathing, which is not good for the health of the skin.
Six, the absorption function of the skin is not absolutely dense impermeable skin, it can selectively absorb external nutrients
(a), the skin absorption pathway skin directly from the outside world to absorb nutrients in three ways.
1, nutrients penetrate through the stratum corneum cell membrane and enter the keratinocytes.
2, a small amount of macromolecules and water-soluble substances can be absorbed through the pores, sweat pores.
3, a small amount of nutrients penetrate into the dermis through the surface cell interstices.
(2) The absorption capacity of skin for various substances is related to the physical and chemical properties of the absorbed substances.
Fat-soluble substances are easily absorbed. The skin’s absorption ability of animal fat is strong, so mink oil, lanolin, guano, etc. have good nourishing effect on the skin. The skin has the second highest absorption capacity for vegetable oils, and the worst absorption capacity for mineral oils. The skin has a certain absorption capacity for vitamin classes. Fat-soluble vitamins are easily absorbed, such as vitamin A, vitamin D, vitamin E, etc. The absorption capacity for water-soluble vitamins is poor, such as vitamin B, vitamin C, etc. The skin has a certain ability to absorb certain metal elements, such as lead and mercury. Some cosmetics contain lead and mercury, which can cause poisoning after absorption and accumulation in the skin, resulting in dark spots and rashes, etc.
(iii) Factors affecting the absorption function of the skin The absorption function of the skin is affected by the following factors.
1, the thickness of the stratum corneum the thinner the stratum corneum, the more easily nutrients penetrate and be absorbed. When you do skin care, you can use the de-flaking method to make the stratum corneum thinner.
2, the amount of water content of the skin the more water content of the skin, the stronger the absorption capacity. The use of steam spray surface can supplement the water content of the colloid layer, and the skin is dissolved soft can increase the penetration and absorption ability.
3, the pore state pore expansion, nutrients can reach the dermis through the pores and be absorbed.
4, local skin temperature local skin temperature is high, sweat pores open, nutrients can be absorbed through the sweat pores into the dermis. Skin massage, hot film, steam spray surface, etc. can increase the local temperature to promote the absorption of nutrients.
Seven, the metabolic function of the skin skin cells have the ability to divide and reproduce, renew metabolism
Skin as part of the body, but also involved in the metabolic activities of the whole body. The metabolic function of the skin is most active between 10 p.m. and 2 a.m., during which a good night’s sleep is beneficial for skin care. There is a lot of water and fat in the skin, which not only makes the skin plump and moist, but also provides energy for the whole body’s activities and can replenish the water in the blood or store excess water in the body. The skin is a reservoir of sugar and regulates the concentration of blood sugar to keep it normal.