SKIN Physiology

Human skin is not only a mere body covering but an organ with many important functions for human life.

The skin has the following functions:

– Guard

– Thermostat

– Metabolism

– Excrete

– Acquire feeling

Keratin (keratin) and pigment (melanin)

– Immunity

– Create appearance and race

1. Protection function

Skin is a protective barrier, protecting organs such as nerves, blood vessels, muscles, bones, and internal organs from being attacked by harmful biological, mechanical, chemical and physical factors.

Due to the constantly differentiated structure of the epidermal cell layers, the parasitic bacteria on the skin are always repelled and eliminated to the outermost of the keratinocytes. In addition, thanks to the tight structure of the Malpighi layer, there are glue and connective fibers that make the skin elastic and supple, so the skin can withstand the pressure of the environment against external injuries. prevent bacteria from entering the body.

The stratum corneum has the effect of preventing light with a wavelength of 200 nm from penetrating the skin and the dermis prevents light radiation with a wavelength of 340-700 nm from reaching the dermis.

2. Thermostat function

Skin regulates temperature, keeping body temperature at a constant level by two mechanisms: sweating and vasomotor response.

When the body temperature rises due to an infection, the ambient temperature rises or for some other reason, the body responds by dilating blood vessels under the skin to increase heat loss, sweat glands increase secretion. increase evapotranspiration to reduce heat

When the temperature drops, the blood vessels under the skin will constrict, reducing heat loss on the skin.

3. Excretory function

3.1 Excretion of sweat

The number of sweat glands varies according to different body regions. There are 620 glands/cm2 of skin on the palms of the hands and feet, and 120 glands/cm2 of skin in the thighs. The entire body has 2.5 million sweat glands.

Different body regions excrete different amounts of sweat. My body ensures to excrete 50% of the amount of sweat. Two lower limbs 25%, 2 upper limbs and head 25%.

In addition to participating in temperature regulation, sweat also has the effect of eliminating waste products, toxic to the body.

The composition of sweat consists of: 99% water, 1% electrolytes (NaCl, Potassium, Calcium), urea, ammonia, …

3.2 Excretion of sebum

The skin is always excreting sebum. Sebum makes the skin waterproof, prevents water evaporation, makes the skin soft, fights bacteria and fungi.

The composition of the residue: 2/3 is water, 1/3 is fatty acids, triglycerides, cholesterol, sterols, phospholipids, vitamin E

If the sebum secretion is reduced, it will make the skin rough and easy to scab. But if you excrete too much sebum, it will make your skin oily, enlarged pores, and more acne.


4. Metabolic function

The skin holds 9% of the body’s water and contains the most NaCl in the body, so the skin plays an important role in the water and electrolyte balance system.

Under the effect of ultraviolet rays, cholesterol under the skin is converted into vitamin D – a vitamin necessary for calcium absorption in the bones. Not only that, the skin is also involved in the metabolism of protein, sugar, and fat.

5. Sensory acquisition function

The sense of touch and touch is detected by Messner and Pacini corpuscles. These corpuscles are unevenly distributed throughout the body, most concentrated in the palms. Reception of the feeling of pressure are Golgi and Mazzoni particles.

The sensation of heat is received by Rufini corpuscles. Cold sensation is received by Krause corpuscles in the dermis. The whole skin has 30,000 hot spots, 250,000 cold spots. The most sensitive areas to heat and cold are the chest, abdomen, nose, and ears.

Pain is felt by nerve endings. The ability to perceive pain is generally asymmetrical in the body. Some people have the right side of the body more sensitive to pain than the left side, and vice versa.

Feeling itchy: when people have an itch, they tend to want to scratch because scratching will destroy cells, releasing histamine. Histamine secretion will relieve itching, but when secreted too much will increase the itch and become a vicious cycle the more you scratch, the more it itch.

6. Immune Function

In the skin, there are many immune competent cells such as Langerhans cells, T lymphocytes. When an antigen penetrates the skin, Langerhans cells appear to capture antigens and present antigens to competent Lymphocytes. immunity rights.

7. Appearance and race creation function

Different races have different skin colors. Human skin contributes to the shape of each of us.

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