Skin: The "super shield" that protects the human body

Author: Mao Chong Sichuan Provincial People's Hospital

Reviewer: Yang Jianing, Chief Physician, Sichuan Provincial People's Hospital

Skin is like our body's "super shield", always protecting our body from wind and rain and fighting against enemies.

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1. Structural basis of the skin

From the perspective of the microscopic "small world", the skin is composed of three main layers.

——The outermost layer of the epidermis is like a solid wall composed of a group of well-trained "keratin soldiers". These keratinocytes continuously move upward and differentiate from the basal layer, and finally form the "iron wall" of the stratum corneum. It is not so easy for the external physical friction, chemical stimulation, and mischievous microorganisms to break through this defense line!

——The middle layer of the dermis is like a super complex "processing plant" and "nutrition bank". The collagen and elastic fibers in it are like crisscrossed "reinforced concrete", which give the skin elasticity and toughness, allowing our skin to return to its original shape after stretching. In addition, the dermis contains "plumbers" such as blood vessels, nerves, and lymphatic vessels, as well as the roots of various skin appendages such as hair follicles and sweat glands, which work together to provide sufficient nutrition and express signals for the metabolism of the skin.

——The subcutaneous tissue is like a soft "cushion" and is mainly composed of fat cells. These fat cells can store energy and keep warm. When there is an external force impact, they will stand up and protect the internal bones and organs.

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2. Skin's defensive function

The skin is the body's barrier against external aggression. It is like a super strict "security inspector" that prevents most pathogens, such as bacteria, viruses and fungi, from entering the human body.

The cells of the stratum corneum are closely arranged, like guards holding hands. Coupled with the acidic environment on the surface (pH value is about 5.5), it is difficult for pathogens to "set up camp" here! The sebum secreted by the skin contains antibacterial substances such as fatty acids, which can directly defeat certain microorganisms or make them "dare not act rashly". In addition, the normal flora of the skin is like a group of "local residents". They form a stable "small society" on the surface of the skin, "compete for territory" and "grab food" with those pathogens, and help maintain the health of the skin.

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3. Sensory functions of the skin

The skin is also a super-sensitive "sensory elf" with abundant sensory nerve endings. When we touch an object lightly, the tactile bodies in the skin can sense the pressure and tactile stimulation, and then transmit these signals to the brain, allowing us to distinguish the texture and shape of the object.

When the "naughty ghost" of the ambient temperature changes, the cold receptors and warm receptors on the skin will react quickly like a thermometer to let us know the cold and hot. If the skin is bullied by "bad guys" such as needle pricks or burns, the pain receptors will act like a "small trumpet" and immediately transmit pain signals to the brain, so that we can quickly make an avoidance reaction to avoid further damage.

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4. The regulatory function of the skin

The skin is a great contributor to body temperature regulation. When the external temperature rises, the blood vessels in the skin expand, the blood volume increases, and the heat in the body is brought to the surface of the body for dissipation. At the same time, the sweat glands secrete sweat, which takes away a lot of heat during evaporation, lowering the body temperature.

When the external temperature drops, the blood vessels in the skin contract to reduce heat loss. At the same time, the arrector pili muscles contract to form a relatively static air layer on the skin surface, just like covering the skin with a "small quilt" to keep it warm.

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5. The skin’s self-repair ability

Although the skin faces various injuries every day, it has a strong ability to repair itself. When the skin is slightly scratched or cut, the cells around the wound will quickly proliferate and migrate to form new tissue to fill the wound.

At the same time, the body will sound the "alarm" - starting an inflammatory response, releasing various growth factors and cytokines to promote wound healing. In this process, collagen synthesis increases, and new blood vessels grow to the wound area to provide nutrients and oxygen for repair.

In short, the skin, the "super shield" of the human body, silently protects our health and life with its diverse structure and powerful functions. We must not mistreat it, and try to avoid damage to it caused by excessive sun exposure, bad eating habits and unreasonable skin care methods!