The Six Major Physiological Functions of the Skin

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Today, I’d like to introduce the physiological functions of the skin(sources from therapeutique-dermatologique.org).

The physiological functions of the skin are as follows:

It protects the body’s various tissues and organs from external mechanical, physical, chemical, or biological assaults or stimuli to maintain the body’s health.

Its highly developed sensory receptors and nervous conduction system connect external stimuli with the central nervous system, allowing the body to better adapt to various changes in the environment through neural regulation.

It maintains the balance of the entire body and its unity with the external environment.

I. Barrier Function

Normal human skin has two aspects of barrier function:

Firstly, it protects various organs and tissues of the body from mechanical, physical, chemical, and biological harmful factors in the external environment.

Secondly, it prevents the loss of various nutrients, water, electrolytes, and other substances in the tissues.

The broad sense of skin barrier includes: mechanical barrier, physical barrier, chemical barrier, biological barrier, and pigment barrier, etc.

Mechanical barrier: It mainly refers to the protective ability against mechanical stimuli such as friction, pulling, squeezing, and impact.

Physical barrier: It mainly prevents the loss of body water, electrolytes, and nutrients, inhibits the invasion of external substances, and achieves protective effects. The physical barrier also includes defense against various environmental radiations. For example: the skin is a poor conductor of electricity (mainly the stratum corneum, the dermis, and subcutaneous tissue are good conductors of electricity), normal skin can absorb light (the shorter the wavelength, the shallower the penetration into the skin, and most of the ultraviolet rays are absorbed by the epidermis), absorbs electromagnetic waves (magnetic waves can produce certain magnetic biological effects on human tissues).

Chemical barrier: The normal pH of the skin is about 5.5-7.0, weakly acidic, which has a buffering effect on alkaline and acidic substances.

Biological barrier: The skin surface has a rich symbiotic microbial population, which can prevent the invasion of pathogenic and harmful organisms.

Pigment barrier: Mainly melanin and skin pigmentation can protect the body from damage caused by solar radiation.

II. Absorption Function

The skin mainly absorbs external substances through four pathways: the stratum corneum, hair follicles, sebaceous glands, and sweat gland ducts. Among them, the stratum corneum is the most important pathway. The substances enter the skin from the epidermis can be divided into three stages:

Transdermal penetration, that is, entering the dermis through the epidermis.

Skin absorption, entering the systemic circulation through the vessels in the dermis.

Accumulation at the site of action.

III. Respiratory Function

Except for some special sites with a thickness of more than 1mm, the epidermis can obtain all the oxygen it needs through diffusion from the skin surface. The proportion of skin respiration to the total respiratory volume of the human body: oxygen absorption is less than 1%-1.9%, and carbon dioxide excretion is 2.7%.

IV. Excretory Function

The skin has secretion and excretion functions, mainly through sweat glands (secreting and excreting sweat) and sebaceous glands (secreting and excreting sebum).

V. Temperature Regulation Function

Body temperature is a necessary condition for metabolism and normal life activities of the body, including surface temperature (skin, subcutaneous tissue, and muscles, etc.) and deep temperature (heart, lungs, brain, and abdominal viscera, etc.).

When the environmental temperature is 23°C, the skin temperature of the feet is 27°C, the skin temperature of the hands is 30°C, the trunk temperature is 32°C, and the forehead temperature is 33-34°C (the temperature of the limbs is the lowest, and the closer to the trunk and head, the higher the skin temperature).

Three ways to regulate body temperature:

Regulate skin vascular responses and sweat gland secretion through the sympathetic nervous system.

Change the activity of skeletal muscles through the somatic nervous system, such as shivering in cold environments.

Regulate the metabolic rate of the body by changing the secretion activity of the thyroid and adrenal medulla(quotes from therapeutique-dermatologique).

VI. Sensory Function

It mainly includes six basic sensations: touch, pressure, cold, warmth, pain, and itch.

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