The protective barrier that our skin produces is a kind of shield that protects our body from the negative effects of external factors. Damage to its structure can lead to various inflammations and diseases, even atopic dermatitis (AD). Which skin layer actually performs the barrier function?
All skin layers and their functions
Skin is the body’s largest organ. Its main function is to protect the internal organs from external threats. Adult skin covers an area of 1.5 to 2m2 and, including the subcutaneous tissue, can weigh up to 20 kg.
Human skin is composed of three layers: epidermis, dermis and subcutaneous tissue. The epidermis has the most important function in building a protective barrier. It is the outermost structure of the human body and consists of five layers. The epidermis is responsible for protection against UV radiation, temperature, chemicals, damage or pathogenic microorganisms. The epidermis is responsible for the skin’s color, as it contains melanocytes, or pigment cells. They directly protect the body against UV rays. The Langerhans cells, which are also found in the outer layer of the skin, are responsible for regulating immune responses. In simple terms, they recognize pathogens entering through the epidermis and transmit the appropriate information to the antigens.
The epidermis also has its layers, the first of which is the stratum corneum. It can be compared to a wall, which on the joints is filled with mortar. The building material in the epidermis are corneocytes – dead cells of the epidermis. One can easily guess that since they are dead, they will soon undergo exfoliation. On the other hand, the mortar is lipids, or fatty components, which in its composition have ceramides. And here we come to the barrier that protects the skin from the harmful effects of microorganisms – the hydrolipid coat present on the top layer of the stratum corneum.
Defensive functions support the acid reaction of the skin, which protects it from harmful microorganisms.
The epidermis has another important function – it is responsible for permeability control and selective transport. But what does this mean in practice?
The epidermis, thanks to its structure, does not allow all substances from the environment to enter the skin. In addition, it regulates the level of hydration, that is, it prevents transepidermal water loss.
Human immune system
The skin is the organ that is most exposed to the constant action of environmental factors and antigens. It is the immune system located in the first layer of the skin. It is responsible for identifying the threat and eliminating it.
In the first line of defense stands the epidermis, which in addition to an acidic pH also has to help the bacterial flora that is located on its surface. Sometimes the pathogen will break through the epidermis, then it is the more advanced cells of the defense system that begin their work. They can trigger an acute defensive reaction that will result in, for example, acute inflammation of the skin or even the body.
What is the microbiome?
Every person has a different microbiome, which changes with age. Simplifying, these are various types of microorganisms that live in symbiosis with our skin. They include, for example, fungi, bacteria or viruses. It is important that the balance between good and bad microorganisms is maintained. Then our skin is healthy and its protective shield works properly. However, if this balance is disturbed, various diseases can appear on the surface of the skin. The most important function of the microbiome is to adequately protect the microflora on the surface of the skin, maintain the proper pH and strengthen the immune barrier. All these functions affect the proper functioning of the skin barrier.
And it consists of – the hydrolipid coat with the epidermis, the microbiome and the immune system.
It is worth remembering that only if these three elements work properly, the human body is properly protected against pathogens. Proper external care, but also internal, affect the condition and health of the skin. Therefore, you should drink plenty of water rich in minerals and use creams and preparations selected for your skin type. It is also very important to protect the skin against UV rays. Such prevention will allow you to enjoy a beautiful appearance for many years.
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