The structural basis of the skin barrier is the formation of the most superficial keratinocytescuticle, KeratinocyticlipidNatural protective factor, which is mainly used to prevent the loss of water and electrolyte in the body, prevent the invasion of external environment, and help maintain the homeostasis of the body.[1]
Chinese name
Skin barrier function
Foreign name
Skin barrier function
Features
Prevent water loss and external environment damage
Keratinocytes undergo mitosis, differentiation, degeneration and disappearanceAcanthocyte layer、Granulosa cellThe stratum corneum eventually becomes the outermost stratum corneum of the epidermis, forming its unique multi-layer structure.Keratinocytes "stack" in the continuous matrix of intercellular lipids, forming a classic "brick wall" structural system.
stayEpidermal cellDuring the migration from the basal layer to the stratum corneum, the lipid content was also changing.In the granular layer, lipids are contained in the intercellular lamellar bodies. When cells move to the stratum corneum, lipids are squeezed into the intercellular space and form a lipid bimolecular structure with the keratinocytes.Hydrophobic lipids outside the cuticle cells prevent water loss and regulate the movement of electrolytes in the cuticle.
3. Keratinization capsule
The normal gene coding expression of keratinization envelope component protein can make the epidermis normal stratification and keratinization.[1-2]
Moderating factor
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onecalcium ionThe relative concentration of ions inside and outside the capsule of keratinocytes (i.e., the polarity of the capsule) plays an important role in the process of barrier repair.The intracellular free calcium concentration is about 100 nmol/L, and the extracellular calcium concentration is about 1~3 nmol/L. The maintenance of the concentration difference between intracellular and extracellular ions is mainly maintained by ion related channels.Calcium ion induces differentiation and proliferation of keratinocytes into the stratum corneum, formation of keratinized sheath and epidermal lipid synthesis.
twoenzyme: The animals, plants and microorganisms we contact in the external environment can produce or contain protease.From the genetic point of view, environmental proteases and endogenous proteases lead to the loss or damage of skin barrier function, which increases the sensitivity of the body to allergens and further worsens allergic diseases.[2]
Barrier function
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1. Transdermal water loss barrier（TEWL）: Various internal and external factors will affect the skin penetration barrier, such as climate, body pressure and many skin and system diseases.The stratum corneum is the product of epidermal terminal differentiation, which has the function of protecting the body. The most important one is the permeability barrier, which blocks the loss of water evaporated through the skin.TEWL reflects the amount of water evaporated from the skin surface, so it is an important index to evaluate the skin function.
2. Antimicrobial and immune barrier: healthy skin surface is also covered with many microorganisms, but the human body will not be infected.However, studies have shown that in the natural skin defense system, keratinocytes act asEffector cellAnd then produce antibacterial peptide substances to inhibit the growth of microorganisms on the skin surface.[3]
