WHAT QUALITY IS NOTABLE IN THE STRATAM CORNEMUM?
The stratum corneum (SC) is a layer of dead epidermis cells that protects the skin from physical insults, reduces trans-epidermal water loss and provides an effective barrier against pathogens. The SC is a complex mixture of highly ordered multilamellar lipid sheets that are interlinked by cross-linked keratin filaments. The structure of the SC is an integral part of the skin’s innate defense mechanisms against environmental stressors, including oxidative and UV damage, mechanical injury and chemical exposure, as well as inflammatory diseases such as atopic dermatitis and psoriasis.
During the keratinization process, keratinocytes encapsulate themselves with a protective lipid secretory product called ceramides. The lipids are composed of fatty acids that form highly polar head groups with the lipid bilayer, giving them a strong hydrophobic property. Additionally, the lipids are tethered together by cross-linking proteins, which create a brick wall-like structure in the SC.
When the lipid bilayer in the SC is disrupted, such as by excessive dryness and a lack of hydration, the proteins become fragile, the keratin filaments disperse, and the squames lose their adherence to one another. The result is a decrease in the thickness of the SC and an increase in TEWL.
The loss of a strong barrier in the skin results in the penetration of allergens and other molecules into the dermis, causing inflammation that is visible as redness, itching, burning, and scaling. This systemic response may eventually trigger autoimmune diseases such as atopic dermatitis, psoriasis and other inflammatory conditions.