Stratum corneum keratin and intercellular matrix (SC)

The stratum corneum (SC) is the outermost layer of the epidermis and serves as the primary physical and chemical barrier of the human body (Source 1.1.5). It is structurally organized according to a "brick-and-mortar" model, where protein-rich corneocytes (the bricks) are embedded in a lipid-rich intercellular matrix (the mortar) (Source 1.1.2, 1.3.4). The corneocytes are filled with a dense network of keratin intermediate filaments, while the intercellular matrix consists of a highly organized lamellar structure of ceramides, cholesterol, and free fatty acids (Source 1.1.1, 1.1.3, 1.3.3). This complex is essential for maintaining homeostasis by preventing excessive transepidermal water loss and protecting against exogenous irritants and pathogens (Source 1.1.2, 1.2.2). In dermatological conditions such as atopic dermatitis, psoriasis, and ichthyosis, the integrity of either the keratin filaments or the lipid matrix is compromised, leading to barrier dysfunction and inflammation (Source 1.1.5, 1.2.2, 1.3.5). Consequently, the SC is a major therapeutic target for topical agents, including keratolytics like salicylic acid that reduce corneocyte cohesion and emollients that replenish deficient lipids to restore barrier function (Source 1.3.1, 1.3.3). Additionally, the SC represents the rate-limiting barrier for transdermal drug delivery, often requiring chemical enhancers to temporarily disrupt the lipid organization for systemic absorption (Source 1.3.1, 1.3.2).

Other names

Skin barrierHorny layerCorneocyte-lipid matrixBrick-and-mortar systemEpidermal barrier

Keratolysis (dissolution of intercellular cement and keratin), Barrier restoration (exogenous lipid replenishment), Humectancy (water binding within corneocytes), and Penetration enhancement (disruption of lipid lamellar organization).