ABSTRACT
The stratum corneum (SC) is a non-viable layer consisting of corneocytes embedded in a highly ordered lipid matrix. The architecture of the SC therefore is often described as a simplified ‘brick and mortar’ structure with the corneocytes being the bricks and the lipids being the mortar. The extracellular lipid matrix present in the SC is very unique and shows an exceptional three-dimensional ordering of the lipids. The intercellular lipid matrix present in the SC consists of three main lipid classes: ceramides, cholesterol and free fatty acids. Depending on the lipid composition, the lipids adopt an orthorhombic packing, hexagonal packing or liquid packing. The lipids are organized in stacks of lamellae referred to as the lamellar organization. Examining how changes in lipid composition and organization are related to the skin barrier function is often very difficult to study when performing clinical studies.
