The stratum corneum (
Latin for 'horny layer') is the outermost layer of the epidermis. The
human stratum corneum comprises several levels of flattened corneocytes that are divided into
two layers: the stratum disjunctum and stratum compactum. The stratum disjunctum is the uppermost and loosest layer of
skin. The stratum compactum is the comparatively deeper, more compacted and more cohesive part of the stratum corneum. The corneocytes of the stratum disjunctum are larger, more rigid and more hydrophobic than that of the stratum compactum.
The stratum corneum is the dead
tissue that performs protective and adaptive physiological functions including mechanical shear, impact resistance,
water flux and hydration regulation, microbial proliferation and invasion regulation, initiation of inflammation through cytokine activation and dendritic
cell activity, and selective permeability to exclude toxins, irritants, and allergens. This layer is composed of
15–20 layers of flattened cells with no nuclei and cell organelles. Their cytoplasm shows filamentous keratin. These corneocytes are embedded in a lipid
matrix composed of ceramides, cholesterol, and fatty acids.
