corneocyte

Corneocytes are the fully differentiated, anucleate keratinocytes that make up most of the stratum corneum, the outermost layer of the epidermis. They originate from keratinocytes in the stratum basale as these cells migrate through the spinous and granular layers, lose their nuclei and organelles, and become flattened cells filled with keratin filaments. At the end of differentiation they develop a cornified envelope and become embedded in a lipid-rich extracellular matrix that forms the skin’s barrier.

Structurally, corneocytes contain a tightly crosslinked cornified envelope composed of proteins such as involucrin, loricrin, and small proline-rich proteins, which is crosslinked by transglutaminases to provide mechanical resilience. The surrounding intercellular space is rich in lipids delivered by lamellar bodies, contributing to the lipid barrier that reduces transepidermal water loss. Intercellular junctions between corneocytes, called corneodesmosomes, gradually degrade during maturation and desquamation, allowing the outermost cells to shed in a controlled manner.

Functionally, corneocytes form the primary physical barrier of the skin. They help retain moisture, protect against chemical and microbial invasion, and contribute to the mechanical integrity of the epidermis. They also contain natural moisturizing factors generated during protein degradation, which help maintain skin hydration.

Clinical relevance lies in disorders of cornification and barrier function. Abnormal corneocyte formation, desquamation, or filaggrin and lipid processing can lead to conditions such as ichthyosis and atopic dermatitis, reflecting the essential role of corneocytes in skin health.