corneocytes

Corneocytes are the highly specialized, terminally differentiated keratinocytes that form the outermost layer of the skin, the stratum corneum. They are anucleate and flattened cells that arise from basal keratinocytes as they move upward through the epidermal layers. During maturation, corneocytes undergo cornification, losing nuclei and organelles and developing a robust, cross-linked protein envelope that encases a network of keratin filaments.

Key components include a cornified envelope composed of proteins such as loricrin, involucrin, and small proline-rich proteins, which provides mechanical strength. Keratin intermediate filaments within the cells contribute to their structural integrity. Filaggrin, produced in earlier layers, is degraded to release natural moisturizing factor (NMF) components, helping to maintain skin hydration. The intercellular spaces of the stratum corneum are filled with extracellular lipids—ceramides, cholesterol, and free fatty acids—delivered by lamellar bodies, forming lipid lamellae that reinforce the barrier.

Functionally, corneocytes and the surrounding lipid matrix create the primary barrier of the skin, restricting transepidermal water loss and protecting against environmental agents and pathogens. Desquamation, the orderly shedding of corneocytes, completes the turnover of the stratum corneum.

Clinical relevance is linked to barrier function: defects in corneocyte formation, envelope cross-linking, or lipid processing can contribute to conditions such as ichthyosis and atopic dermatitis. Research methods, including tape-stripping, are used to study corneocyte cohesion and maturation in health and disease.