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Corneocytes, also known as horny cells, are the terminally differentiated cells of the epidermis. They are formed from keratinocytes, which are the primary cells of the epidermis, as they migrate towards the surface of the skin. During this migration, keratinocytes undergo a process of keratinization, during which they accumulate keratin, a tough structural protein, and lose their internal organelles such as the nucleus and mitochondria. This process results in the formation of a flattened, anucleated, and dehydrated cell filled with keratin.

These dead, flattened cells are then arranged in layers, forming the stratum corneum, the outermost layer of the epidermis. The stratum corneum serves as a crucial barrier against mechanical stress, chemical insults, and the invasion of microorganisms. Corneocytes are held together by a lipid matrix, which further contributes to the barrier function of the skin.

The shedding of corneocytes, a process known as desquamation, is a continuous and essential part of skin renewal. This shedding typically occurs every 2 to 4 weeks. As new corneocytes are formed and pushed upwards, the older ones at the surface detach and are shed. This natural turnover process helps to maintain the integrity of the skin barrier and prevent the accumulation of damaged cells. Disorders of desquamation can lead to various skin conditions, such as dryness, scaling, and certain dermatological diseases.