Corneocyten

Corneocytes are the primary cells that make up the stratum corneum, the outermost layer of the epidermis in the skin. They are terminally differentiated keratinocytes, meaning they have completed their development and are no longer actively dividing or metabolizing. Corneocytes are flattened, anucleated (lacking a nucleus), and dehydrated cells that are filled with a protein called keratin. This keratin provides structural integrity and a barrier function to the skin.

The formation of corneocytes, a process known as cornification or keratinization, is a crucial aspect of skin biology. It begins with keratinocytes in the basal layer of the epidermis, which proliferate and move towards the surface. As they ascend, they undergo significant changes in their internal structure and composition. They lose their organelles, flatten out, and accumulate keratin. Simultaneously, a lipid envelope forms around the cell, contributing to the barrier properties of the stratum corneum.

The stratum corneum, composed of layers of corneocytes embedded in a lipid matrix, acts as a protective shield against mechanical stress, UV radiation, and the invasion of microorganisms. It also plays a vital role in preventing transepidermal water loss, thereby maintaining skin hydration. Corneocytes are continuously shed from the surface of the skin in a process called desquamation, which is balanced by the continuous production of new cells from the basal layer. This renewal process is essential for maintaining skin health and function. Abnormalities in corneocyte formation or desquamation can lead to various skin conditions, such as psoriasis and ichthyosis.