noun, plural: cornifications
The process of forming a keratinized, horny layer of epidermis
Made to become, converted into, or forming a horny layer of epidermis
Cornification is a process wherein a horny layer of epidermis is formed and acts as an epidermal barrier. It is characterized by the production of keratin. Keratins are a group of fibrous proteins made up of coiled polypeptide chains. These polypeptide chains combine forming supercoils. Keratins are important structural component of biological structures such as skin, hair, horn, nails, feathers, hooves, etc. Apart from the production of keratin, cornification is also characterized by the production of small proline-rich proteins and transglutaminase. The result is a formation of a cornified cell envelope underneath the plasma membrane. During the last stages of cornification, the cells lose the organelles including the nuclei and become filled by keratin. This then leads to the cessation of metabolism. Eventually, the fully keratinized cells go through a programmed cell death.
Cells that underwent cornification, particularly the epidermal cells, become almost waterproof on the outermost of the skin. The result is a strong yet elastic epidermal barrier. A continuous rubbing and pressure of the cornified layer leads to further thickening and the formation of calluses. Calluses though may disappear when pressure is removed since the epidermal cells are constantly shed and replaced.