facettskikt

Facettskikt, also known as the epidermis in humans, is the outermost layer of the skin that serves as a protective barrier against environmental damage, pathogens, and dehydration. In dermatology and biology, the term "facettskikt" is primarily used in Scandinavian languages, particularly in Norwegian, Danish, and Swedish. This layer is composed of stratified squamous epithelium, meaning it consists of multiple layers of cells that flatten as they move toward the surface.

The epidermis itself is not vascularized, relying instead on nutrients and oxygen diffusing from the underlying dermis. It is primarily composed of keratinocytes, which produce the fibrous protein keratin, giving the skin its protective properties. The outermost layer, known as the stratum corneum, consists of dead, flattened keratinocytes that continuously shed and are replaced by cells from deeper layers. This process, called keratinization, ensures the skin remains resilient and functional.

In addition to keratinocytes, the epidermis contains other cell types, including melanocytes, which produce melanin—the pigment responsible for skin color—and Langerhans cells, which play a role in immune defense. The thickness of the epidermis varies across the body, being thicker on areas like the palms and soles and thinner on regions such as the eyelids.

Damage to the facettskikt, such as burns, cuts, or chronic conditions like eczema, can impair its protective function, leading to increased susceptibility to infections and fluid loss. Proper skincare, including hydration and sun protection, helps maintain its integrity and overall skin health. The study of the epidermis and its functions is essential in fields like dermatology, cosmetology, and medical research.