What is the epidermis?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

The epidermis is the outer layer of the skin and consists of four sub-layers. The stratum corneum, the outer portion of the epidermis, is the outermost layer of the skin. It is the top layer that we can see from the outside and serves as our protective barrier.


The skin areas that are closest to the light above are also known as the layers of the epidermis. The epidermis has a love-hate relationship with the outside world: It pulls in water, heat, and light, and pushes away bacteria, dirt, germs, and toxins.

  • Keratinocytes are the primary players here. These plump cells form at the base of the epidermis and flatten out as they rise to the surface, die, and eventually flake off. Ironically, these dead cells, collectively known as the stratum corneum, make up what we call our skin -- the birthday suit we touch, wash, dry, pamper, and protect (even if we sometimes pierce or tattoo it).
  • Keratinocytes produce keratin, which is the same tough protein that’s in hair and fingernails; on the skin’s surface, it helps form a roadblock against would-be intruders. - - Tough-guy immune system forces called Langerhans’ cells are located here too; they detect foreign substances. More than that, recently these cells have gained greater recognition as extraordinary players in immunity. In late 2005, researchers at Yale School of Medicine demonstrated that Langerhans’ cells in the skin, which had been thought to alert the immune system to invaders, instead dampen the skin’s reaction to infection and inflammation. We now view these cells not just as sentinels or stimulators of immune reactions as previously thought, but more as environmental peacekeepers. The skin is constantly challenged by the environment, but most challenges are not dangerous and do not warrant an immune response. Your Langerhans’ try to keep the peace before warranting a full-fledged response.
  • Melanocytes churn out melanin, which determines the color of your skin, that is, whether you’re dark or pale. It’s the pigment that protects skin from too much ultraviolet light by darkening it after repeated UV exposure, at least in some people. Some types of melanin (Irish-Americans know this all too well) are simply too light to provide any UV protection.

From The Mind-Beauty Connection: 9 Days to Less Stress, Gorgeous Skin, and a Whole New You by Amy Wechsler.

Take the RealAge Test!

Continue Learning about Functions of Skin

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.