A Guide to Your Skin’s Epidermal Layer
Your skin protects your internal organs, nerves, muscles and blood vessels from damage. Skin is made up of three layers: the epidermis, the thin outer layer; dermis, the thick middle layer; and hypodermis, the innermost layer.
This blog will focus on the outermost layer, the epidermis. Your epidermis protects you from the harmful effects of sunlight, bacteria and environmental toxins. The epidermis is also responsible for the look and health of your skin.
The epidermis has four layers that perform different functions:
1. Stratum basale. This is the deepest layer of the epidermis, and it’s responsible for renewing the skin. This layer is mostly comprised of keratinocytes. Keratinocytes produce keratin, the protein that protects your skin from chemical products and bacteria. Keratinocytes slowly migrate from the basal layer up toward your skin’s surface, dividing and changing as they go.
Melanocytes are also found in the basal layer. Melanocytes produce melanin, the pigment that gives skin and eyes their color. Melanin filters out ultraviolet radiation from the sun, protecting your skin from skin cancer and premature aging. Chronic exposure to light increases the number of melanocytes, so you have more on your face than your lower back, and more on your outer arm than your inner arm. Areas with fewer melanocytes (and therefore less melanin) are more vulnerable to sun damage, so don’t forget to apply sunscreen to those spots.
2. Stratum spinosum. Langerhans cells, which are part of your skin’s immune system, are located in this layer. Langerhans cells detect foreign substances and help prevent infection. They’re also involved in the development of allergies.
3. Stratum granulosum. Keratin and waterproofing lipids are produced and organized in this layer.
4. Stratum corneum. This outermost layer of the epidermis contains many cornified or horn-like keratinocytes. The stratum corneum is relatively waterproof and prevents most bacteria, viruses and other foreign substances from entering the body. This outermost layer of dead skin cells is constantly being shed. The movement of epidermal cells from the basal layer up to the top layer takes about 28 days, so your skin cells replace themselves monthly.
The stratum corneum is much thicker on body parts that require extra protection, such as the palms of your hands and soles of your feet. Your epidermis ranges in thickness from .05 mm on your eyelids to 0.8-1.5 mm on the palms of your hands and soles of your feet.
Skin’s Epidermal Layer
Lipids in this outermost layer maintain a moist, pliable skin barrier. Ceramide, a lipid, surrounds skin cells and prevents water from leaving your skin. After the age of 40, there is a sharp decline in skin lipids, so you may develop dry skin as you age.
How does micro-needling interact with the epidermis?
Cosmetic micro-needling uses short needles to create micro-channels through the epidermis. When your epidermis is mechanically disrupted by the micro-needles, the cells are simply “pushed aside,” and the body’s reaction only seeks to “reseal” the channels and increase epidermal cell turnover temporarily (due to the excretion of growth factors in blood serum released via disrupted capillaries). This leads to a rejuvenation of the outer layer without unwanted effects such as pigmentation issues or scar tissue formation. Cosmetic micro-needling with SkinPen can help to reduce the appearance of wrinkles and fine lines and improve the appearance of aging skin.