Skin Remodeling Lesson 1: Skin Structure and Function

This entire E-course is intended for informational purposes only and does not replace medical advice. Please consult our warning page before using aggressive measure like chemical peels or skin needling.

In order to understand the remodeling techniques described in this E-course, you’ll need to know a little bit about skin structure. There’s no need to get overly detailed; the following descriptions should give you enough information to understand the commonly used skin terms.

The Epidermis

The epidermis is the outer layer of the skin. The condition of the epidermis will determine how “fresh” your skin appears and how well it absorbs and holds moisture. It is rather thin compared to the deeper layers of the skin, and gets even thinner as we age.

Your epidermis is composed mainly of keratinocytes, the primary type of skin cell, which form in the lower layers of the epidermis and move upwards as they age. This upward movement and cell replacement is called cellular turnover. It healthy skin, a keratinocyte will take about a month to move upward though the epidermal layers and eventually be shed. Cellular turnover slows as we age, leading to irregularities in the epidermis and dull looking skin.

Another specialized cell in the epidermis is the melanocyte. This type of cell produces melanin, the pigment that determines your skin color. When melanocytes are damaged from age, injury, sun exposure, or hormone irregularities they can begin producing too much melanin, leading to discoloration in the form of dark spots. Sun spots, age spots, melasma or darkened scar tissue are common forms of discoloration that can be treated with the right combination of skin care products.

There are four layers in the epidermis. The uppermost layer called the stratum corneum is of great concern in skin care. The stratum corneum is composed of 10 to 30 layers of dead keratinocytes, which are now called corneocytes. The corneocytes are surrounded by proteins that retain water. Each layer can hold 3 times its weight in water and makes the skin pliable. When the moisture content drops too low, the skin becomes dry and cracked. Eventually the corneocytes slough off the surface, completing the natural cycle of a skin cell. The shedding of dead skin cells is known as exfoliation, a term that describes the natural process as well as the skin care technique.

Another important part of the stratum corneum is the skin barrier, a protective mix of lipids, cholesterol, and ceramides that help retain skin moisture. An intact, moist stratum corneum is very important to skin health because it functions as a barrier between your live skin and the outside elements that can damage it.

This barrier function of the stratum corneum is very important, but can be problematic when you are trying to use topical skin care products to remodel skin damage. Sometimes, the natural exfoliation process is slowed down and non-functioning corneocytes adhere to the surface of the stratum corneum. This is very common in dry and aging skin, but can happen even with healthy skin. The unnecessary layer of dead skin can prevent your products from being properly absorbed and reaching live skin tissue. Even a normal stratum corneum can impede absorption, especially if it is dry. Delivering active ingredients through the stratum corneum to live epidermal tissue while maintaining a functional skin barrier is one of the most important parts of a skin care regimen.

The Dermis

The dermis is the thicker layer of skin that lies below the epidermis. The dermis contains sweat and sebaceous glands, nerves, hair follicles, blood vessels, lymph nodes, and, most importantly in skin care, the skin matrix. The skin matrix is a mesh like structure composed of primarily collagen, which makes up the bulk of dermal tissue, and elastin, which is responsible for skin tightness and elasticity, along with other proteins and polymers needed for skin health. These components are produced by specialized structures in the dermis called fibroblasts.

The condition of your skin matrix determines your skin’s toughness and elasticity. Most skin damage is the result of irregularities in the skin matrix, including wrinkles, scars, and stretch marks. In young healthy skin, bundles of collagen and elastin fibers are evenly distributed and provide optimal strength and flexibility. New fibers are constantly being synthesized by fibroblasts and enzymes break down old or damaged tissue. But sometimes, this cycle of regeneration gets out of balance. As we get older, matrix synthesis slows and degradation picks up, causing a loss in the overall amount of healthy collagen and elastin. The skin matrix starts to warp and irregularities appear in the mesh.

Damage like scars and stretch marks are not related to aging, but are caused by a similar process. When the matrix is injured, it can’t always heal with the same structure that it had before. In its haste to seal the skin and restore the barrier, the wound is repaired with an irregular shaped matrix with a different mix of components. The collagen production process can go into overdrive in some scars, resulting in hardened, raised tissue. In stretch marks, the entire dermis can be torn through, often leaving an absence of collagen or any matrix whatsoever.

In order to treat most skin damage, the treatment must reach or stimulate the dermis. Active ingredients pass from the epidermis through a complex structure between the two layers called the dermoepidermal junction or basement membrane. Some resurfacing techniques deliver controlled damage into the dermis to stimulate matrix synthesis.