The Human Skin Demystified
How well do you know your skin?
The skin is the largest organ of the human body and certainly one of the most important. It protects our body from external attacks. With the sense of touch, it makes us feel cold, warm and soft caresses. Our skin puts us in contact with our environment, it communicates all sorts of emotions to us and to others. Just as our eyes are the mirror of our soul, our skin is the reflection of ourselves. It is therefore not surprising that everyone wants to keep it beautiful, healthy and youthful looking for as long as possible, even throughout their lives.
With this in mind, it is good to know how the skin is constructed, how it functions and how it ages in order to make the right choices to keep it healthy. The skin is made up of several superimposed layers of skin tissue, including the epidermis on the surface, the dermis in the center and the hypodermis located deeper. Each of these layers of skin tissue is in turn composed of cells with different properties that are continually regenerating to ensure the maintenance of the barrier function that protects our body from the external environment.
The surface layer of the skin, the epidermis, is itself made up of four successive layers: the basal layer located at the junction of the dermis, followed by the spinous layer, the granular layer and finally the horny layer on the surface. In the basal layer, at the base of the epidermis, keratinocytes are born and gradually migrate to the surface of the skin to produce keratin, a fibrous, water-insoluble protein, as well as various lipids that give the skin its impermeability.
At the point of contact between the epidermis and the dermis, just below the basal layer, we find the dermal-epidermal junction (DEJ), also called the basal lamina. It is a membrane formed by small protuberances called dermal papillae. These papillae are like small corrugations that intertwine the epidermis with the dermis and vice versa. On the upper side of the EDD, the dermal papillae provide oxygen and nutrients to the keratinocytes in the epidermis while allowing them to eliminate their waste products, while on the lower side, the membrane traps the collagen and elastin fibers in the dermis.
Collagen and elastin in the dermis are protein fibers derived from fibroblasts, the main cells of the skin. While collagen fibers give the skin its resistance to deformation and traction, elastin gives it its elastic properties.
Finally, we should mention the glycosaminoglycans (GAGs) that are also found in the dermal layer. These are carbohydrate macromolecules whose one of the properties is to retain water. Therefore, GAGs are essential for the hydration of the skin. Moreover, hyaluronic acid, which is found in many cosmetic products, is a type of glycosaminoglycan whose function is to maintain good hydration of the dermis and, by the same token, to increase its firmness. In addition, GAGs interact with collagen fibers to ensure optimal orientation, which also contributes to good dermal stability and skin firmness.
How exactly does the skin age?
Skin aging is a gradual and continuous phenomenon over time. It is a complex biological process induced by a combination of factors specific to our genetics and the environment in which we live.
As the years go by, our skin cells renew themselves less quickly and less efficiently. As well, our skin is subjected to various aggressions from the outside environment, including the sun, air pollution, cold and wind, not to mention the inevitable injuries of life, such as scratches, cuts and other scrapes that leave scars. All of these factors combined contribute to the aging of our skin and cause it to become thinner and more fragile, so that the first wrinkles and fine lines often appear in our 30s.
More specifically, with age and the slowing down of cellular regeneration, the dermal-epidermal junction flattens out because the dermal papillae gradually lose the network of proteins necessary to maintain them. This flattening reduces the exchange surface between the various layers of the skin, resulting in a loss of the dermis’ capacity to nourish the epidermis and to rid it of its metabolic waste products.
As a result, the layers of keratinocytes are less numerous and of poorer quality. Keratin synthesis is then reduced, causing thinning of the epidermis, loss of its radiance and softness. As for the fibroblast population of the dermis, it is reduced by half between the ages of 20 and 80, breaking the balance between the synthesis, maturation and degradation of collagen and elastin. From the age of 20, collagen production slows down. From the age of 30, the skin loses up to 1.5% of its collagen per year and this loss increases with time to reach 50% at age 50, and even a 75% decrease at the end of its life. The synthesis of glycosaminoglycans (GAGs) is also considerably reduced, which greatly affects skin hydration and explains the frequent occurrence of skin dryness in adults as they age. This loss of hydration is detrimental to the proper stability of the dermis and the firmness of the skin.
In short, our skin is an extraordinary organ. Like starfish, it also has an incredible ability to regenerate itself, but this ability diminishes with the passing years. As an adult, our skin needs a helping hand to slow down its premature aging and promote its renewal. Fortunately, with L’ÉTOILE COSMÉTIQUES, it’s never too late or too early to take care of your skin and help it regain its radiance!
