The largest organ of the human body is the skin. It defends the soft body tissues, maintains our temperature and hydric balance, gives sensory information to the brain and controls body moisture.
Skin is a physical barrier to the environment. It is the alteration of the barrier properties and actual damage to this barrier that causes dryness and dermatitis when the skin is exposed to soaps, water, chemicals, gloves and harsh weather conditions. The repair of the damage by moisturizers is related to the physical and chemical interactions of the ingredients with the natural skin barrier.
Finding an adequate sensitive skin care solution requires the understanding of some basic facts about your skin.
Skin Physiology: Composition and Function Basics
Skin has two main structural layersthe epidermis and the dermis.
- The epidermis is the outer layer of skin, which acts as the physical and chemical barrier to the interior body and exterior environment.
- The structural support of the skin depends on the deepest layer of the skin, called the dermis.
Epidermis and Stratum Corneum: The Composition and Growth of Skin
The epidermis consists of stacked layers of cells in transition. These cells are connected by protein bridges called desmosomes.
- The bottom layer of cells adjacent to the dermis are the basal cells which reproduce; they are in charge of skin cellular regeneration
- As the cells mature, they reach terminal differentiation while migrating upwards to the outer layer. Cellular physiology, shape, chemical composition and orientation change during the process of maturation.
- At the final stage, cells are called corneocytes, and they are already dead when they reach the stratum corneum, the top layer of the skin. Corneocytes don't have a nucleus and cellular structures.
- Corneocytes are flat, devitalized cells containing only water-retaining keratin proteins inside its membrane. The cellular shape and the orientation of the keratin proteins add strength to the stratum corneum. Stacked corneocytes represent about 10 to 30 layers of cells.
- There are more layers of stacked corneocytes in the thicker skin on the palms and soles.
- The cells remain connected to each other by protein bridges called desmosomes. The extracellular space is surrounded by stacked bilayers of lipids. The resulting structure is the natural physical and water-retaining barrier of the skin.
Filaggrin: The Breakdown of Skin
During the process of maturation, the viable cells moving towards the stratum corneum begin to clump proteins into granules.
- These granules are present in the granular cell layer of the skin and are filled with a protein called filaggrin.
- Inside granular cells, keratin proteins are combined with filaggrin. This way, proteolytic breakdown won't affect filaggrin.
- As the degenerating cells move towards the outer layer of the skin, enzymes break down the keratin-filaggrin complex; this process discard devitalized cells and rejuvenate the skin
- In the stratum corneum, water-retaining keratin remains inside the corneocytes, while filaggrin stays outside them.
When the moisture content of the skin is decreased, specific proteolytic enzymes in the stratum corneum are produced to further break down filaggrin into free amino acids. At this phase, a revitalizer serum will be useful to help skin recover itself.
A safer and biological option to chemical skin care treatments is now available in the form of a skin care product to treat a wide range of skin conditions.
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