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Human skin is a remarkable organ, the body's largest, but it is often taken for granted. Most people are content to let skin be until dryness, oiliness, a rash or a wrinkle rouses attention. But once they understand how skin functions, many reconsider the importance of the skin and the quality and content of the skin care products they use. Using natural skin care can make more of a difference than most folks realize.
Consider these facts:
1 . An adult's skin comprises between 15 and 20 percent of the total body weight.
2. Each square centimeter has 6 million cells, 5,000 sensory points, 100 sweat glands and 15 sebaceous glands.
Skin is constantly being regenerated. A cell is born in the lower layer of the skin called the dermis, which is supplied with blood vessels and nerve ending. The cell migrates upward for about two weeks until it reaches the bottom portion of the epidermis, which is the outermost skin layer. The epidermis doesn't have blood vessels but does have nerve endings. The cell spends another two weeks in the epidermis, gradually flattening out and continuing to move toward the surface. Then it dies and is shed.
Two billion to 3 billion skin cells are shed daily. The body expends this effort to replace skin every month because the skin constitutes the first line of defense against dehydration, infection, injuries and temperature extremes. Skin cells can detoxify harmful substances with many of the same enzymatic processes the liver uses. The unbroken surface also prevents infectious organisms from penetrating into systemic circulation. As gatekeeper, the skin absorbs and uses nutrients applied topically. Because it cannot completely discriminate, the skin may absorb the synthetic chemicals often present in soaps and lotions and other skin care products, which at best it has no use for and at worst can be toxic or irritating.
Most of our site visitors are committed to natural foods and remedies, but many aren't as selective when it comes to personal skin care products. These otherwise savvy shoppers might purchase any sale shampoo, skin care cleanser or lotion. But because new skin is constantly being generated and because it plays such an important protective role, it makes sense to choose nourishing natural skin care products.
The Epidermis
The epidermis is the topmost layer of the skin. It is the first barrier between you and the outside world. The epidermis consists of three types of cells keratinocytes, melanocytes and langerhans cells. Keratinocytes, the cells that make the protein keratin, are the predominant type of cells in the epidermis. The total thickness of the epidermis is usually about 0.5 - 1 mm. At the lowermost portion of the epidermis are immature, rapidly dividing keratinocytes. As they mature, keratinocytes lose water, flatten out and move upward. Eventually, at the end of their life cycle, they reach the uppermost layer of the epidermis called stratum corneum. Stratum corneum consists mainly of dead keratinocytes, hardened proteins (keratins) and lipids, forming a protective crust. Dead cells from stratum corneum continuously slough off and are replaced by new ones coming from below. The skin completely renews itself every 3 - 5 weeks. Most mild peels work by partly removing the stratum corneum and thus speeding up skin renewal.
Another significant group of cell in the epidermis are melanocytes, the cells producing melanin, the pigment responsible for skin tone and color. Finally, Langerhans cells are essentially the front door of the immune system in the epidermis. They prevent unwanted foreign substances from penetrating the skin.
The condition of epidermis determines how "fresh" your skin looks and also how well your skin absorbs and holds moisture. Wrinkles, however, are formed in lower layers.
The epidermis consists of many layers:
The stratum corneum, or outer layer: This layer is made of flattened epithelial cells in multiple layers. These layers are called keratinized layers because of the buildup of the protein keratin in those cells. Keratin is a strong protein that is specific to the skin, hair and nails. This layer of skin is, for the most part, dead. It is composed of cells that are almost pure protein.
The translucent or transitional layer: This is a translucent, thin layer of cells. This layer is sometimes visible in thick skin; however, nuclei and other organelles are not visible. The cytoplasm (the amorphous area between the nucleus and the outer membrane of the cell) is mostly made of keratin filaments.
The suprabasal layers. This is three to five layers of flattened polygonal cells that have granules in the cytoplasm. Below them is a layer of cube-shaped cells that also contain bundles of keratin filaments.
The basal or cell-division layer: This layer is just above the basement membrane and the dermis. It is a single layer of cells that undergo cell division to renew the upper layers of the epidermis.
Since the human epidermis is renewed every 15-60 days, proper surface nutrition feeds the cells of the basal layer. Exfoliation will remove dry or damaged skin of the outer layer to allow newer cells to be visible.
The Dermis
The dermis is the middle layer of the skin located between the epidermis and subcutaneous tissue. It is the thickest of the skin layers and comprises a tight, sturdy mesh of collagen and elastin fibers. Both collagen and elastin are critically important skin proteins: collagen is responsible for the structural support and elastin for the resilience of the skin. The key type of cells in the dermis is fibroblasts, which synthesize collagen, elastin and other structural molecules. The proper function of fibroblasts is highly important for overall skin health.
The dermis also contains capillaries (tiny blood vessels) and lymph nodes (depots of immune cells). The former are important for oxygenating and nourishing the skin, and the latter -- for protecting it from invading microorganisms.
Finally, the dermis contains sebaceous glands, sweat glands, hair follicles as well as a relatively small number of nerve and muscle cells. Sebaceous glands, located around hair follicles, are of particular importance for skin health as they produce sebum, an oily protective substance that lubricates and waterproofs the skin and hair. When sebaceous gland produce too little sebum, as is common in older people, the skin becomes excessively dry and more prone to wrinkling. Conversely, overproduction or improper composition of sebum, as is common in adolescents, often leads to acne.
The dermis is the layer responsible for the skin's structural integrity, elasticity and resilience. Wrinkles arise and develop in the dermis. Therefore, an anti-wrinkle treatment has a chance to succeed only if it can reach as deep as the dermis. Typical collagen and elastin creams, for example, never reach the dermis because collagen and elastin molecules are too large to penetrate the epidermis. Hence, contrary to what some manufacturers of such creams might imply, these creams have little effect on skin wrinkles.
Subcutaneous tissue
Subcutaneous tissue is the innermost layer of the skin located under the dermis and consisting mainly of fat. The predominant type of cells in the subcutaneous tissue is fat cells. Subcutaneous fat acts as a shock absorber and heat insulator, protecting underlying tissues from cold and mechanical trauma. Interestingly, most mammals lack subcutaneous tissue because their fur serves as a shock absorber and heat insulator. Sweat glands and minute muscles attached to hair follicles originate in subcutaneous tissue.
The loss of subcutaneous tissue, often occurs with age, leads to facial sag and accentuates wrinkles. A common procedure performed by dermatologists to counteract this process is to inject fat (collected elsewhere in the body) under the wrinkles on the face.
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These statements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease. |
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