Karen Priemer, BSN RN ARBONNE INTERNATIONAL Regional Vice President
		Independent Consultant # 10037686

Anatomy of the Skin Sebum, Sweat, Skin pH and Acid Mantle Sebum is an oily secretion produced by sebacious glands, tiny ducts adjacent to hair follicles. Sebum is secreted into the follicle, from which it spreads over the hair and skin. The main role of sebum is to waterproof the skin and hair. Both excess and lack of sebum are undesirable. Excess sebum is associated with oily skin and acne. It is particularly common in adolescents as the increased levels of sex hormones stimulate sebum production. Lack of sebum, which is common in middle and older age, leads to skin dryness and accelerates wrinkle formation. Sweat is a salty, watery solution produced by sweat glands, numerous microscopic channels opening onto the skin surface. As sebum and sweat mix up on the skin surface, they form a protective layer often referred to as the acid mantle . Acid mantle has a particular level of acidity characterized by pH from about 4 to 5.5. A pH of 7 is considered neutral, above 7 is alkaline, and below is acidic. The pH of acid in the human stomach, for example, is usually from 1 to 2, which is highly acidic. The skin, on the other hand, is mildly acidic. In addition to helping protect skin from "the elements" (such as wind or pollutants), acid mantle also initits the growth of harmful bacteria and fungi. If acid mantle is disrupted or loses its acidity, the skin becomes more prone to damage and infection. The loss of acid manlte is one of the side-effects of washing the skin with soaps or detergents of moderate or high strength. What Is the Skin Made of? The skin is the largest organ in the body, comprising about 15% of the body weight. The total skin surface of an adult ranges from 12 to 20 square feet. In terms of chemical composition, the skin is about 70% water, 25% protein and 2% lipids. The remainder includes trace minerals, nucleic acids, glycosoaminoglycans, proteoglycans and numerous other chemicals. The skin consists of three main layers: epidermis, dermis and subcaneous tissue. 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 protien keratin, are the predominant type of cells in the epidermis. The total thinkness 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 cylce, 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 a forepost of the immune system in the epidermis. They prevent unwanted foreingn substances from penetrating the skin. The condition of epdermis determines how "fresh" your skin looks and also how well your skin absorbs and holds moisture. Wrinkles, however, are formed in lower layers. 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 elastrin 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 sebacious glands, sweat glands, hair follicles as well as a relatively small number of nerve and muscle sells. Sebacious 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 sebacious 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 treatement 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 Subcutanous 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 adipocytes or 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 occuring 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. Important Skin Molecules Health, resilience and youthful appearance of the skin depends, among other things, on several key classes of biological molecules, just like the quality of a house depends on the quality of bricks, beams and concrete. The most important skin molecules are collagen, elastin, glycosoaminoglycans and proteoglycans. Collagen is a protein forming the structural grid that holds other skin structures. It plays a role somewhat similar to that of steel rods in a reinforced concrete block. It gives the skin its strength and durability. As any other protein, collagen is composed of amino acids. However, it is unusually rich in a few specific amino acids, proline, hydroxyproline, lysine and glycine. Some experts believe that foods or supplements rich in these amino acids may benefit the skin by stimulating collagen production. There is a number of other ways to stimulate collagen production, including topical vitamin C and copper peptides. Increasing collagen production is important because age-related decline in the collagen synthesis is partly responsible for the signs of skin aging such as thinning,  wrinkles and sagging. Elastin is also a protein. It is more stretchable than collagen and helps maintain skin resilience and elasticity. Elastin contains two special amino acids, desmosine and isodesmonsine. When both elastin and collagen and abundant and undamaged, the skin easily regains its shape after being stretched or folded. Just as collagen, elastin deteriorates with age, leading to wrinkles and facial sag. Glycosoaminoglycans (GAGs) and proteoglycans are special biological polymers whose key role is to hold moisture in the skin. In essense, they are extremely effective natural moisturizers - far more                effective that common cosmetic moisturizers. Hydrated GAGs and proteoglycans help the skin stay plump and fresh and provide mechanical support for skin cells. GAGs are composed of special units (mainly water-holding sugars) such as glucosamine hydrochloride, N-acetyl glucosamine, and glucosamine sulfate. These units combine to form various types of GAGs, such as hyaluronic acid, keratin sulfate, heparin, heparin sulfate, dermatin sulfate, and chondroitin sulfate. Proteoglycans are larger than GAGs and are formed when certain types of GAGs are attached to a protein backbone. Since GAGs and proteoglycans are composed largely of water-holding sugars, supplementing one's diet with these sugars may enhance the skins production of GAGs and proteoglycans. In particular, N-acetyl-D-glucosamine, D-glucosamine hydrochloride, and D-glucosamine sulfate are often used as supplemets to increase skin moisture.