In zootomy and dermatology, skin is an organ of the integumentary system composed of a layer of tissues that protect underlying muscles and organs. As the interface with the surroundings, it plays the most important role in protecting against pathogens. Its other main functions are insulation and temperature regulation, sensation and vitamin D and B synthesis.

Skin has pigmentation, provided by melanocytes, which absorbs some of the potentially dangerous radiation in sunlight. It also contains DNA repair enzymes which reverse UV damage, and people who lack the genes for these enzymes suffer high rates of skin cancer. One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner. This has sometimes led to the classification of people on the basis of skin color. See the article on human skin color.

Skin is composed of the epidermis and the dermis. Below these layers lies the hypodermis(subcutaneous adipose layer), which is not usually classified as a layer of skin.

The outermost epidermis is consists of stratified squamous epithelium with an underlying basement membrane. It contains no blood vessels, and is nourished by diffusion from the dermis. The main type of cells which make up the epidermis are keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum, granulosum, spinosum, basale. Cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate, inducing expression of new types of keratin genes. They eventually reach the corneum and become sloughed off (desquamation). This process is called keratinization and takes place within about 30 days. This layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out.

The constantly peeling off dead cells of the epidermis mix with the secretions of the sweat and sebaceous glands and the dust found on the skin to form a filthy layer on its surface. If not washed away the dirt and dead skin slurry begins to decompose emitting a foul smell.

Functions of the skin are disturbed when it is dirty and it becomes more easily damaged. The release of antibacterial compounds decreases. Dirty skin is more prone to develop infections. Cosmetics should be used carefully because these may cause allergic reactions. Each season requires suitable clothing in order to facilitate the evaporation of the sweat. Sunlight, water and air play an important role in keeping the skin healthy.

In fact, skin care and protection should be an essential part of your health, fitness, and beauty regime. If you take care of your skin, your skin will take care of you! If your stuck in a skin care rut, or if you are just looking to learn a bit more about the basics of skin care, read on to learn more about this important step in your daily activities.

You are never too young or too old to start taking care of your skin. In fact, skin care and protection should be an essential part of your health, fitness, and beauty regime.

Exercise, rest, and good nutrition lay the foundation for beautiful, healthy skin, inside and out. A proper diet is not only good for your overall health, it also helps to ensure that your skin will receive all of the vitamins, minerals, and nutrients that it needs to maintain and repair cells. Drinking purified water is another good way to keep your skin healthy. Water helps to hydrate the skin and move waste and nutrients through the system. It is very effective mixing a teaspoon or capful of Organic Apple Cider Vinegar in with your water. Do not drink Tap Water.

When you do use soap, try using a natural very mild soap that does not contain any dyes, parabens or perfumes. Follow up the bath with a moisturizing lotion, concentrating on problem dry areas. A good all natural moisturizer is one of the foundations for a healthy skin care regimen. Continue moisturizing throughout the day to keep skin healthy. Your hands and face are particularly susceptible to daily damage, and may need to be moisturized several times.

A skin care routine does not have to be elaborate in order to be effective. But you should develop some kind of skin care routine based on your skin type, daily activities, and nutritional needs so that you can be sure you are taking the very best care of your skin. Following a daily skin care regime will also allow you to more closely evaluate your skin for abnormalities.

Wash your skin thoroughly on a daily basis to remove the dirt, debris, pollutants, and perspiration that accumulates on a daily basis. If you have dry or sensitive skin, use only warm water to wash your skin and use a mild natural cleanser every few days. If you have normal or oily skin, be sure to wash with a gentle cleanser on a daily basis. Be sure to brush your teeth before washing your face, as toothpaste residue can irritate sensitive facial skin.

Acne, pimples, sunspots, age spots, wrinkles and other blemishes are skin conditions that plague people the world over. The global beauty industry already makes billions of dollars every year as women everywhere embark on quests to preserve (or achieve) a youthful, glowing appearance. Responding to this need, dermatologists, and other specialists continue to look for the best and safest possible treatments and formulations to combat skin ailments, the most common of which is acne.

As we age, our body undergoes various changes, and so does our skin. In our skin, we have tissues known as collagen and elastin. These tissues are mainly responsible for making our skin firm and stretchable. As we grow older, the amount of collagen and elastin in our skin naturally diminishes. As a result, our skin becomes less elastic and weaker, thus creating "wrinkles".

Experts say that the amount of wrinkles that a person will develop through the years also depends on the genetic make up of this individual. However, smoking, sun exposure, dry skin, and repetitive facial expressions and mannerisms such as frowning, can all enhance the creation of wrinkles that may or may not be permanently present.

For people seeking solutions to severe damage that has already been done to the skin, there are a number of treatments available ranging from chemical peels and dermabrasion to the latest and technologically advanced, computerized laser resurfacing. However, many people looking for skin repair are hesitant to try chemical or laser peels due to the painful procedure and long recuperation period they have to undergo. The results of these procedures however, are fantastic.

One less painful procedure is the particle skin resurfacing procedure. The process is removes the outer layer of skin in a highly controlled manner. Because of its preciseness, it is practically painless. By repeating this procedure a number of times, the younger skin moves to the surface, thus promoting visible changes in the skin's texture, color and appearance. The benefits of this skin resurfacing procedure are that it causes very little pain or discomfort, no recuperative period is needed, there is minimal risk, it can be used for all skin types, and no anesthesia is required.

The important thing to remember when seeking out treatment for your wrinkles is to know first how your body can possibly react to the treatment. Get in touch with a skin doctor for things that you are not sure of, but are contemplating on trying out.

Definitions and terms

Acne

• An inflammatory disease of the sebaceous glands and hair follicles of the skin that is marked by the eruption of pimples or pustules, especially on the face.

Bacteria

• Microscopic unicellular prokaryotic organisms characterized by the lack of a membrane-bound nucleus and membrane-bound organelles.

Dermis

• The sensitive connective tissue layer of the skin located below the epidermis, containing nerve endings, sweat and sebaceous glands, and blood and lymph vessels.

Epidermis

• The outer, protective, nonvascular layer of the skin of vertebrates, covering the dermis.

Hypodermis

• A subcutaneous layer of loose connective tissue containing a varying number of fat cells.

Pimples

• A small swelling of the skin, usually caused by acne; a papule or pustule.

Ultraviolet radiation

• Invisible electromagnetic radiation between visible violet light and X rays.

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