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.

Mammalian skin often contains hairs, which in sufficient density is called fur. The hair mainly serves to augment the insulation the skin provides, but can also serve as a secondary sexual characteristic or as camouflage. On some animals the skin is very hard and thick, and can be processed to create leather. Reptiles and fish have hard protective scales on their skin for protection, and birds have hard feathers, all made of tough β-keratins. Amphibian skin is not a strong barrier to passage of chemicals. A frog sitting in an anesthetic solution will quickly go to sleep.

The skin is often known as "the largest organ in the human body". This applies to exterior surface, as it covers the body, appearing to have the largest surface area of all the organs. Moreover, it applies to weight, as it weighs more than any single internal organ, accounting for about 15 percent of body weight. For the average adult human, the skin has a surface area of between 1.5-2.0 square metres, most of it is between 2-3 mm thick. The average square inch of skin holds 650 sweat glands, 20 blood vessels, 1000 melanocytes, and more than a thousand nerve endings.

The skin on a person's face is seen by people that person interacts with. For some people, therefore, facial skin care is of particular importance, and they often use cosmetics to deal with the appearance of the face and condition of the skin, such as those for pore control and black head cleansing.

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.

Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in ears, the nose and fingertips.

The main cell types of skin are fibroblasts, adipocytes (fat storage) and macrophages. Sebaceous glands are exocrine glands which produce sebum, a mixture of lipids and waxy substances: lubrication, water-proofing, softening and antibactericidal actions are among the many functions of sebum. Sweat glands open up via a duct onto the skin by a pore.

The skin supports its own ecosystems of microorganisms, including yeasts and bacteria, which cannot be removed by any amount of cleaning. In general these organisms keep one another in check and are part of a healthy skin. When the balance is disturbed, e.g., by antibiotics which kill bacteria, there may be an overgrowth and infection by yeasts. The skin is continuous with the inner epithelial lining of the body at the orifices, each of which supports its own complement of flora.

If you take care of your skin, your skin will take care of you! But with all of the lotions, creams, and potions on the market, it can be difficult to know which product will work for you. Many products claim to remove wrinkles or heal dry skin. Others claim to contain expensive ingredients that they say will improve the effects of the product.

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.

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.

Use a natural sunscreen when possible, regardless of whether or not you plan on spending much time in the sun. The sun's rays are very damaging and if you get in the habit of applying sunscreen everyday, you will never be left without protection. The suns most beneficial rays occur at sunrise and sunset.

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.

Apart from the services offered at skin clinics, many creams, gels and ointments that claim to treat acne, diminish sun or age spots and enhance skin elasticity are widely available in the market. There are scrubs, cleansers, masks, over-the-counter skin medicine and skin peel formulations, all offered at various price ranges. Most can be bought at department stores or drugstores, but the fact is that very few of these so- called miracle products actually work.

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.

Over the years, beauty experts and skin doctors have come up with a vast array products to treat and minimize wrinkles. Anti-wrinkle creams and ointments help reduce the appearance of wrinkles and prevent new ones from forming. These wrinkle ointments and anti-aging creams help a lot in restoring the skin's firmness and elasticity. In addition, these products contain anti-oxidants and retinol that not only aids in reducing wrinkles and fine lines on the skin, but also stimulates collagen production.

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.

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.

While it is true that physical beauty is just skin deep, it is still no reason why people, particularly women, should disregard basic skin care. Since the skin is our outermost layer, it is exposed to the harsh elements of the environment. And because it is not uncommon for people to base judgments from our cover, with the face being the first thing they look at, it is only proper that we go to great lengths to keep our skin looking clean and fresh.

Terms explaining

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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