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.

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 hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (the hypodermis contains 50% of body fat). Fat serves as padding and insulation for the body.

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.

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.

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.

The most important way to care for your skin is to protect it from the damaging rays of the sun. Ultraviolet radiation damages the skin and can lead to wrinkles, premature aging, age spots, and cancer. Take extra precautions to make sure your skin is not exposed to the sun's rays. Use a natural sunscreen, or a moisturizer that contains sunscreen (at least SPF 15) everyday. Your skin does need some sunlight 10-15 minutes of direct exposure daily.

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.

Why is it that practically everyone in the middle class to the upper levels of demographics in any country are worried about getting wrinkles? Maybe it is the fear of getting old or looking old, or the wanting to look socially acceptable, or just plain vanity. We all have our own reasons. But whatever it is, everyone is united in wanting to solve this age old problem. However, in the first place, do we even have any idea about what actually causes these dreaded wrinkles? It's highly probable that we don't. The most important factor in finding a solution to any problem is finding out the root cause of it.

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".

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.

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 used on this page

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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