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 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.

Skin can be dividided into thick and thin types. Thick skin is present on the soles of the feet and the palms of the hands. It has a larger stratum corneum with a higher keratin content. Thick skin does not grow hair; its purpose is to help grip. Thin skin is present on the bulk of the body and has a smaller stratum corneum and fewer papillae ridges. It has hair and is softer and more elastic. The characteristics of the skin, including sensory nerve density and the type of hair, vary with location on 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.

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.

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.

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 first step to taking care of your skin is preventing damage. Sun, wind, pollutants, and simply aging can degrade the condition of your skin. Common complaints include dry and itchy skin, wrinkles, sagging, color changes, and age spots. There are steps that you can take to keep you skin looking and feeling its best.

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.

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.

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.

Definitions

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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