Skin Structure

The skin - the largest organ of your body - is composed of three major layers:

• The epidermis
• The dermis
• The subcutaneous layer (also called the subcutis)

Epidermis

The epidermis is primarily composed of "keratinocytes," cells that renew themselves on a regular basis. The younger you are, the faster these cells turn over (approximately once a month in a young person). As you age, cell turnover slows, and skin becomes less elastic and flakier.

The epidermis is composed of many thin layers. The outermost layer, the stratum corneum, is visible to the human eye, and its dead cells shed regularly. (Scratch your arm and watch biology at work!)

The epidermis also contains melanocytes, which are responsible for melanin: the pigment found in your skin. The more melanin or pigment in your cells, the darker your skin color.

Dermis

The dermis (the Greek word for "skin") is also composed of several layers. It also is home to structures like blood vessels, hair follicles, sweat glands, collagen (protein fibers that support skin cells) and sebaceous glands.

Unlike the epidermis, the dermis is alive, with a vibrant blood flow fed by the blood vessels. When bacteria penetrate the dermis, an infection may develop.

The dermis' sebaceous glands-located everywhere on the body except for the palms of the hands and soles of the feet-produce sebum (oil), which is secreted through the sebaceous duct into the hair follicle. This is "ground zero" for acne, which develops when sebum travels from the sebaceous glands, to the hair follicles, up through the epidermis and into a pore that is visible on the skin surface. Oil, dead cells and bacteria join together and stick to a follicle, which forms a plug. This pollutes the pore and leads to an eruption.

While it may seem that a pimple pops up overnight, more often it takes weeks to develop. All of the activity is occurring beneath the surface of the skin, invisible to the naked eye-and you become aware of it only when you see that nasty little zit on your face.

Sebum production is generally highest in the "T zone": the forehead, nose and chin, which essentially form the letter "T" on your face. Sebum tends to build up in the pores of these areas.

Be advised, however, that sebum gets a bad rap because it is a critical component in keeping the skin healthy. It helps us clean our pores, shed dead cells and flush out bacteria. It gives hair and skin a healthy shine and keeps skin moist. It's when we produce too much sebum that pores become clogged and acne may develop. Adolescents, in particular, produce excess sebum and develop greasy skin and hair.

Subcutaneous Layer

The subcutaneous layer, or subcutis, lies beneath the dermis. It consists of adipose (fat) tissue, nerves and larger blood vessels.

Your Skin Has a Full-Time Job

The skin is a barrier against bacteria, water and other substances. It gives our body its shape and protects our internal organs. It also helps regulate body temperature and protects us from heat and cold.

Skin is elastic, constricting and contracting as needed. It also amazingly repairs itself when it is subjected to an insult, such as a cut, burn or acne lesion.

The Quest for Invisible Pores

The media have an obsession with perfect skin and invisible pores. If you don't have flawless skin, the message conveyed is that there is something wrong with you. Any fashion magazine cover can make the most secure woman feel like a beauty disaster. What many people fail to realize is that models are airbrushed and touched up on computer, and any imperfection vanishes. You probably wouldn't recognize the average supermodel walking down the street without the benefit of her makeup.

Human beings like the rest of us, however, have always been vain. Since ancient times, women applied dyes to their hair, skin and nails. Cleopatra can be considered the inventor of modern-day cosmetology.

While it is sometimes difficult to keep up with makeup trends and the hot colors that designers choose every new season, the pursuit of perfect skin never wavers.