Canadian Psoriasis Foundation
Fondation canadienne du psoriasis

Understanding Your Skin

Your Body's Largest Organ

• protecting you from bacteria and other infectious agents,
• shielding you from the environment
• preventing you from dehydrating (drying out), and
• keeping you in touch with the rest of the world.

Your skin will always respond positively to being cared for!.

Each 28-day cycle is a new opportunity to help your skin become healthier. Give it the care it needs. It's never too late to start. You must cleanse it, moisturize it, and nourish it every day.

You can make your skin healthier. Whether you are male or female, young or old, you can begin with learning how your skin works.

Looking from the outside in

On the top layer or epidermis, a layer of dead cells at the outer surface acts as your body's primary shield. The skin cells of the epidermis began life deeper inside the epidermis. They started out as basal cells (from the base of the epidermis). They move up to your skin surface, pushed from beneath by more rapidly-dividing basal cells. As they near the surface, they fill with keratin. Keratin is a fibrous protein and its name comes from the Greek word, keras, meaning horn. Keratin accumulates inside the epidermal basal cell until it nearly replaces the living cell machinery. The skin cells now form a tough, hardened shield.

When the epidermal cells reach the skin surface, 28 days after the start of their journey as basal cells, they have withered, died, and bound themselves firmly to one another. The tough, nearly impermeable part of the epidermis, called the stratum corneum, has now been formed. This keratin shield is bathed in a very thin but effective layer of salty sweat and acidic, oily sebum called the acid mantle. Many foreign organisms perish on contact with your skin. The stratum corneum and acid mantle are your body's first line of defence.

Your skin is always shedding. Shedding prevents many microbes from penetrating the skin. Suppose a bacterium latches on to a skin cell. As the epidermis renews the keratin shield, it sheds the dried up cells on the surface -- at the rate of about one million every forty minutes. The old cells curl up and peel off, flying into space with the microorganisms perched on them. When your body sheds skin cells, you are literally throwing out the trash.

Sebaceous glands located in the epidermis pump out the sebum that lubricates your skin and hair. Body oils, combined with sweat forms the acid mantle that covers the keratin layer. Soap removes the acid mantle from your skin. It takes about 90 minutes for your body to replace it.

To limit the damaging effects of the sun on the body, natural pigment-producing cells called melanocytes inject surface cells with the pigment melanin. There are 60,000 melanocytes in each square inch of skin. Skin colour differences depend on the amount and distribution of melanin produced by the melanocytes. Vitamin D is produced by the skin when it is exposed to sunlight.

Underneath your epidermis is a thick mass of connective tissue called the dermis. The dermis and the deeper fat cells act as shock absorbers, padding the body's inner tissues from outside blows. Blood vessels help regulate body temperature, widening or constricting to release or conserve heat. The dermis is also the structure that gives skin its overall texture, flexibility, and resiliency. On cold days the arrector pili muscles contract, causing the hair to stand up. In people, this condition is known as "goose bumps."

Throughout the dermis snakes a warning system of nerve fibres that terminate in nerve endings. These can be free nerve endings or nerve endings that are enclosed in corpuscles. This network tingles in response to touch, pressure, heat and cold, alerting the brain to the body's contact with the world outside itself.

Looking at skin with psoriasis

At the patches with psoriasis, the skin cells move from the base of the epidermis to the surface in about 5 days, instead of the normal 28 days. In psoriasis, the epidermis is thicker (the cells haven't had time to flatten and dry out) which is why the psoriasis patch stands out as a raised area compared to the unaffected skin. Fluid and blood are more prevalent in these patches because the skin cells are still young and plump.

In psoriasis patches, the stratum corneum does not have the same pliability and toughness as in normal skin. This is likely because it did not have enough time to develop the keratin found in unaffected skin. Consequently, it cracks and flakes easily. Psoriasis can be very painful in areas where skin needs toughness and pliability such as the palms of the hands, soles of the feet, genitals, knees, and elbows.

Strangely enough, harmful bacteria and organisms still find it difficult to penetrate psoriatic skin, even though its effectiveness as a barrier has been reduced by psoriasis.

The dermis is also different when someone has psoriasis. The blood vessels are wider than normal. The patches are red and bleed more easily than the unaffected skin. There are also an unusually high number of white blood cells in the dermis, which will occur whenever skin is inflamed. In pustular psoriasis, the epidermis may not thicken as much as in common psoriasis but there is more inflammation. Collections of white blood cells form small abscesses which create the small pus spots that people with this type of psoriasis have.

The Last Word

You are a partner in your own health care. Take the responsibility of finding the simple small things that can help you feel better. There are skin care tips others have found will help. We hope that they will help you, too.

Copyright © 1999. The Canadian Psoriasis Foundation.
Updated September 1,1999