Eczema and psoriasis are both inflammatory conditions of the skin. The best way to understand these conditions and how to care for them is to learn as much as possible about them. As a start it is a good idea to go right back to the basics and learn about the skin itself.
The Human Skin
As in other mammals, human skin is composed of an outer layer, the epidermis, and an underlying layer of fibrous tissue called the dermis. Beneath the dermis is the subcutaneous fat.
There are two main kinds of human skin; Glaborous skin (non-hairy skin) and hair-bearing skin. Glaborous skin is found on the palms and soles and is characterised by a thick epidermis with dermatoglyphics (fingerprints).
Hairy skin differs from site to site, for example, the scalp versus the arm. It also contains a wide range of other structures depending on the part of the skin examined. Nails are formed from the epidermis on the fingers and toes. Oil glands (sebaceous glands) are found attached to hair follicles. Sweat glands are found in the dermis with ducts passing to the surface through the epidermis.
One of the most complex organs
In certain areas such as the axilla and groin there are specialised sweat glands called apocrine glands which develop after puberty. In addition there are specialised sense organs and nerves, blood vessels and other tissues such as muscle, which make the skin one of the most complex organs in the body.
The epidermis is constantly growing from the bottom upwards and the dead skin cells (stratum corneum) are shed (usually invisibly) from the surface. This whole process normally takes about 52-75 days but can be much quicker in some skin diseases such as psoriasis.
Some Quick Facts
- The average adult has 21 square feet of skin (2 sq m) which weighs 7lb (3.2 kg) and has approximately 300 million skin cells.
- On average each square half inch of skin contains: 10 hairs, 15 sebaceous glands, 100 sweat glands, 3.2 feet (1m) of tiny blood vessels.
- Skin is thickest on the palms & soles (1.2mm to 4.7mm) and thinnest on the lips and around the eyes. Facial skin is approximately 0.12mm thick and onthe body is about 0.6mm.