Skin Appendages

The skin is flexible and elastic to permit tension-free movements, especially at the joints. Its secretions make it particularly resistant. Pigments contained in the germ layer determine the color of the skin. The skin adapts to the mechanical strain on the different areas of the body. The dermal ridges (a special marking on the surface of the skin) develop individually as a hereditary pattern in each person so that impressions of the pads of the fingers and toes as well as the balls of the feet and hands enable a person to be identified (dactyloscopy, ie, finger print analysis).

The skin appendages are the hair and nails as well as the glands in the skin, namely sweat, sebaceous, olfactory, and mammary glands.

Hair and nails are formed by the epidermis and take on protective and tactile functions. Hairs are long keratin filaments that grow from the hair bulb out of the subcutaneous tissue through the epidermis. The hair bulb is supplied with tactile nerves, muscle fibers, and sebaceous glands.The hairs can be involved in the sense of touch because of the nerve supply; as a result of the muscle supply, the hairs may become erect (goose-flesh) and thus be used for heat regulation.

Nails are horny extensions of the epidermis and correspond to the claws or hooves of animals. They provide protection for the finger pads but also act as an opposing surface to enhance the sense of touch in the fingertips. The sense of touch is reduced when a nail is lost. The nails are formed as horny plates in the matrix of the nail bed. Destruction of the nail bed leads to growth abnormalities or loss of the nail.

Skin glands (dermal glands) comprise the sebaceous glands as well as small sweat glands and olfactory glands. The olfactory glands are particularly large sweat glands, which include the ceruminous glands (which secrete ear wax). The skin contains around 20 million small, knotlike sweat glands. The dermal glands are singlecell or multicellular acinous (berrylike) or tubular glands in the skin that secrete their products directly outward (exocrine glands). These mucous, sweat, and sebaceous glands form a protective film for the skin. The mammary glands are transformed sweat glands. The ceruminous and lacrimal glands are special kinds of dermal glands.

Skin atrophy (wasting or thinning of the skin) develops as a normal sign of aging because of the breakdown of the skin's constituents, their individual layers, and elastic fibers, which causes a decrease in skin tone. The skin becomes pale, gray, dry, thin, and wrinkled; the blood vessels in the skin stand out more distinctly because of thinning of the overlying layers.

Skin bacteria are the bacteria living on healthy skin as a main constituent of the skin flora, which are found on more moist areas of skin such as the scalp, the face, the palms of the hands, the armpits, between the toes, and in the glandular ducts and hair follicles.They cannot be completely removed by washing or strong disinfectants and they repeatedly spread out quickly from the channels in the skin.The most important skin bacteria are aerobic and anaerobic bacteria such as staphylococci, corynebacteria, sarcinae, streptococci, mycobacteria, as well as fungi.

Working in the laboratory with dental technology materials (active and auxiliary materials) can result in skin hazards that particularly affect the hands, forearms, neck, and facial areas. This can cause irritation and dryness of the skin or sensitization (development of an allergy) originating from plastic monomers, dust from metal grinding (chromium, nickel), and acrylic mixing fluids (eg, for artificial stone).

Frequent hand-washing and working with wet hands as well as metal, plaster, and acrylic dust are particularly stressful to the skin. People who suffer from hay fever, neurodermatitis, or generally dry skin are especially at risk. Regularly using skin protection and skin care products and avoiding contact with occupational materials that irritate the skin are important protective measures. Chemical or mechanical irritation of the skin through constant exposure will break down the skin barrier. When working with such occupational materials, dental technologists should take the following precautions:

• Protect the skin with skin care products including moisturizing cream
• Avoid contact with irritants
• Wear protective gloves, clothing, and glasses/ mask
• Use suction cleaning tools