Diseases And Disorders Of The Skin And Face

Diseases And Disorders Of The Skin And Face...
The skin is the largest organ of the body, making up about 15 per cent of the total body weight. It comprises an outer cellular epidermis firmly attached to a fibrous dermis containing blood vessels, lymphatics, nerves and free cells (Fig. 31/1). It protects the body mechanically, keeps water and bacteria out, prevents the undesirable loss of tissue fluid. 

It assists the maintenance of a steady body temperature and is a most important sense organ. Emotions are expressed via the skin, sometimes involuntarily, as in the flushing of rage and shame, the pallor of anger and emotional sweating in anxiety. The skin is liable to a large variety of disorders, most of which do not harm the general health but cause distress because they are unsightly or because they itch.

Several false notions regarding skin diseases are prevalent, particularly that they are contagious, that they are caused by 'nerves' or by defective diet and that very little can be done about them. In reality only a few skin diseases are significantly contagious, the commoner ones being virus warts, scabies, pediculosis, bacterial impetigo and syphilis. Genuine examples of skin disorders caused directly by emotion or diet are un¬common and are usually fairly easily recognized. Many skin problems are completely curable with treatment, some resolve spontaneously, and the remainder can often be greatly alleviated by judicious therapy.

Terminology of skin lesions. Since skin diseases may have widely differing appearances in different sites it is necessary to learn the definitions of the various types of skin lesions.

Macule, a flat spot of a different colour from the surrounding skin. Freckles are macules.
Papule, a small lump raised above the surface of the skin. Nodule, a more deeply situated lump.
Scale, a flat mass of horny cells shed from the horny layer.

Crust, a dried deposit on the skin. Usually refers to dried serum, but occasionally the term is applied to thick keratin.

Blister, a skin bleb filled with clear fluid.

Vesicle, a small blister.

Pustule, a skin bleb filled with pus.

Excoriation, a scratch mark.

Plaque, a raised uniform thickening of a portion of the skin with a flat or rough surface and a well-defined edge.

cyst, a deeply situated fluid-filled cavity.

Erythema, redness of the skin resulting from dilatation of dermal blood vessels.

Erosion, an area of superficial loss of skin.

Ulcer, an area of loss of the full thickness of the skin or mucous membrane.

The extent of lesions is indicated by terms such as sparse, scattered, extensive, profuse, and confluent. If the whole skin surface is inflamed the patient is said to have an erythrodermia. A skin disease is a dermatosis (plural, dermatoses).