11

FUNCTIONS OF THE SKIN AND ITS DISEASES

The skin provides protection from damage and entry of bacteria, regulates temperaturę; it is also an excretory and sensory organ.

Physical protection from damage is provided mainly by the epidermis. Thickness of the subcuta-neous tissue also plays an important role in protecting against some injury. The skin acts as a barrier against the entry of microorganisms, protects the body against Chemicals in the environment and ultravioletrays in the sunlight.

The skin acts like a waterproof coat for the body, preventing rapid absoiption or evaporation of water and electrolytes at the surface of the body. In this way it helps to keep the ąuantity of water in the body constant. However, smali amounts of water continuously evaporate from the skin surface. Through this process which is calledperspiration the body loses 500 ml of water a day.

Regulation of temperaturę is a very important function of the skin. The skin contains a great number of sweat glands, which excrete sweat. The sweat consists of 95% (per cent) of water, 2% of dissolved salts, a smali ąuantity of urea and about 3% of carbon dioxide. In hot temperaturę or great "muscular activity the sweat flows as fluid on the surface of the skin, which is cooled by its evapora-tion. By means of perspiration the body eliminates excessive amount of fluid and some salfs, which mainfamnhiheral balance of the body.

The skin is a delicate sensory organ providing information about the environment. Millions of nerve endings located in the skin are sensitive to various stimuli: touch, pain, pressure, heat, cold and itching. Another special function of the skin is secretion of ear wax by the extemal ear and sebum or oil by sebaceous glands.

The skin is exposed to morę injuries than any other organ of the body. It is affected by many types of infections: bacterial, viral, fungal, as well as infections with parasites, such as scabies. Skin cancer, i the mostcommon of which is skin melanoma, usually begins as a dark mole. It is freąuently triggered by excessive exposure to the sun rays. Skin allergy and irritation by harmful Chemicals cause many kinds of dermatitis (or eczema) which are the commonest of all occupational diseases. Acne, which is common in adolescence, is a condition of overactivity of sebaceous glands! Psoriasis is a chronic skin disorder that causes an overproduction of epithelial cells. Skin lesions are classifiecfas primary or secondary. Primary lesions, which do not cause a break in the skin, comprise: acne, rash, eczema, furuncle, erythema and dermatomycosis. Secondary lesions, which break the skininclude: crusts and fissures causedby dermatitis, excoriations and ulcers.

EXERCISE A. Answer the following ąuestions.

1.    What are the main functions of the skin?

2.    Which layers of the skin play an important role in protecting from injury?

3.    What is sweat excreted by?

4.    How is the body temperaturę regulated?

5.    What stimuli are nerve endings sensitive to?

6.    What are other special functions of the skin?

EXERCISE B. Define the following terms.

Sweat..........................................................

Perspiration................................................

Waterproof.................................................

Acne...........................................................

Psoriasis.....................................................

Skin melanoma..........................................

Primary lesions..........................................

Secondary lesions......................................

E. Doncsch-Jeżo - English for Medical Students and Doctors — 1

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