 Allergies [40]
Allergy is a disorder of the immune system often also referred to as atopy.
Antidepressants [27]
An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia.
Arthritis [18]
Arthritis is a group of conditions involving damage to the joints of the body.
Cancer [23]
Cancer is a class of diseases in which a group of cells display uncontrolled growth
Cardio & Blood [7]
Risk factors for heart disease: infections
Cholesterol [17]
A fat-like substance called a lipid. It is used to build cell membranes, hormones and bile acids
Diabetes [21]
The inability of the body to produce, or the inability to metabolize, the human hormone insulin; Diabetes insipidus, usually a disorder of the ...
Epilepsy [17]
Epilepsy is a common chronic neurological disorder characterized by recurrent unprovoked seizures
Gastrointestinal [13]
The digestive tract is the system of organs within multicellular animals that takes in food...
General Health [55]
The infant, child or young person’s current health condition
Herbal [16]
Herbal tea, herbal medicine
Hormonal [15]
Hormones - Proteins produced by organs of the body that trigger activity in other locations.
Men's Health [4]
For men on fitness, health, sex, caree
Pain relief [17]
Pain management is the medical discipline concerned with the relief of pain.
Skin care [17]
The skin is the outer covering of the body
Weight Loss [19]
Loss of body weight by dieting or due to various easting disorders or medical conditions.
Women's Health [12]
Find information on women's health issues, and lifestyle at the Women's Health
Fresh material Women’s health: more about endometriosis
→ More
The female reproductive organs: fallopian tubes and ovaries
→ More
Fertility: foresight's success
→ More
Menopause problems: causes and prevention
→ More
Women, work, and endometriosis
→ More
The most popular materials [5843 view]
preteen vagina → More
[3293 view]
Barium meal x-ray examination → More
[2385 view]
The female reproductive organs: fallopian tubes and ovaries → More
[2302 view]
Women’s health: more about endometriosis → More
[2258 view]
Women, work, and endometriosis → More
Awaiting moderation 17833 Article |
The principal functions of the skin THE PRINCIPAL FUNCTIONS OF THE SKIN
Firstly, it performs an essential protective role. Because of its resilience or ability to resume its previous shape after deformation, it can withstand considerable trauma without permanent damage. This mechanical barrier is mainly due to the arrangement and nature of the collagen and elastic fibres in the dermis. It also constitutes an effective barrier to the passage of substances into or out of the skin. This chemical barrier is provided by the layered cells of the epidermis, which impede the loss of water and body salts and prevent the penetration of external substances.
Secondly, the skin is a most effective and essential sensory organ. This is a result of it being richly supplied with nerve endings, which provide an effective sensory defence against potentially harmful stimuli. It also acts as a 'relay station' between external influences and internal organs, via a network of nerve fibres. Of equal importance, is its role as an organ of expression: for instance we may express anxiety by sweating, fear by pallor, anger by redness, pain as a grimace, or happiness with a smile.
Thirdly, the skin acts as a remarkable thermostat. This is mainly achieved by its blood vessels and sweat glands. The metabolic processes of the body continually produce heat, which must be dissipated to maintain a constant body temperature. Under normal environmental conditions this may be achieved by varying the diameter of the blood vessels in the skin, resulting in changes in the volume of the blood flow. This blood flow can be varied 100-fold from maximum constriction to maximum dilation of the vessels. Increased blood flow is accompanied by increased heat loss, whereas a reduced blood flow retains heat.
If, however, blood flow alterations are insufficient to regulate the body temperature, then the sweat glands are activated. This will occur with extreme external temperature increases, excessive exertion, or the fever accompanying an illness. The sweat bathes the skin and cooling results from its evaporation.
Fourthly, the skin plays an active part in the body's defence against such micro-organisms as bacteria, fungi, and viruses. The surface of the skin is never sterile. It is host to a permanent resident colony of various bacteria which are relatively innocuous. Their presence, however, inhibits the growth of more dangerous organisms on the skin. Further protection is provided by the dryness of the skin's surface. Most organisms are relatively intolerant to dry conditions, much preferring humid or moist environments. The continual shedding of the superficial epidermis also discourages bacterial invaders. Sebum, the oily secretion produced by the active sebaceous glands, contains fatty adds which have a strong anti-bacterial and anti-fungal action. A thin coating of this on the skin provides a further protection.
Finally, the skin is an important barrier against damaging ionizing radiation, such as ultra-violet light. For skin unprotected by hair or clothing, the only significant defence against the destructive effects of U.V.L. is melanin. Without melanin the epidermis would be a thin transparent membrane, allowing
U.V.L to damage the sensitive structure of the dermis. Melanin is a complicated large protein produced by special cells, melanocytes in the basal layer. From there it is distributed throughout the epidermis. The amount of melanin in the epidermis governs the colour of a person's skin: the more melanin, the darker the skin colour. There is no difference though in the number of melanocytes in white and in black skin. The difference is simply one of activity, reflected in the amount of melanin or pigment these cells produce. Various factors may influence this, including sun exposure, pregnancy, various hormonal disorders, and drugs.
*5\44\4*
«Buy Generic Viagra»
 Версия для печати
Количество просмотров: 432
| Keywords for this page: The principal functions of the skin |
|
|
