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April 2017
Beauty and makeup
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THE SKIN’S FUNCTIONS



The skin carries out the following functions:

Protective function

The skin acts as a protective barrier against various types of mechanical stimuli, such as traumas, being pushed, rubbing or being hit, and it gets this property from the elasticity of its elastic and collagen fibres and the firmness of its tissues. In the areas of the skin that are most commonly exposed to mechanical stimuli, such as contact or rubbing, the stratum corneum is thicker (callus). Another example of this protective function is when the skin comes into contact with chemical agents, and this is thanks to the padding property of the skin: protection against solar rays is the job of melanin and a particular acid that is found in sweat, urocanic acid, and together they form a protective shield against UV rays.

Thermoregulating function

The skin works as both an insulator and thermoregulator, and this latter function depends on blood being taken to the cutaneous blood vessels and sweat glands. The alternation between vasoconstriction and vasodilatation in the capillaries causes very quick changes to the hematic flow and it is determined by the surrounding temperature. The sweat glands carry out a very important role in thermoregulation and, in fact, the body loses a large amount of heat through evaporation of sweat, and this happens when secretion is not visible (perspiratio insensibilis).
The adipose layer, which is thick in the hypodermis, has low thermal conductivity and therefore it plays a part in the skin’s thermoregulating function because it helps the skin to keep the body at a suitable temperature no matter what the surrounding temperature is (up to a certain point of course).

Sensory function

Thanks to the receptor organs, cutaneous innervation is able to perceive pressure, thermal and pain stimuli and transmit this to the nervous system which allows us to act accordingly to our surrounding environment. Sensitivity corpuscles and sensitive nerve endings are highly specialised therefore there are specific receptors for heat, cold, pain and itching. Pressure sensitivity varies depending on the different parts of the body, for example, the skin on the wrists and the back of feet are 3.5 times more sensitive than the abdomen or forehead. If a pressure stimulus on the skin becomes stronger, at first the tactile sensitivity feels like pressure and then, after, pain. If there are changes in temperature, receptors with specific conducting properties for heat and cold act quickly and make it possible for us to react to this new situation in a short space of time.

Respiratory function

Oxygen and carbon dioxide can be absorbed by the skin. Oxygen can reach the skin externally through the air and internally via blood, and some calculations show that the quantity of oxygen absorbed each day by the skin is approximately 5 litres.

Secretion function

Catabolites and waste products are removed from the body through the skin. It removes CO2, water and sebum as well as sodium ions, small quantities of potassium, magnesium, calcium and chlorine thanks to eccrine glands. When we do physical activity, this phenomenon can be balanced out by drinking, and this ensures we replenish our water and saline levels.

As well as being a softening agent for the skin, sebum also plays an antiseptic and anti-microbic role.

Anti-microbial defensive function

The skin’s bactericidal and fungicidal properties can be attributed to the acidity of the skin’s surface (which is approximately pH5) and the sebaceous glands’ hydrolipid film. Every time foreign substances penetrate the body, such as bacteria, viruses or fungi, an active protection process is started which is controlled by various types of cells, all of which are involved in immune protective functions.
The skin’s defensive abilities are very good when the skin is in a good condition, but if an individual suffers from acne of seborrhea, then these abilities are lowered because self-sterilisation is compromised and the composition of the sebum is different and it lacks some important elements.
Sebum and sweat travel outwards of the body and carry out an anti-microbic draining function, cleaning the sweat ducts and sebaceous follicles.

Reproductive function

The cell renewal process begins in the stratum basale, continues through the other layers and ends with keratinisation and flaking. The amount of skin we lose through this process is gradually replaced through continual cell renewal.

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