Facts and figures about the skin
- At around two square metres, the skin is a human’s largest organ. It makes up around 15 percent of a person’s body weight.
- At two to four millimetres, the skin is at its thickest on the hands and feet. It is at its thinnest, at 0.03 millimetres, on the eyelids.
- The skin renews itself every 28 days. Every day we lose up to 15 gram of skin cells. It is skin cells that account for half our house dust.
- Our body’s casing contains two to four million sweat glands, with a particularly high number on the soles of our feet – up to 700 per square centimetre.
- These sweat glands produce up to 10 litres of sweat per day as a result of hard work or extreme heat.
A multi-talented organ with many different functions
Our body’s casing is fitted with sensory cells, i.e. receptors, making it highly sensitive. These allow it to detect touch, pain, warmth and cold. A particularly high number of receptors are located on the fingertips, lips and erogenous zones.
The skin plays a major role in the external appearance and physical attractiveness of a person.
The skin protects the body from losing water from the inside and ensures that no water penetrates the body tissue from the outside.
Thanks to its own air conditioning system, the skin is able to protect the body from overheating (through sweating) and hypothermia (through increased blood circulation of the internal organs).
Three layers, three functional areas
Each skin layer has its own special function: the epidermis, which can be seen and felt, is a protective shield both inside and out. Its functions include fending off chemicals and all kinds of pathogens.
The dermis is composed of connective tissue fibres. These ensure that the skin is both stable and elastic, while the fat layer of the subcutis serves to cushion bones and tendons and protect them from hypothermia.
How hard skin develops
The uppermost epidermal layer contains dead horny cells (keratin), which are normally shed. However, when a body part is exposed to undue pressure, rubbing or improper load distribution, e.g. from poorly fitting shoes, the skin builds up a thick protective layer – and hard skin or calluses are formed. This layer is particularly thick in places subject to heavy strain, such as the heels or soles of the feet. To get rid of hard skin, it is advisable to proceed gently: soften the skin in a foot bath, carefully remove the hard skin with a pumice stone, then apply cream thoroughly.
Language used in reference to the skin
«How important the skin is for us is revealed by our language», dermatologist Yael Adler writes in her book «Haut nah» (skin close). There are days when we don’t feel comfortable in our own skin, or so tense we jump out of our skin at every little thing. A «thick skin» is required at work, and those without are deemed thin-skinned. Disinterested people claim: «It’s no skin off my nose», while things get under the skin of those more sensitive. And people who flee from adversity are out to save their skin. The famous conductor Nikolaus Harnoncourt once said that after a concert he felt «skinned».
White as a sheet or bright red
The current emotional state of a person is evident from their skin and especially from the colour of their face. The fact that we turn white as a sheet in moments of shock and horror is a vestige from primeval times: in a fight or flight situation, more blood was automatically pumped to the required muscles and organs and less to those body parts of little importance, like the skin. The result: we turn pale as a ghost. By contrast, there are times when we turn red, which can also be the result of unpleasant feelings – such as shame, nervousness or anger. In these cases, nerve impulses cause the skin vessels to dilate, resulting in either bright red skin or red stress patches on the face or neck.
A pleasant frisson and...
A gentle breeze or a soft caress: getting goose bumps can be a wonderful sensation. The fact that dermatologists calls this a «hair erection» is no accident, explains Yael Adler. Controlled by the vegetative nervous system, the hairs which in fact lie at an angle in the skin straighten up, «and the layers of skin surrounding them bulge upwards in a hump.» This is possible because at the depth of each hair follicle lies a small traction muscle.
...the shock of the cold
Getting goose bumps and raised hairs in the cold was a phenomenon also known to prehistoric man. The fluffing up of the «fur» helped prevent heat loss. The same mechanism was used to scare off enemies as bristled (neck) hair makes a person appear taller and broader. Why emotional moments (watching love films or listening to favourite music) cause us to shiver has not yet been conclusively clarified, says Yael Adler, but is another example of how closely the skin and nervous system are connected.
Why we have which skin colour
From white and pink to yellow and orange or brown and black, the human skin comes in a wide range of colours. This diversity is genetically and geographically determined: depending on the «top coating», it is easier to adapt to different living conditions. The substances responsible for this are melanins, i.e. pigments in the epidermis.
How these two forms are mixed determines the colour of a person's skin, eyes and hair. And each has advantages and disadvantages, depending on the person’s habitat. In Nordic countries, phaeomelanin makes the very light skin of the inhabitants more permeable to the sparse UV rays, which is important for forming vitamin D. Under an intensive southern sun, however, light skin types must be careful. These people burn quickly; darker skin types are better protected.
Good bacteria, bad bacteria
Up till now, research on the optimal combination of micro-organisms that protect the body from diseases and support the immune system has mostly been conducted on the gut’s microbiome. However, increasing focus is now being placed on what inhabits our skin. Here too, the microbiome protects us from harmful intruders and wards them off. However, if an imbalance develops in the colonisation, the skin can become inflamed and subject to disease. It's therefore important to create good conditions by ensuring an intact lipid barrier and acid mantle. Dermatologist Severin Läuchli, says: «Don't overdo it with washing. Choose a product that, depending on your skin type, is not too oily and preferably free of fragrances, dyes or preservatives.»