Overview to better understand the corneal layer, which makes it far more services than we think.
To explain and popularize what is the stratum corneum, Gérard Redziniak, scientific advisor and innovation in the fields of cosmetics and dermopharmacie, likes to explain that “itis created in the course of the climb of small cells. “They are at the start, in a kind of maternity cell that is the basement membrane, where there are small keratinocytes, surrogate mothers who are going to make little babies cells : the keratinocytes, which will differentiate into the different layers of the skin“. Subsequently, these small cells, which are born at the base of theepidermis, will swell in the swelling of keratin and covering of cement lipid.
Although the stratum corneum was seen for a very long time as the first layer of our skin, the one with which the outside is directly in contact, we now know that it is covered with bacteria, which can go up to a million per square cm : this stratum microbiotome, as the baptize Gérard Redziniak, acts synergistically with the first layer of the skin. In fact, the bacteria are useful to strengthen it and give it a better quality.
In the first place, it serves to keep the water inside the body. Gérard Redziniak reminds us that “the body is an aquarium, composed of 70% water by weight, which must represent 95 % of water molecules. To ensure that this water remains to the interior, with its 60 000 billion cells, the stratum corneum, acts as the edge of the aquarium“.
The horny layer is also a barrier against UV filters, with keratins and proteins of which it is composed. They will be reflective and see their penetration in the dermis slows down. So far, the stratum corneum can not entirely stop these rays. Sun exposure should therefore be limited, in order not to disrupt the cellular life and not to alter its nature, and, in response to this aggression, it may thicken, wrinkle and dry out.
Finally, in function of its water content, it will determine the type of skin of each one. To consider that the epidermis is properly hydrated, it is necessary that it has between 12 to 14 % water.
It is possible to measure the volume of water content in the stratum corneum, a process called cornéométrie. “By a technique of impedance by passing a small electric current on the surface, and if the current passes, it means that the skin is properly hydrated, “adds Gérard Redziniak.
“The hygiene is to be monitored, but it must be careful not to over wash either. The goal is not to disturb the hydrolipidic film, this cosmetics natural surface that allows the balance with the stratum microbial and the stratum corneum,” advises Gérard Redziniak. “In addition, it is better to wash in the evening, because it is during the day we accumulate a lot of pollutants that directly affect the stratum corneum“.
Finally, Gérard Redziniak reminded that everything depends on the nature of the skin of each one, he insists on the fact “that in the function of the genome, the stratum will be different.” From one person to another, it is necessary to adapt the answers cosmetics to protect the skin better. The stratum is the first layer produced by the skin to combat the aggressions, but it can be destabilized if it is too attacked. Where the notion of prevention when you are young, and prevention-repair when they start to age and that the first signs of aging appear, skin dryness, micro-wrinkles).
The stratum corneum is changing over time. Its quality also depends on those of keratinocytes, which originate on the basement membrane, at the junction of the epidermis and the dermis. This “maternity cell“, says Gérard Redziniak, will regenerate less quickly during aging. The cells on the surface, (called corneocytes) form the stratum corneum, takes about 28 days to re-form when we are young. From the age of 50 and beyond, the epidermis is going to put close to two months before you renew. In appearance, the skin becomes thinner, due to a slowdown of the reconstruction cell.
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