Back to basics - What is the skin?

Gebhard Sophie

One of the questions that we never really asked ourselves but not the least: what constitutes my skin? 

Cosmetic products are, by definition, preparations intended to be brought into contact with the various superficial parts of the human body, in particular the epidermis which is the first layer of our skin. Their purpose is to clean, perfume, modify its appearance, protect, maintain it in good condition and / or correct body odor. 

What if understanding our products and routines involved knowing our skin? Let's zoom in a precise and a little microscopic way, on one of the heaviest organs of our body, that is to say 16% of the body weight!

First of all, our skin is made up of 3 superimposed layers all very different from each other: the epidermis, the dermis and the hypodermis .

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The epidermis: the first layer of the skin

It is the outermost layer of the skin that will come into direct contact with the outside. Its main function is to protect the organism from chemical, mechanical and microbiological agents.

On the surface of the epidermis we find two types of orifices: 

  • The pores: this is where the sweat flows. 

  • Ostias: these are orifices through which sebum flows and from which the hair or hair emerges. 

In addition, to avoid contamination with the inside of our body, this layer is devoid of blood vessels. There is all the same in the deep face of the epidermis an area which allows the epidermis-dermis cohesion. It is a wavy line called the dermo-epidermal junction which is involved in nutrient exchanges with the epidermis.

The epidermis is made up of keratinocytes which are the most important cells. They are superimposed in successive layers. Their function is to make a fibrous protein, keratin, which provides the skin with chemical and mechanical resistance

In this deep surface of the epidermis, we find melanocytes making melanin. This is the famous photo-protective pigment to protect the skin from the sun's rays . It is the one that is at the origin of the color of the skin, hair and eyes.

There are also Langerhans cells which are immune cells and merkel cells which have a role of sensory receptor .

The dermis: the second layer of the skin

It is located just under the epidermis, at the interface between the dermis and the hypodermis. It serves as a support and nutrition tissue for the epidermis but also for the cutaneous annexes: hair, body hair, nails, sebaceous glands which produce sebum and sweat glands that make sweat. 

The dermis is rich in blood and lymphatic vessels which allow nutrient exchanges with the deep layers of the epidermis. It is also a support tissue, a real framework of the skin, which gives the skin its extensibility and elasticity. It also helps to participate in the defense of the body thanks to white blood cells.

In addition, this layer will retain the 80% water of which the skin is made up. A real reservoir of water for the body. She will also synthesize collagen which allows resistance to stretching and elastin allowing the skin to stretch and then come back into place after deformation. 

The hypodermis: the third layer of the skin

It is the deepest layer of the skin. It is a support tissue that is both flexible and deformable, making it possible to form the interface between the skin and the organs it covers (muscles, bones). She is rich in fat cells. It is the body's reserve of fat and energy. 

The hypodermis also helps to absorb shocks and promote the sliding of the dermis on muscles and bones. It insulates the body and limits heat loss thanks to its distribution over the whole body. And finally, it shapes the silhouette of individuals according to their age, sex and nutritional habits. 

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