The skin is made up of several layers placed one on top of the other:
- The epidermis: the outermost layer of the skin, the epidermis is covered by the stratum corneum, similar to a pile of flat, resistant cells. It serves as a protective envelope, sheltering the body from microbes. It is studded with pores from which sweat escapes to cool the skin. It is also home to tiny receptors linked to the brain, including pain receptors. Finally, an oily, aqueous and invisible film, called the hydrolipidic film, ensures the skin remains impermeable and moisturised. The epidermis also acts as sun screen and produces melanin, the pigment which gives the skin its colour.
- The dermis: Highly vascularised, the dermis is a tissue rich in elastin and collagen fibres, which confer it its elasticity and strength. At the heart of its fibres and cells, this tissue is home to sebaceous glands, sweat glands and hair follicles. It also contains a multitude of nerve endings and blood vessels, and sensors which react to pressure or to touch. With age, the dermis slackens and creases, which is how wrinkles form.
- The hypodermis: Serves as an interface between the dermis and the mobile structures located below it, such as the muscles and the tendons. It also protects the body from physical shocks, temperature variations and serves as an adipose tissue store.
The skin therefore functions like an actual ecosystem. It requires special care as it is essential to the body.
DID YOU KNOW? The skin, a living organ
The skin of an adult human being represents a surface area of around 2 square metres! Its weight is around 3.5 kilos in women and varies between 4.5 and 5 kilos in men, making it the largest organ in the body. It undergoes specific cycles and is able to tell the difference between day and night, and even reacts to certain components and fragrances (according to its pH) – the skin is permanently changing. In order to be able to play its role of a protective screen, it sheds 2 layers of dead cells daily. This explains why the epidermis is renewed more than 1,000 times over 70 years of life!