Skin is vital to our global health and wellness. In addition to acting as the body's first line of defense against bacteria and viruses, healthy skin maintains fluid balance and helps regulate body temperature. It is very sensitive and recognizes the softest touch as well as pain. It is the largest and most visible organ, covering almost 2m² and representing almost 1/6 of our body weight. The state of the skin can also have a significant impact on our self-esteem.
Skin structure
The skin, a constantly changing dynamic organ, is made up of three main layers: epidermis, dermis, and subcutis, or subcutaneous tissue, each of which is made up of several sub layers. Skin annexes, such as sweat and sebaceous glands and follicles, also play various roles in its overall function.
Epidermis
The epidermis, as the outermost layer that we see and touch, protects us against toxins, bacteria and fluid loss. It consists of 5
sub layers of skin cells called keratinocytes. Produced in the innermost basal layer, these cells migrate to the surface of the skin, maturing and undergoing a series of changes. This process, known as keratinization (or cornification), makes each of the sub-layers different.
Basal layer (or basal layer) : It is the innermost layer, where keratinocytes are produced.
Thorny layer (or prickly layer) : Keratinocytes produce keratin (protein fibers) and become spindle-shaped.
Granular layer (granular layer) : Keratinization begins: cells produce hard granules and, as they push upwards, they change to keratin and epidermal lipids.
Clear layer (lucid layer) : The cells are densely compressed, flattened and cannot be distinguished from each other.
Horny layer (or stratum corner) : It is the outermost layer of the epidermis and comprises, on average, about 20 sub-layers of dead cells, flattened, depending on the part of the body that covers the skin. These dead cells are regularly shed in a process known as flaking. The horny layer is also the seat of the pores of the sweat glands and the openings of the sebaceous glands.
The cells of the horny layer are united to each other by means of the epidermal lipids. These lipids are essential for skin health: they create your protective barrier and fix moisture. When lipids are missing, the skin may become dry and may feel tight and rough.
The epidermis is covered by a water and lipid (fat) emulsion known as a hydrophilic film . This film, maintained by secretions from the sweat and sebaceous glands, helps keep the skin supple and acts as an additional barrier against bacteria and fungi.
The aqueous part of this film, known as the protective acid mantle, contains :
Lactic acid and various amino acids from sweat.
Sebum free fatty acids.
Amino acids, pyrrolidinecarboxylic acid and other natural moisturizing factors (FHN), which are predominantly by-products of the keratinization process.
