Skin Structure: Dehydrated Skin

The skin is the largest organ of the human body. It has a protective role against physical aggressions such as friction, infections, chemicals and UV rays.

Structure & organization

It is a set of cells organized in several layers and covering the entire body. The skin is made up of three distinct compartments: the epidermis, the dermis and the hypodermis.

The epidermis

It is the outer layer of the skin, it combines impermeability and resistance. Its thickness varies from 75 to 150 µm and it is renewed in about 1 month depending on the person. The epidermis is made up of 4 different regions:

• The basal layer : in contact with the dermis, it is composed of a layer of cells: keratinocytes . These multiply rapidly in order to renew skin cells. There are also melanocytes , which produce melanin, a pigment that protects the skin from the sun's rays. The more melanin grains there are in the keratinocytes, the darker the skin. This layer also houses Langerhans cells , which are part of the body's defense system.

• The spinous layer : superposition of 4 to 5 thicknesses of keratinocytes linked together, this promotes the impermeability of the skin. Gradually, from the base to the surface, the cells accumulate melanin and are loaded with keratin.

• The granular layer : cells filled with keratin move closer to the surface of the skin and begin to break down.

• The stratum corneum : the most superficial layer of the skin. Dead cells form a layer that is eliminated by desquamation.

The dermis

Thick and located under the epidermis, it represents the skin's support tissue. Its thickness varies depending on the area and can reach up to 1 cm at the back. Composed of 80% water, it is very rich in elastin and collagen fibers. It is therefore both strong, flexible and elastic. Its main functions are nutrition, thermoregulation and healing.

It also contains hair , sweat glands (which produce sweat) , sebaceous glands (which produce sebum) and blood vessels (which provide nutrients).

To maintain the suppleness and resistance of the skin, cells in the dermis, fibroblasts , produce collagen (which gives the skin its suppleness) and elastin (which allows the skin to be elastic).

Cells of the immune system ( lymphocytes and macrophages ) are present in the vessels of the dermis and constitute the second line of defense after the epidermis.

The hypodermis

Flexible and deformable, its role is to serve as an interface between the skin and the muscles it covers. Very rich in fat cells ( adipocytes ), it is particularly thick in parts of the body subjected to significant pressure, such as the buttocks. This fat can be mobilized in the form of energy in the event of exercise or fasting. It also participates in thermal regulation, by acting as an insulator.

Dehydrated skin

When the skin is dehydrated, it becomes uncomfortable and tight. This is because the epidermis no longer plays its role as a waterproof membrane as well and the water contained in the skin evaporates more than it should.

The natural phenomenon of evaporation, also called Transepidermal Water Loss (TEWL), naturally present, is more significant on weakened skin than on normal skin.

Indeed, the stratum corneum is covered with a hydrolipidic film (water, sweat and sebum) which forms a protective barrier against bacteria (thanks to its acidic pH). An alteration of this barrier can make the stratum corneum permeable and allow water to escape, thus leading to an increase in TEWL and dehydration of the skin tissue.

Several factors can weaken this barrier. There may be external factors such as cold, pollution, tobacco, stress; and internal factors such as skin aging, certain diseases or menopause.

To protect and care for this precious barrier, you can first avoid external factors as much as possible, then on a daily basis favor gentle cleansers, and moisturize your skin with a day cream and a night cream.