Skin science 101

Did you know that the skin is the largest organ in the human body? It accounts for 15% of your body weight. It is versatile, fulfilling several functions that are vital to your health and well-being.

Main functions of the skin

Like a physical barrier, the skin protects the body in several ways. It insulates and protects the internal organs from shock and physical damage. Moreover, the skin’s external surface is relatively resistant, helping defend against infections and preventing external substances from penetrating. It also retains water, electrolytes and proteins within the body. Lastly, it is equipped with a mechanism commonly referred to as tanning, which, to a certain extent, protects the body from the sun’s rays.

Five skin appendages help the skin fulfill its protective function:

  • hair
  • sebaceous glands (oil)
  • nails
  • eccrine and apocrine sweat glands

The metabolism is the set of chemical reactions in the skin that allow it to regenerate, repair itself and respond to stimuli in its environment. Through the various chemical reactions that occur within the skin, substances are produced to help maintain tissues and organs. For example, when exposed to UV rays, the skin synthesizes vitamin D using several compounds in the body. In addition, the skin regulates body temperature by either releasing excess heat or preserving heat. Temperature is reduced through sweating. Sweat glands are abundant at the skin’s surface. Heat loss also occurs though the dilation of capillaries in the skin. When the capillaries near the surface of the skin dilate, they transfer heat to the cooler surrounding air through a process known as convection.

The sweat glands produce sweat, releasing water and minerals in order to help maintain a balance in the inner environment. In addition, these glands eliminate waste and toxins, such as the degradation products of certain medications.

As a result of its many nerve endings, the skin is sensitive to pressure, vibration, touch, pain and temperature.

The skin is able to repair wounds.

The skin selectively absorbs fat-soluble vitamins A, E and K, and steroid hormones, since the human body is unable to synthesize them. The skin’s capacity to absorb certain substances makes it possible to apply lotions, creams, gels and transdermal patches topically in order to provide therapeutic or medicinal treatment.

The skin plays an important psychological role. It reveals emotions (e.g., shy people tend to blush easily). The skin is also the most visible health indicator (e.g., acne, dermatosis as a result of stress). This living organ that envelops the whole body enables communication between individuals. It affects the perception that you have of yourself, as well as your perception of others. When skin is healthy and problem free, it fulfills its functions optimally, allowing you to feel comfortable and confident.

Structure of the skin

The skin is composed of three layers:



The thin outer protective layer.



The elastic and resistant intermediate layer.



The layer of adipose and connective tissue beneath the dermis.



Much thinner than a sheet of paper, the epidermis provides a waterproof barrier against the intrusion of viruses, bacteria and other foreign substances. Cells called KERATINOCYTES make up 90% of the epidermis. The two other key cells in the epidermis are LANGERHANS cells (immune cells) and MELANOCYTES (pigment cells). The function of the epidermis is to form a healthy corneal layer. The epidermis is itself made up of five layers:

  • 1. Stratum corneum or horny layer: this outermost layer is composed of keratinocytes, dead, flattened cells that contain a protein called keratin. It keeps the skin hydrated and protects the human body from environmental stresses such as chemicals, UV rays and microorganisms. The corneal layer regenerates itself approximately every 28 days.
  • 2. Stratum basale or basal layer: keratinocyte stem cells are born in this layer. Melanocytes are found in this layer. The basal layer anchors the epidermis to the dermis.
  • 3. Stratum spinosum or spiny layer: a layer of spiny cells.
  • 4. Stratum granulosum or granular layer: a layer of granular cells.
  • 5. Stratum lucidum or clear layer: this layer occurs only in the palms of the hands and on the soles of the feet.



The primary function of the dermis, located beneath the epidermis, is to nourish and provide structure for the epidermis. It also plays an important role in the regulation of body temperature. Its structural matrix is composed of connective tissue, mainly fibrous proteins, namely collagen, elastin and a sugar called glycosaminoglycans, which is responsible for producing hyaluronic acid. Collagen, elastin and other fibrous proteins are produced by cells called fibroblasts, present only in the dermis. These proteins give skin a resistance to traction. When skin ages, fibroblasts tend to decrease along with the elements of the extracellular matrix (collagen, elastin and glycosaminoglycans). The skin thins, becoming less elastic, and wrinkles appear.

The dermis therefore provides structural support for the epidermis. The dermal structures and cells provide the epidermis with nutrition, sensory perception and an immune response, since it lacks blood vessels, nerve tissue and some, but not all, immune cells.

Fibroblasts also play a role in wound healing: when an injury occurs, they multiply and produce, in addition to collagen and elastin, growth factors that form scar tissue.


Hypodermis or subcutaneous tissue

Located beneath the dermis and composed of fat (or adipose) cells called ADIPOCYTES, the hypodermis is highly vascularized. It plays a vital role in the storage and release of fats, thereby managing the body’s energy reserves. It atrophies with age, contributing to the visible thinning of the skin.

The skin is therefore a living organ that is constantly growing and regenerating. It is important to ensure its daily care and provide it with the right nutrients according to its needs – for example, in order to speed up the elimination of dead cells at its surface, lighten and even the complexion, and increase the production of collagen, elastin, hyaluronic acid and other elements needed to ensure its proper functioning.

Whether for preventive, regenerative or corrective purposes, a proper skincare routine is necessary at any age. To ensure that you use the right products for your skin type and your concerns, it is important to consult a professional. Use our locator to find a clinic.

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