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You take care of it daily by applying various products in order to achieve healthy-looking skin. But do you know what your skin is made of and what are its functions?

As you may already know, the skin covers your entire body. This organ is composed of three main layers, the epidermis, dermis and hypodermis (Figure 1), which are responsible for the different functions of the skin (Marieb and Hoehn, 2010).

The epidermis, mainly composed of keratinocytes but also other types of cells, is on the outer surface of the skin and serves as a barrier by protecting the body from external aggressors such as UV rays, pathogens and various chemicals (Hirao, 2017)

The dermis is found beneath the epidermis and is primarily composed of extracellular matrix and fibroblasts (Marieb and Hoehn, 2010). These give the skin its resistance and elasticity properties. In the dermis, there are also skin appendages, each with their own functions: sweat glands, hair follicles and sebaceous glands.

The hypodermis, the deepest layer of the skin, helps connect the skin to the rest of the body (Marieb and Hoehn, 2010). This layer is primarily made up of adipose tissue that serves as an energy reserve, absorbs shock, and insulates against heat loss (Marieb and Hoehn, 2010).

Is the Skin an Organ?

The biggest organ in the body, to the surprise of many of us, is not the lungs or the stomach. The skin is the largest organ of the body! Weighing between 4kg and 10kg in adults, the skin covers more than 2 square meters of surface on our body.

The skin has many important functions, including protection from harmful microorganisms, controlling body temperature, regulating water balance and supporting vitamin D production!

• Protecting the body after trauma or injury;
• Ensuring a healthy body temperature;
• Maintaining proper fluid and electrolyte balance;
• Detection of painful and pleasant sensations;

Skin is considered essential to physical appearance. Skin color, texture, folds and lines influence appearance. Interference with skin functions such as perspiration, hair growth, skin repair and immunity can have health consequences.

What Are the Different Functions of the Skin?

Protection Against External Aggression

The skin acts as a protective barrier. The epidermis, especially the stratum corneum, is our body’s first line of defense, and works relentlessly to protect us from external aggressions such as UV rays from the sun, bacteria, and injuries.

The dermis is the second line of defense after the epidermis. The dermis contains a series of cells called lymphocytes and macrophages, which are able to recognize, alert the immune system and ultimately destroy invading bacteria, viruses and other pathogens. 

Energy Source

The area where fat is stored is a nutrient storage area, a key role of the hypodermis. When the body needs nutrients the stored fat is released in the areas where it is needed. This is a source of energy not only for the skin itself, but for the various internal organs. 

Interaction with Our Environment

The nerves that give the skin its sense of touch are found in the dermis. Touch and pressure are perceived by many nerve endings that allow the body to perceive things like pressure and different temperatures. Without touch, it is much more difficult to interact in our world!

Body Temperature Regulation

Parts of the skin such as hair follicles, sweat glands and blood vessels in the dermis allow our body to control its temperature. Evacuating our heat through our skin sets us apart from many animals! The layer of fat that makes up the hypodermis also plays an essential role as a thermal insulator against temperature variations.

Important for Survival

The skin, particularly the dermis, performs important functions for our well-being. This layer of the skin performs vital functions such as healing, regulation of body temperature, oxygenation and nutrient supply. It also has a protective function.

What Are the 3 Layers of the Skin? 

1. The epidermis, the Protective Layer

The epidermis is the outer layer of the skin, but it is much more than just an envelope. It is the thinnest of the three different types of layers that cover the body with a thickness of about one millimeter. Its cells are derived from the deepest part of the epidermis called the basal layer, where all new skin cells are created. These cells, the keratinocytes and melanocytes, move through the epidermis, molting until they reach the skin’s surface.

The outermost surface layer of the skin, called the “stratum corneum”, is made up of flat cells that are much thicker and can be found on the palms of the hands and soles of the feet. It is what we see when we look at the skin and is a protective layer against external aggressions! It renews itself very quickly: old skin cells are replaced every 28 days to keep a solid physical barrier. 

2. The Dermis

The dermis, the middle layer of the skin, is made up of collagen, elastin and other proteins like glycoprotein. Its support, flexibility and durability, gives the skin its shape. This layer allows nutrition to reach the epidermis. Its role is essential in the healing process, among others. It is home to hair follicles and sebaceous and sweat glands, as well as blood vessels and fibers. Its deterioration causes wrinkles and other signs of aging skin.

The dermis is divided into three layers: the papillary dermis, the reticular dermis and the deep dermis. The papillary dermis is a layer rich in nerve endings that is in constant interaction with the epidermis and the stratum corneum. The deep dermis is a connective tissue composed of elastic fibers.

What Is The Dermis Made Of?

Nerve endings for pain, touch, pressure and temperature

Nerve endings located in the dermis perceive things like pain and temperature in order to help us interact with our environment. The skin on the surface of the fingers and toes holds many nerve fibers and is therefore very sensitive to touch. 

The sweat glands to counteract heat and stress

When under stress, body heat builds up and causes sweat to be secreted. This process allows the body to get rid of water and salt, which allows the body to cool down. There are specific sweat glands for certain areas, such as the armpits and genital area.

The sebaceous glands for the secretion of sebum

Sebum is produced and secreted into the hair follicle in the sebaceous glands. Sebum is an oily liquid that helps moisturize the skin and prevents it from drying out.

Hair follicles for hair

Hair follicles produce hair all over the body. The hair that is generated in these follicles can also play a variety of roles, including regulating body temperature, resisting injury, and facilitating touch. These follicles also contain stem cells that can regenerate damaged epithelium.

Blood vessels in the skin supply the body with nutrients

Blood vessels dilate with temperature changes and as the body warms up, facilitating heat loss through the skin. 

3. The hypodermis, the Deepest Layer

The hypodermis is the layer of the skin where fat is stored. These layers of fatty tissue are located under the skin and are very useful, not only as an energy storage, but also to protect the surface of the skin from heat, cold and shocks.

Its main function is to store energy. The fat cells (adipocytes) of the hypodermis are held together by connective tissue, and it can form a thick layer: the amount of fat cells varies from a few millimeters (on the eyelids) to several centimeters (on other parts of the body).

What Is the Skin Made of?

The skin is made up of three distinct layers: the epidermis, the dermis and the hypodermis. From a chemical point of view, the skin is made up of different elements:

• 70% water;
• 27.5% protein;
• 2% fat;
• Salts, minerals and other trace elements;

Why Protect Your Skin from the Sun?

UVA or UVB (ultraviolet light) can cause skin burns, premature aging of the skin and increased eye damage. UVA or UVB radiation can also weaken your immune system, disrupt the function of your liver and increase the risk of skin cancer. The best preventative method is to use sunscreen to provide a barrier against the sun’s harmful rays.

What Happens when the Skin Is Damaged?

Soft, moisturized, well-protected skin has an even tone and good sensitivity to touch, pressure and temperature. But when the skin’s natural barrier is disrupted, its protective function and appearance are altered. The skin becomes dehydrated and loses its elasticity; it may appear rough, dry and chapped, or loose. The skin then becomes more fragile and vulnerable to the aggressions of external factors (sun and temperature variations). It is also more sensitive to infections.

When the body tries to repair damaged skin, it creates an immune response known as inflammation, which causes the skin to become red, raw and scaly. These are the skin’s own repair and regeneration mechanisms. In this state, the cells generate new epidermis, thanks to the continuous division of its stem cells.

Does Every Injury Leaves a Scar?

Our skin has several repair and regeneration mechanisms. The basal layer of the epidermis ensures the constant renewal of the epidermis by continuously creating new cells that are pushed to the skin’s surface. As long as the wound does not reach the basal layer, there will be no scarring.

• If the skin is scratched and the wound is only on the upper part of the skin, it will heal without scarring if it is cleaned and moisturized.
• If the skin damage reaches the basement membrane, the wound may result in scarring.

Why Do I Have Calluses On The Palms Of My Hands Or The Soles Of My Feet?

The epidermis is the top layer of the skin, protecting the soft tissues underneath from trauma that may be caused by sharp objects. It reacts to external conditions to better protect the dermis, hypodermis and internal organs, which sometimes has unpleasant results from an aesthetic standpoint.

After exposure to some external stimuli, the protective layer of skin that covers the outer layer of the body can thicken. An excellent example is the feet and hands: when subjected to repetitive rubbing, the stratum corneum can thicken and form calluses on the palms and soles of the feet.