skin structure anatomy

Structure of human skin

We all want to take the best possible care of our skin and keep it healthy and glowing. This is possible, but only if we know its structure and what it needs.
The skin is the largest sensory organ in the human body and consists of two main layers - epidermis and dermis (Fig. 1).
Fig.1 . Main anatomical parts of the skin.

Epidermis

The epidermis is the outermost layer of the skin and acts as a protective barrier against the environment. The production of vitamin D also takes place in it.
 
It itself is made of 5 layers (Fig. 2).
epidermis structure
Fig.2. Structure of the epidermis.
1. The stratum corneum or horny layer is the outermost layer of the epidermis, which takes care of preserving moisture in the skin and on which we apply cosmetic products . Its structure is likened to the "bricks and mortar" model (fig. 2.1.) and consists only of dead skin cells called corneocytes (the bricks), which are embedded in a complex of lipid layers (the mortar). Lipid layers, in turn, are made up of ceramides, cholesterol and fatty acids and aim to reduce water loss through the skin.
stratum cormenum structure
Fig. 2.1. Schematic representation of the structure of the stratum corneum .

Corneocytes in the stratum corneum contain a mixture of hygroscopic substances. They are called NMF (natural moisturizing factor) or natural moisturizing factor. NMF plays the role of a humectant and consists mainly of: amino acids, lactic acid, urea, sugars and minerals. The components of NMF are water-soluble and can easily be washed off the skin when it is dry and does not have a sufficient lipid layer to serve as protection.

2. Stratum lucidum is also a layer of dead cells and is only present on the parts of the body with thicker/rougher skin such as the hands and heels.

3. The granular layer (stratum granulosum) consists of horizontally arranged keratinocytes (skin cells), in which the appearance of granules is observed (Fig. 2.), because they have begun to lose their vitality.

4. The spinous layer (stratum spinosum) is responsible for the synthesis of lipids and proteins.

5. The basal layer (stratum basale) is the place where new keratinocytes are formed.

In addition to keratinocytes , the epidermis also contains other cells, including melanocytes, which are responsible for the synthesis of the melanin pigment. Melanin is the pigment that gives skin and hair its color.

Briefly, the functions of the epidermis :

  • Retaining moisture in the skin
  • Maintaining optimal lipid content
  • Providing immune protection
  • Antioxidant function
  • Vitamin D synthesis
  • Skin colour
  • Replacement of the stratum corneum

What happens with dry skin?

With healthy skin, potential irritants and allergens cannot pass through the stratum corneum. However, this is not the case when the skin is dehydrated . With dehydration , the skin cells (bricks) shrink and "cracks" appear, which allow the passage of various irritants and cause redness, itching, peeling of the skin, etc. Therefore, it is very important that our skin is hydrated both from the outside and from the inside.

Derma

Just below the epidermis is the second main layer of the skin - the dermis . Its function is to support the upper layer and procure the necessary substances and oxygen by means of capillaries, since there are no blood vessels in the epidermis . The dermis also contains the sebaceous glands , which are located all over the body except for the palms, heels and feet. They are most concentrated on the face and scalp, and for this reason, these are also the main places where the "favorite" of all acne appears. Their function is to produce sebum to act as a lubricant for the skin and reduce water loss.

What is transepidermal water loss (TEWL)?

Besides being a barrier, another major function of the skin is to retain water in the body. The phenomenon of transepidermal water loss is actually the continuous movement of water from the lower to the upper layers of the skin, where at some point it evaporates (a process different from sweating) and when our skin is compromised (dry, irritated, red), this loss of water increases. That is why it is important to use a cream that creates a protective film on the skin, retains moisture in it and keeps it healthy.

We hope we have been at least a little helpful. With this, we are far from exhausting the topic of skin structure and we are yet to introduce you to more and more interesting and useful facts.

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