Skin condition, Cell, Human skin

 Skin condition, Cell, Human skin

Human skin


What is the skin for

The structure of the skin

The skin and the main problems

How to take care of the skin

Normally also called skin, the skin is the largest organ in the human body and constitutes its outer covering. It is a dynamic organ, which changes continuously, and together with the so-called skin appendages, that is the hair, nails, and glands that are inside it, constitutes the integumentary system.

Skin surface

In adult men, the skin surface extends on average for about 1.5-2 square meters and its thickness can vary according to sex and age, but also according to the area of the body. The skin, in fact, is usually thicker in correspondence with the muscles and joints of the arms and legs, on the back, on the soles of the feet, and on the palms of the hands.

The color of the skin varies from person to person and according to ethnicity and depends mainly on the amount of melanin contained in the skin. Melanin is a pigment produced by melanocytes, cells found in the basal layer of the epidermis, ie the outermost layer; its function is to protect the skin from the harmful action of the sun's ultraviolet rays.

One of the most important characteristics of the skin is its elasticity, which allows it to stretch to adapt to the progressive growth of the organism. Furthermore, the skin is able to regenerate itself to repair damage or wound.

What is the skin for

Covering the whole body, the skin represents, first of all, a fundamental protective barrier for the organism against "dangers" that can come from the outside: 

  • trauma or injury
  • dangerous chemicals
  • harmful microorganisms 
  • such as viruses and bacteria, ultraviolet rays.

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In addition to protecting from external factors, the skin plays a fundamental role in maintaining the balance of fluids and electrolytes within the body, protecting it from the damage of dehydration.

Its functions, however, do not end here. The skin, in fact, is very important in the body's thermoregulation process, in which it participates both through the action of the sweat glands and through the regulation of blood flow:

  • according to the temperature
  • in fact, the blood vessels of the skin increase or reduce their diameter
  • thus controlling the dispersion of heat.
  • In addition, the nutrients and energy that the human body may need accumulate in the hypodermis: if necessary, they are released into the blood and transported to the tissues.

Other functions of the skin are:

  • the production of substances important for metabolism, such as vitamin D
  • the perception of sensations
  • the definition of the somatic features and the aesthetic aspect of each person.
  • The structure of the skin
  • From the anatomical point of view, the skin is made up of three main overlapping layers :
  • subcutaneous layer (also called subcutaneous or hypodermis)
  • dermis epidermis.

The subcutaneous layer is the innermost one and is made up of adipose cells, ie fat cells that have the task of insulating the body from heat and cold and to accumulate and conserve energy. 

Fat cells are held together by a spongy connective tissue. 

In different areas of the body, the subcutaneous adipose tissue can be more or less thick and the amount of cells in the various areas is different in men and women.

The dermis is the intermediate layer, consisting of an elastic and fibrous connective tissue formed mainly of collagen and elastin, proteins that give the skin particular characteristics of resistance and elasticity. 

This layer is rich in blood vessels, which transport and distribute the nutrients it needs to the skin, remove waste, and contribute to the body's thermoregulation.

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In the dermis, there are also numerous nerve endings, which allow us to perceive sensations such as pain, pressure, temperature, etc. 

The areas of the body where the dermis is very rich in nerve fibers are particularly susceptible to certain stimuli, as in the case of the fingertips, which are sensitive to touch.

This layer is also rich in sebaceous and sweat glands. 

The former secrete sebum, an oily substance that acts as a protective barrier to the skin and makes it soft and shiny. 

The sweat glands, on the other hand, produce sweat as a response to certain stimuli, such as stress and high temperature.

Finally, the dermis contains the hair follicles, from which the different types of hair of the human body are generated, which help to protect the skin from possible injuries and to thermoregulate the body. 

The amount of hair follicles in the dermis differs in different areas of the body: 

  • the scalp, for example, is extremely rich in them, unlike the palms or soles of the feet.
  • The dermis, therefore, with all its structures, has the task of nourishing the skin and protecting the body from dangerous external agents; 
  • In addition, it contains fibroblasts, connective tissue cells that help repair skin lesions.

Five layers

The epidermis is the outer layer of the skin, and is in turn formed by five layers, which from the outside to the inside are:

  • the stratum corneum
  • the shiny layer
  • the granular layer
  • the spinous layer
  • the basal layer.


This structure makes the epidermis, even if relatively thin, particularly resistant to mechanical damage, and allows the selective passage of different substances from the outside to the inside and vice versa.

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The epidermis is mostly made up of keratinocytes, cells specialized in the production of keratin, which is also the main component of nails, hair and hair.

The dead cells of the epidermis are transported to the superficial layers and eliminated: this process is called desquamation.

In addition, the epidermis contains a particular type of cells that are part of the immune system (Langerhans cells), which help detect foreign agents and protect against infection.

Stratum corneum

The stratum corneum, which is the most superficial layer of the epidermis, is formed by corneocytes, flat cells with no nucleus, and lipids. Its structure can be thought of as a wall, in which the corneocytes represent the bricks and the lipids the cement that surrounds them.

The stratum corneum represents an important protective barrier for the skin: if it is intact, it prevents foreign substances and potentially harmful microorganisms from entering the body.

The hydrolipidic film, a thin film that covers the epidermis, is essential for maintaining the correct physiology of the skin: it is composed of a mixture of water, salts, and proteins produced by the sweat glands and a mixture of lipids released by the sebaceous glands. The hydrolipidic film is able to retain the water produced by the glands, maintaining the correct hydration of the skin.

The skin and the main problems

The general well-being of the organism is also closely linked to the health of the skin.

Healthy skin forms an effective protective barrier and performs its functions optimally.

However, when the skin is damaged, it can lose some of its characteristics and lesions may appear that specifically affect the skin or are possible indications of disease involving other organs or tissues. 

The generic term dermatitis indicates a large number of different skin manifestations, usually due to inflammation and characterized mainly by erythema, redness of the skin, itching, swelling, and peeling of the skin. The causes can be multiple, such as:

  • an infection
  • an allergic reaction
  • contact with an irritant
  • excessive dryness of the skin.


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