The skin

The skin is the largest organ of the body, with an average surface area of 1.6 m2 and a weight of approximately 4 kg.

Skin functions

One of the most important functions of the skin is to act as a barrier against external agents such as bacteria and chemicals.

Another important function is to maintain body temperature. It is an organ with thermoregulatory capacity thanks to the action of the blood vessels.

  1. Protective barrier: acts against mechanical, chemical and pathogenic aggressions. It has the ability to destroy bacteria, absorb and eliminate liquids.
  2. Regulates temperature: when exposed to cold, the blood vessels prevent the blood from coming into contact with the skin and thus maintain the temperature.
  3. Prevents water loss and water entry: it acts as a hydro-electrolyte balance, maintaining the balance of body fluids and preventing water loss.
  4. Absorbs and filters radiation: the skin has the capacity to produce melanin, which allows it to act against ultraviolet rays.
  5. Vitamin D metabolism. The skin is the main source of vitamin D, from exposure to ultraviolet radiation.
  6. It has sensitive and cosmetic functions: skin is capable of showing reactions to our emotions. In addition, it transmits through receptors and nerve endings, touch and other sensations.

Dermatology is the branch of medicine that deals with the study of the skin.

Dermatology professionals study, diagnose and treat skin pathologies or diseases.

Skin care

Our skin is the largest organ of the body and has an important protective function. It protects us from external elements, such as the sun’s rays, wind and pollutants, as well as regulating our body temperature and helping to eliminate waste through sweat. It also helps us to interact with the world, as it allows us to feel touch and sensations.

However, our skin is also exposed to many factors that can damage it and cause it to age prematurely. Sun exposure, smoking, excessive alcohol consumption, poor diet, lack of sleep and stress are just some of the factors that can have a negative effect on our skin.

Therefore, adopting healthy habits to care for the skin is essential to keep it healthy and youthful. This includes wearing sunscreen every day, quitting smoking, limiting alcohol consumption, getting enough sleep, eating a balanced and healthy diet, and having a skin care routine that includes cleansing, toning and moisturizing the skin daily.

In addition, it is important to remember that the skin also needs internal protection. Drinking enough water to keep skin hydrated is crucial for healthy skin. It is also important to reduce stress, as stress can negatively affect the skin and worsen skin problems such as acne and eczema.

Skin structure

The skin is composed of three layers, which in turn are made up of several layers.


It is the most superficial and visible layer of the skin, with a thickness between 0.1 mm and 4 mm.

The epidermis is composed mostly of keratinocytes, which are segmented in the stratum corneum, in addition to melanocytes, responsible for the production of melanin, which is the pigment that tans us and protects us from the sun’s UV radiation.

The epidermis has a protective function, preferably. It is made up of:

  • Basal layer: the deepest layer and where keratinocytes are produced.
  • Spinous layer: it is at this point that keratinocytes produce keratin.
  • Granular layer: keratinization occurs.
  • Stratum lucidum: a transitional layer, formed by homogeneous cells without nucleus.
  • Stratum corneum: the most superficial layer of the epidermis, it is formed by keratinized cells that form a barrier against external agents and the loss of body fluids.


It corresponds to the middle zone and is the most important layer of the skin. It has a thickness between 0.3 and 4 mm.

It supports the epidermis with its collagen and elastin network, which is embedded in a gelatinous structure corresponding to polysaccharides (GAGs).

In addition, the dermis contains different elements, such as blood vessels, fibroblasts (cells), nerves, sweat and sebaceous glands.


It is the deepest layer and is rich in fat and connective tissue. It acts as a support for the dermis and is mainly responsible for regulating temperature.

Commitment to quality

This text on skin has been written by professional editors and reviewed by Sisneo’s medical-aesthetic team. In addition, we have relied on experts in medicine, engineering and aesthetics as a source of information, as well as specific studies to maintain the quality of what we publish.

At Sisneo Bioscience we are committed to publish truthful and contrasted information. And to update or correct it as soon as new knowledge becomes available.

Among others, we have used the following references:

  • Baumann L. «Skin ageing and its treatment» en J Pathol. 2007;211(2):241-251. doi: 10.1002/path.2098.
  • Ruiz Martínez, Mª Adolfina, & Morales Hernández, Mª Encarnación. (2015). «Aproximación al tratamiento del envejecimiento cutáneo» en Ars Pharmaceutica (Internet), 56(4), 183-191.