The Human Skin

For many it is unknown that the skin is the greatest extension organ of the human body. It covers our entire body, measuring more than 2 m2, containing a variety of complex structures attached, including glands, hair and specialized sensory structures. This varies its thickness depending on its location and its weight in some cases exceeds 5 kg.

Functions of the skin

The primary function of this organ is to help maintain the structural integrity of the organism. Thermoregulatory, as well as serving as a protective barrier against external agents, facilitating the exchange of substances and the reception of external stimuli.

How is the skin structured?

This is a very complex organ and to facilitate its study, it has been divided into 3 main layers.

  • The epidermis, the outermost layer, it provides a protective barrier and creates the skin tone.
  • The dermis, below the epidermis, contains resistant connective tissue, hair follicles and sweat glands.
  • The deeper subcutaneous tissue (hypodermis) is composed of adipose and connective tissue

Skin layers

Over the years, methods have emerged to catalog it according to various criteria, one of which is the Fitzpatric scale. This scale classifies the skin according to the amount of melanin that it contains, a substance that besides being responsible for the color of our skin, protects the epidermis from the aggression of ultraviolet radiation.
The reaction is characterized fundamentally in 3 aspects, the degree of burn by radiation, the change in the tone (tanning) and the appearance of freckles. Reasons why it takes the name of:

Fitzpatrick scale of Skin Phototypes

PhototypeSkin colorResponse to UV irradiation
IWhite.In front of the sun exposure always burns
The skin never tans.
Usually has many freckles.
IIWhiteFaced with sun exposure always burns.
Skin tans with difficulty
Usually has a lot of freckles.
IIIBeigeFaced with sun exposure sometimes mild burns.
The tanning tone that the skin can acquire is medium
Few freckles
IVBrownFacing sun exposure rarely burns
Skin tans easily.
They do not have freckles.
VDark brownFacing sun exposure rarely burns
Skin tans very easily.
They do not have freckles.
VIBlackNever burns
Skin tans very easily
They do not have freckles.

Studies show that the chances of developing a skin cancer or other skin malignant disease decrease as the phototype increases.

Another way to facilitate its classification, in this case oriented to cosmetology and skin care, is the classification in biotypes, according to the balance between sweating and the sebaceous secretions of the skin.

How are cutaneous biotypes classified?

The classification of the different cutaneous biotypes is related to the sudoral and sebaceous secretions that form the hydrolipidic mantle.
These constitute a natural layer, in which there is a secretory balance optimum that gives the skin surface a state of lubrication and regulated humidification.

The sudoral secretions are composed of sodium chloride, potassium, urea, ammonia, lactic acid and proteins, providing the water portion to the mantle hydrolipidic my entras that sebaceous secretions constituted by ceramides, cholesterol, free fatty acids and remnants of the epidermal keratinization process they make up the lipid portion of it. When this balance is altered, distinguish the different types of skin.
It should be considered that in addition factors are inherent to the individual and
environmental factors that substantially modify their characteristics, translating into the multiplicity of biotypes that exist.

From the cosmetic point of view the following cutaneous biotypes can be distinguished:

Skin Biotypes

  • Normal skin:

It is one that is in perfect sebaceous secretory balance and sudoral It presents a smooth surface, soft to the touch, of uniform color, with moderate brightness, absence of unattractive aspects and poorly visible pores.
The hydration  is perfect and is regulated by the biological activity of the basal layer. The deeper layers are balanced and active preventing the formation of wrinkles. Tolerates soaps well, does not flake and resists extreme temperatures.

  • Dry skin:

The skin may be dry due to the absence of fat or loss of water. Often these states coexist. They are very thin, tense and striated, reactive to external stimuli, tending to present telangiectasias. It is not very elastic, with matt coloration and imperceptible pores. It is characterized for being opaque, without shine, rough, fine desquamation, little elastic and with tendency to wrinkles.

  • Oily skin:

They have a thick texture, pilosebaceous follicles dilated, unctuous, moist and well hydrated. The probability of the appearance of wrinkles decreases, while the predisposition to the appearance of comedones increases. Resist the action of external agents due to the permanence of the sebaceous secretion. Seborrhea is located in the so-called physiological seborrheic regions, scalp, centrofacial, centrotrophic area and interscapular.

  • Mixed skin:

It is the coexistence of different skin types in the same individual.
Example, dehydrated seborrheic skin presenting oiliness in the central zone of the face or zone “T” and dryness in cheeks and laterals.

  • Sensitive skin:

It presents reactions by contact more easily than the rest of the people.


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