- Insufficient sebaceous secretion and / or dehydration of the horny layer.
- It is especially common in women.
- Causes: inherent to the person or by external factors, which alter the skin barrier.
- Integrity of the horny layer.
the main barrier
The skin constitutes the largest organ in the human body, with a surface area of nearly 2m² and a weight that represents approximately 6% of total body weight.
The skin separates the external environment from the body’s internal environment, but this separation is not isolating, because interchanges take place between external agents and the bodily functions that contribute to shaping the appearance of the skin.
1. BLOOD VESSELS
The blood vessels of the dermis are fine capillaries that come from the medium-sized vessels of the hypodermis.
The blood vessel network of the dermis not only supplies oxygen and nutrients to the cells and the structures located in this layer, but also nourish the cells of the epidermal layer that lacks blood vessels.
The dermis performs a fundamental role in the regulation of body temperature, in which the blood vessels and sweat glands participate.
Innervation of the skin
2. INNERVATION OF THE SKIN
Two types of nerve fiber can be found in the dermis:
The motor nerves:innervate the blood vessels,
the glands and the hair erector muscle.
The sensory nerves: are free or encapsulated nerve endings that act as heat, touch and pain sensory receptors.
The stimuli received by the skin’s surface are captured by the receptors of the dermal nerve endings, that transmit this information to the brain, which returns it processed in the form of a response.
3. SKIN APPENDAGES
The skin appendages are epidermal formation of the skin. There are three different groups:
Pilosebaceous unit: an anatomical and
functional unit consisting of the hair and its appendages; sebaceous gland, apocrine
sweat gland and arrector pili muscle.
The apocrine sweat gland.
Structure responsible for protecting the body from external agents:
Physical: solar radiations, injuries,
Chemical: penetration of substances.
Biological: pathogens (bacteria, fungi, etc.).
Protective function against the loss of water, preventing the dehydration of the skin by:
Keratin formation or keratinization.
Melanin synthesis or melanizatio.
Its function is to give the skin strength and elasticity. Through it run blood and lymphatic vessels, the skin appendages are found implanted in it, as are the sensitive receptors of the skin. Formed by connective tissue, it is comprised of:
Skin cells: Fibroblasts, histiocytes, mast cells, capable of engulfing and developing a response against foreign agents, protecting the dermis against microorganisms.
Dermal fibers: collagen, elastic and reticular, they make up 90% of the structure of the dermis.
Variant of the connective tissue that is known as adipose tissue. The abundance of subcutaneous fat tissue varies depending on the area of the body, gender and nutritional status, and there are two groups: Android (typical of men) and gynecoid (typical of women)
Protective: cushions impacts, shocks, etc.
Metabolic: the adipose panicle is a store of energy.
Plastic: the hypodermic adipose tissue shapes the figure.
Thermoregulatory:the fat acts as thermal insulation.
Aging represents a set of transformations that take place as a consequence of the time lived and how it has been lived. Skin aging is a reflection of the biological age, which does not always correspond with the chronological age and becomes apparent over the years through the visible signs that are: wrinkles, flaccidity or spots.
Depending on the combination of genetic factors and external factors, the process of aging will be more or less noticeable.
The Glogau scale to classify the degree of aging, takes into account aspects such as the chronological age and the influence of photoaging, to determine at what stage of aging we are and to establish the appropriate guidelines for care.
Melasma or cloasma is an acquired hypermelanosis that manifests in areas exposed to the sun, particularly the face. They are dark brown spo