Varieties of wrinkles and their causes

As is known, any type of aging has one common feature, skin wrinkling. That is why most methods of correcting age-related skin changes are directly or indirectly aimed at reducing the depth and severity of wrinkles. Moreover, many methods of assessing the effectiveness of certain methods of influence are based on assessing the state of the skin relief (the method of skin "prints"), counting the number and measuring the size of wrinkles.

There are different classifications of wrinkles. They are distinguished by their location on the skin of the face and neck (for example, wrinkles in the forehead, corners of the eyes, around the mouth, etc.), by the depth of their location (superficial and deep), and by the mechanism of formation (mimic or associated with a change in the tone of the facial muscles and gravitational ptosis of the soft tissues of the face, i.e. static). The chronological sequence of the formation of various wrinkles is well known. The first wrinkles, which can appear at the age of 20-25, are associated with constant contraction of the facial muscles. Over time, when the skin begins to suffer from chronological aging, both superficial and deeper wrinkles appear, associated with dehydration of the epidermis, thinning of the dermis and destruction of fibrous structures in it. Photoaging, potentiating the effect of chronological aging, contributes to even greater destruction of elastic fibers. The outcome of this process is the deepening of existing wrinkles and the appearance of characteristic wrinkling of the skin, especially noticeable in the area of the cheeks. Later, with hormonal changes against the background of a sharp decrease in the density of the dermis, a change in the tone of the facial muscles and gravitational ptosis of the soft tissues of the face and neck, deformation of the oval of the face, skin of the eyelids and other changes appear. This is accompanied by deepening of the nasolabial folds, the appearance of deep folds running from the corners of the mouth to the chin (the so-called "puppet mouth"), the cervical-mental fold and other wrinkles.

By now, information has been accumulated about the complex of morphological changes in the skin that occur during the formation of wrinkles. Knowledge of the mechanisms of wrinkle formation is necessary for a professional to resolve the issue of targeted complex correction of this phenomenon.

Mimic wrinkles

More than 19 muscles provide facial mobility during talking, chewing, opening and closing the eyes, smiling, frowning, etc. However, only certain movements of the facial muscles lead to the appearance of expression wrinkles. This occurs only in those places where the muscles are localized close to the overlying dermis. Such areas include typical oblique lines in the projection of "crow's feet" on the skin in the temporal regions, horizontal lines on the forehead, vertical lines between the eyebrows and oblique lines around the mouth. Until recently, it was believed that their appearance is associated exclusively with tightening of the dermis in areas of most frequent contraction of the facial muscles. Research in recent years has shown that expression wrinkles are formed not only under the influence of contraction of the underlying muscles, but also as a result of spontaneous contraction of dermal fibroblasts. It is known that a muscle cell is capable of contraction due to the presence of a special submembrane complex in it - a system of tonofibrils and tonofilaments. Tonofibrils include actin and myosin fibrils. When a nerve impulse affects a muscle cell, calcium ions leave the smooth endoplasmic reticulum (ER), and thus a biochemical reaction of actin and myosin interaction is triggered. The formation of the actin-myosin complex is accompanied by shortening of the muscle fiber due to the fact that actin filaments are "pushed" into myosin filaments and muscle contraction occurs. It has been shown that dermal fibroblasts are also capable of such contraction due to the presence of a small number of tonofilaments in them, compared to myocytes. The impulse for their contraction is transmitted from the contracting striated muscles of the face. Subsequently, calcium is released into the EPR, under the influence of which the fibroblast tonofilaments are subject to contraction. The contracted fibroblast pulls along a complex network of fibrous structures of the dermis and epidermis, the result of which is constantly increasing degenerative-dystrophic changes in these areas of the skin. Thus, it becomes clear that the mimic wrinkle is formed due to a kind of constant "mechanical stress" in the dermis. It is no coincidence that some researchers distinguish a special type of aging - myoaging.

The formation of superficial wrinkles is associated with superficial changes in the skin - at the level of the epidermis and upper dermis. Deep wrinkles are associated not only with superficial, but also with deeper changes - in the middle and lower thirds of the dermis. It is known that the normal pattern and texture of the skin surface are provided by a number of structures and physiological mechanisms. One of these mechanisms is maintaining a certain moisture content of the stratum corneum. It is known that on the skin surface under physiological conditions a delicate balance is established between the water content in the stratum corneum itself and in the environment. Changes in the synthesis and ratio of highly specialized lipids lead to a violation of the barrier properties of the skin and, consequently, transepidermal water loss. Dehydration of the stratum corneum leads to the appearance of superficial wrinkles. This phenomenon may occur at a young age with constant exposure of the skin to unfavorable environmental factors (low or high ambient temperature and humidity, other climatic factors), irrational skin care (aggressive detergents, alcohol-containing solutions, inadequate moisturizing, etc.), and also with some dermatoses (atopic dermatitis, ichthyosis, etc.). The changes occurring in the skin can be united by the general term - "delipidization". Dehydration of the stratum corneum, along with thinning of the epidermis, is also characteristic of menopausal aging. The main trigger for these changes is a slowdown in the proliferation of basal keratinocytes of the epidermis under the influence of a decrease in the concentration of estradiol. Changes in skin pattern, as well as superficial wrinkles can also be caused by uneven thickening of the stratum corneum. This phenomenon is typical of photoaging.

The composition of the main substance of connective tissue and fibrous structures of the dermis play a significant role in the appearance of wrinkles. Of course, the condition of these structures depends largely on the functional activity of dermal fibroblasts. At the beginning of the last century, scientists noted that the initial signs of age-related changes in the skin are interconnected with the destruction of elastic fibers, and more delayed ones - both elastic and collagen. Oxytalan elastic fibers are most sensitive to various trigger factors of the external environment, and they are the first to be destroyed. The consequence of this is superficial wrinkles. With the destruction of elaunin and mature (true) elastic fibers, deeper wrinkles are formed. It is known that after 30 years, elastic fibrous structures begin to undergo fragmentation and disintegration. In addition, with age, with the deposition of lipids in the dermis, the elastase enzyme is activated and starts the process of elastolysis, i.e. the destruction of elastic fibers. Elastic fibers are most vulnerable to ultraviolet rays, so the described changes are especially characteristic of photoaging.

As for the talc fibers, they provide the stromal framework and their bundles are arranged in different directions. Recent studies in the field of skin aging biology have shown that after 40 years, not only does collagen synthesis in dermal fibroblasts decrease, but the production of special enzymes by these cells, collagenases or matrix metalloproteinases (MMP), also increases. Collagenases, like elastases, promote the destruction of fibers. The outcome of these processes is that the skin loses elasticity and seems to "sag", and wrinkles deepen. This process is most noticeable in the deforming type of aging, when deep wrinkles appear, associated with changes in facial muscle tone and gravitational ptosis of soft tissues. Thus, any type of aging involves the destruction of dermal fibers.