The musculoaponeurotic system of the face

The facial muscles, strictly speaking, are no longer considered skin. But since these muscles make a significant contribution to age-related changes in the skin and since cosmetics have recently appeared that affect them, we will consider them. A distinctive feature of the facial muscles is that they are fused into a single muscular-fibrous layer (in English literature it is called the superficial musculoaponeurotyc system (SMAS) - superficial muscular-aponeurotic system), which is "sewn" to the skin (but not to the bones) in several places. When the muscles contract, they pull the skin along with them, which changes the facial expression - the eyebrows frown, the forehead wrinkles, the lips stretch into a smile, etc. Although such anatomy provides all the richness and variety of human facial expressions, it also creates the prerequisites for the formation of wrinkles and folds on the skin - firstly, when the muscles contract, they constantly stretch the skin, and secondly, due to the fact that the muscular-aponeurotic layer is not connected to the bones of the face, the skin sags over the years under the influence of gravity.

Fibroblasts are the most numerous cells of the dermis and its only "residents" (i.e. they are constantly present in it). These are elongated cells with numerous processes that actively produce and secrete various compounds, including connective tissue fibers. As soon as the connective matrix around the fibroblast has formed, the "immature" active fibroblasts turn into "mature" inactive fibrocytes. However, in response to damage, the fibrocyte returns to an active state and again begins to synthesize intensively. The subcutaneous fat tissue of an adult is represented by white adipose tissue. In white adipose tissue, mature adipocytes have one large fat droplet (fat vacuole), which can occupy up to 95% of the cell volume. Adipocytes of brown adipose tissue have many fat vacuoles. Brown adipose tissue is found in newborns and animals. It is believed that it plays an important role in the body's thermoregulation. There are many blood vessels in adipose tissue, this is necessary for the rapid "release" of fats into the blood or, conversely, for the "capture" of fat from the general circulation.

So, the skin arteries form a network under the skin, from which branches extend into the skin. Directly at the border of the dermis and hypodermis (fat layer) they reconnect and form a second network. Vessels extend from it, feeding the hair follicles and sweat glands. The entire skin is penetrated by very small vessels, which again often connect with each other, forming networks in each layer of the dermis. Some networks serve the purpose of nutrition, others work as heat exchange structures. The features of blood movement through all these blood labyrinths with numerous transitions between branches are still poorly understood, but there is an opinion that the skin is prone to "starvation" due to the fact that blood can move from arterial vessels to venous ones, bypassing the areas where it should give nutrients and oxygen to the cells. Perhaps the cosmetic effect of massage can be partly explained by the fact that massage activates blood flow, forcing it to run through all the vessels, "without cutting corners", which prevents a deficiency of blood supply. The speed of wound healing also depends on the intensity of blood circulation. Where blood circulation is impaired for some reason, ulcers that do not heal for a long time can form at the site of the wounds. Based on this, we can conclude that the speed of skin renewal, which is very similar to the process of wound healing, will also depend on blood circulation. The lymphatic system is closely connected with the circulatory system, the vessels of which also form networks and intricate plexuses in the skin.

The skin vessels carry nutrients into it. It is already known that the skin can transform proteins, fats and carbohydrates, breaking them down into their constituent parts with special enzymes and building the structures it needs from the resulting material. However, does this mean that the skin can be "fed" from the outside, spreading oils on it, like on a sandwich? An interesting question - can the skin remove toxins? In foreign literature, one can sometimes find statements that the skin, unlike the kidneys and liver, is not an excretory organ, and one should not expect "toxins" or "slags" to be released through it. However, there is evidence that the skin can retain and bind toxic metabolites, protecting other organs from their damaging effects, and also remove many metabolic products from the body. Thanks to its extensive vascular network, the skin also participates in gas exchange, releasing carbon dioxide and absorbing oxygen (the skin provides 2% of the body's gas exchange).

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