Muscular-aponeurotic system of the face

Mimic facial muscles, strictly speaking, no longer refer to the skin. But as these, the muscles make a significant contribution to the age-related skin changes and since recently there have appeared cosmetic products 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 the English literature it is called the superficial musculoaponeurotyc system (SMAS), a superficial muscular-aponeurotic system) that is "sewn" to the skin (but not to the bones) in several places. Cutting, the muscles pull the skin behind them, as a result of which the facial expression changes - the eyebrows frown, the forehead is wrinkled, the lips are stretched in a smile, etc. Although such anatomy provides all the richness and diversity of human facial expressions, it also creates the prerequisites for the formation of wrinkles and folds on the skin - firstly, the muscles in the contraction constantly stretch the skin, and secondly, because the muscular aponeurotic layer is not connected with the bones of the face, the skin will sag under the effect of gravity over the years.  

Fibroblasts are the most numerous cells of the dermis and its only "residents" (that is, they are constantly present in it). These are elongated cells with numerous processes, actively producing and secreting various connections, incl. Connective tissue fibers. Once the connective matrix around the fibroblast has formed, the "immature" active fibroblasts are transformed into "mature" inactive fibroblasts. Nevertheless, in response to damage, the fibrocyte returns to the active state and again begins to synthesize intensively. The subcutaneous adipose tissue of an adult is represented by a white fatty tissue. In white adipose tissue, mature adipocytes have one large fat drop (fatty vacuole), which can occupy up to 95% of the cell volume. Adipocytes of brown adipose tissue have many fatty vacuoles. Brown fatty tissue occurs in newborns and animals. It is believed that it plays an important role in the thermoregulation of the body. In adipose tissue there are many blood vessels, it is necessary to quickly "eject" fats into the blood or, conversely, to "capture" fat from the general circulation.

So, the arteries of the skin form a network under the skin, from which branchlets lead to the skin. Directly on the border of the dermis and hypodermis (fatty layer) they rejoin and form a second network. Vessels that feed the hair follicles and sweat glands leave it. All skin is permeated with very small vessels, which again often connect with each other, forming networks in each layer of the dermis. Some networks serve food purposes, others work as heat exchange structures. The features of the blood movement along 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 go from arterial vessels to venous, bypassing the areas where it should give nutrients and oxygen to cells. Perhaps the cosmetic effect of the massage can partly be explained by the fact that the massage activates the movement of the blood, causing it to run through all the vessels, "not cutting corners", which prevents shortage of blood supply. The rate of wound healing also depends on the intensity of the circulation. Where blood circulation has been disturbed for some reason, long healing ulcers can form on the site of wounds. Based on this, it can be concluded that the skin renewal rate, which is very similar to the wound healing process, will also depend on the circulation of the blood. The lymphatic system is closely connected with the circulatory system, the vessels of which also form in the skin of the network and intricate plexuses.

The skin vessels carry nutrients into it. At the same time, it is already known that the skin can transform proteins, fats and carbohydrates, destroying them into constituent parts with special enzymes and building the necessary structures from the resulting material. However, does this mean that the skin can be "fed" from the outside, spreading oil on it, like a sandwich? Interesting question - can the skin remove toxins? In foreign literature, it can sometimes be found that skin, unlike kidneys and liver, is not a secretory organ, and one should not expect "toxins" or "wastes" to come through it. However, there is evidence that the skin can delay and bind toxic metabolites, protecting other organs from their damaging effects, and also removing many metabolic products from the body. Due to its ramified 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).

[1], [2], [3], [4], [5], [6]