Adipose tissue: anatomy and metabolism

Types and patterns of fat tissue distribution

By location and metabolism, fat tissue is divided into three main types: 1) subcutaneous fatty tissue; 2) deep (subfascial) fat layer and 3) internal (visceral) fat, located mainly in the abdominal cavity. The thickness and ratio of these three layers are extremely diverse, differ significantly in different parts of the body and largely determine the contours of the human figure.

The location and architectonics of fat deposits depend on many factors (heredity, sex, age, average metabolic rate, etc.) and are characterized by the following main regularities.

• The subcutaneous layer of fatty tissue exists in all anatomical zones and determines, first of all, the smoothness of the outline of the human body. Its thickness is largely determined by the individual ratio of energy input and energy consumption and in the vast majority of cases it is relatively easy to reduce by physical exercises and (or) reducing the overall energy value of the food ration.
• A deep subfascial fat layer is expressed only in some anatomical zones (abdomen, thighs, submental region) and determines individual differences in the contours of the figure, as well as the volume and contours of various areas of the human body. Fat deposits of the deep layer have a special tissue metabolism, and their localization and volume are more firmly fixed genetically and relatively little change when people lose weight.
• Excess fatty deposits by the male type are characterized by:
  • relatively uniform increase in the thickness of the subcutaneous fat layer of the limbs and chest;
  • a more significant increase in the volume of the abdomen, mainly due to visceral fat deposits with a relatively small thickness of the surface and deep layers of the anterior abdominal wall;
  • frequent presence of fatty "traps" in the flank area and in the submental zone.
• Excess fatty deposits by female type are characterized by a local increase in the volume of a predominantly deep layer of adipose tissue in the thigh, inner surface of the knee, abdomen and - more rarely - on the face, arms and lower leg.

Types and forms of fat deposits

At the heart of the increase in the volume of adipose tissue is the hypertrophy of fat cells (adipocytes). This process can occur in the fat tissue of any localization and leads to the development of two main forms of fat deposits: 1) local and 2) general (generalized).

Local forms of fat deposits

Local hypertrophy of fat cells can arise due to their genetically determined hypersensitivity to the incoming glucose. There are three main forms of local distribution of fatty deposits:

• fatty "traps" (a delimited form);
• diffusive-local form;
• finely irregular contour irregularities.

Fat "traps" are characterized by relatively clear boundaries of body contour changes due to hypertrophy of adipocytes of deep or superficial layers of adipose tissue. The greatest importance in this case is the hypertrophy of the deep layer.

Diffusive-local form of fatty deposits is characterized by a pronounced increase in the predominantly surface layer of fatty tissue in a certain anatomical region. In this case, the contours of this section are outlined indistinctly and smoothly pass into adjacent zones with a normal thickness of the fat layer.

Most often, the zones of diffuse increase in the thickness of the fat layer are located on the front surface of the thigh and in the epigastric region, less often on the hind and thigh.

Small-hummock contour infringements are caused by the expressed hypertrophy of the adipocytes of the subdermal layer and are found both in local and in generalized forms of fatty deposits. The development of this condition is largely due to the inherent peculiarities of adipocyte metabolism of the superficial fat layer, and is also due to the anatomical structure of the subcutaneous fatty tissue. In particular, the subdermal layer contains connective tissue bridges that connect the dermal layer of the skin with the superficial fascia and provide both fixation and skin mobility with respect to the deep tissues. In some people with a low threshold of elasticity of connective tissue bridges hypertrophy of adipocytes leads to bulging of adipose tissue towards the skin with the formation of an uneven contour in the form of small tubercles on the surface of the skin. This condition is often called cellulite, which, from the point of view of medical terminology, is incorrect, since the end of "it" is used to describe the inflammatory process. It is more appropriate in this case to use the term "finely chalky lipodystrophy".

The peculiarity of all local forms of obesity is the relative stability of their volume and shape, which can persist even with significant weight loss.

The generalized form of fatty deposits (obesity)

According to modern ideas, the general obesity is the result of the energy imbalance that occurs when the amount of incoming energy exceeds the energy expenditure of the organism. Excess energy leads to the deposition of an additional volume of adipose tissue. In this case, hypertrophy of fat cells both surface and deep layers occurs. With pronounced obesity, the thickness of the adipose tissue becomes significant, and the contours of fatty "traps" cease to be clearly defined.

Such changes in adipose tissue often occur in adulthood and are subject to predominantly conservative treatment. At the same time, according to a study by N. Greenwood (1985), fat cells can form throughout life. The increase in fat mass due to both hypertrophic processes and the increase in the number of cells is unfavorable for the prognosis of conservative treatment.

Effective correction of the figure in these patients is possible with the help of liposuction, which leads to the removal of excess fat cells.

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