COMPARATIVE FEATURES OF DIFFERENT TYPES OF MUSCLE TISSUE

Abstract

Muscle tissues are widespread in the human organism. Since their main feature is ability to contractility, their sarcoplasm (cytoplasm) contains a well-developed contractile apparatus, which can have its specific characteristics in different muscle tissues. Muscle tissues differ from each other not only in their localization and structural characteristics, but also in their origin, as well as their ability to regenerate. There are two main classifications of muscle tissues: morphological one taking into account the peculiarities of the structure of the contractile apparatus, and histogenetic one taking into account the origin of tissue. According to the morphofunctional classification, muscle tissues are divided into striated (cross-striated) and smooth. In turn, striated tissues are divided into skeletal and cardiac. The main tissue element of skeletal muscle tissue is myosymplast, which is formed during embryogenesis as a result of the fusion of myoblast cells. The main tissue element of cardiac muscle tissue are cells — cardiomyocytes, which during embryogenesis connect with each other to form fibers. The main tissue element of smooth muscle tissue are cells — smooth myocytes, which during embryonic development can migrate from different rudiments. Muscle tissue of internal organs and vessels has a mesenchymal origin, the muscles of the iris of the eyeball are neural, myoepithelial cells of glands are ectodermal. Despite the fact that the structure and origin of the muscle tissues are well studied, in recent years a lot of information has appeared from the field of molecular biology concerning their development in embryogenesis. In addition the issues of regenerative capabilities of different types of muscle tissues remain debatable. Skeletal muscle tissue shows the greatest regenerative abilities. Its regeneration is provided by satellite cells (myosatellitocytes), which isolate themselves on the surface of skeletal muscle fiber during intrauterine development, without fusing with it and preserving regenerative abilities due to the protein Pax7 expressed by myoblasts that are the precursors of myosatellitocytes. Until now, there is no unambiguous data on the regenerative capabilities of cardiomyocytes. There is controversial information in the literature about the possible role of cells c-kit+ as cardiac stem cells. However, they cannot provide full-fleged regeneration due to their small quantity in the myocardium. Smooth myocytes of blood vessels and internal organs are capable of reparative regeneration, which is provided by cells entering mitosis when smooth muscle tissue is damaged. But the question remains not fully clarified, which cells are capable of performing this function. Clarification of issues related to the regeneration of various types of muscle tissue may be of great importance for practical medicine.