Features of the microscopic structure of the lungs of Clarias gariepinus of the catfish family

The vital activity of living organisms is essential for providing cells and tissues with oxygen and nutrients and the excr e tion of metabolic products. The body's response to environmental influences, uniting all organs and systems into a single whole, requires the regular morphofunctional activity of all body systems, including the respiratory system, which served as the purpose of the research. Using macro- and microscopic, morphometric, and statistical research methods, the results are presented on the microscopic structure of the lungs of the catfish species Clarias gariepinus (Burchell, 1822). Thus, in the gas exchange system of birefringent fish, represented by the C lari a s catfish, changes occur in the process of their phylog e netic development (two circl uits of blood circulation are formed), which are characteristic of amphibians, in which, in add i tion to gills, paired lungs are also formed, thanks to which animals can breathe atmospheric air. The lungs of the C lari a s catfish are formed by branched anatomical structures located on the second and fourth- lung arches. These are paired pale pink morphological structures with cellular walls connected to the esophagus. The medial and lateral lobes form the right and left lungs: starting from the gill cavities, the main trunk of the medial lobe of the lungs branches out like a tree into four large branches, which are divided into medium and small, giving rise to thick-walled alveoli. The lateral lobe of the lungs begins with a separate trunk that is not connected to the m e dial lobe of the lungs. The lungs of C lari a s catfish are covered with a connective tissue membrane (pleura), which is microscopically formed by three layers: outer, middle, and inner. The micr o scopic structure of the wall of the bronchi of the lungs is built of three membranes – outer, middle (muscular), and inner: the surface of the wall of the outer membrane is formed by epithelial cells that form elongated villi, the lamina propria of the membrane is formed by loose connective tissue, in which a network of blood vessels is located; the muscular membrane of the wall is formed by transversely striated muscle tissue, the fibers of which have a longitudinal direction; the inner me m brane is thin and formed by elongated epithelial cells. The cavity of the bronchi, throughout the entire interval of the bronch i al tree, ending in the pulmonary alveoli, is filled with reticular tissue. According to morphometric studies, the most prom i nent morphometric parameters (wall thickness, thickness of the bronchial cavity) are characteristic of the large, then the medium, followed by the small bronchi. Pulmonary alveoli have a rounded shape; microscopically, a significant network of vessels (capillaries) of the microcirculatory bed is detected in the wall of the connective tissue membrane.