The respiratory system is one of the most important systems that carries out the body's gas exchange between air and blood, as a result of which oxygen enters the body and carbon dioxide is removed from it to the environment. In recent years, in the list of diseases of various etiologies, there has been a sharp increase in the number of diseases related to the respiratory organs. There is no doubt that the effective treatment of these pathologies is impossible without knowledge of breed and species characteristics of the anatomy and histology of respiratory organs, the morphofunctional parameters of which should be taken into account when carrying out diagnostic and preventive measures, regarding the prevention of animal diseases, and when providing them with medical care. Therefore, when planning research on the respiratory organs, which include the lungs, one should take into account their topographical-anatomical specific features in domestic animals, their structural-functional features of the microscopic structure, etc. The completed morphological work is a fragment of the research topic of the Department of Normal and Pathological Morphology, Hygiene and Expertise, Polis National University: "Development, morphology and histochemistry of animal organs in normal and pathological conditions", (state registration number – No. 0113V000900). This publication is devoted to the study of the morpho-functional characteristics of the lungs of a sexually mature horse (Equus Feruscaballus L., 1758). Using the method of anatomical dissection, macroscopic, histological, morphometric and statistical methods of research, the macro- and microscopic structure of the lungs was clarified and their belonging to a certain anatomical type was determined. As a result of the conducted studies, the partial structure of the lungs was determined, their topography, shape, dimensions, absolute and relative mass of the lungs were determined, a morphometric assessment of their morphological structures, asymmetry coefficient, etc. was carried out. Staining of tissue sections with hematoxylin and eosin was used to study cell morphology, conduct morphometric studies, and obtain histological examination preparations. When conducting morphological studies, the basic rules of good laboratory practice GLP (1981), the provisions of the "General ethical principles of animal experiments" adopted by the First National Congress of Bioethics (Kyiv, 2001) and the requirements of the "Rules for conducting work using experimental animals", approved by order of the Ministry of Health No. 281 dated November 1, 2000 "On measures to further improve organizational forms of work with the use of experimental animals". It was morphologically investigated that the macro- and micromorphology of the lungs of a sexually mature horse has certain characteristic morphological features, according to the class, age and species of animals. Thus, through scientific studies of the horse, we present the presence of individual morphological features in the lobular structure of the lungs. So, in the left lung of horses there are only two lobes: cranial and caudal, in the right lung there are three lobes: cranial, caudal and additional. Histological structure of acini formed by alveolar ducts, alveolar sacs and alveoli. According to the results of morphological studies, the alveolar tree in horses, represented by a shortened type, is wide and has a bubble shape. Morphometric studies have shown that the average volume of pulmonary alveoli in clinically healthy horses is 699.8±106.42 thousand μm3. The respiratory part of the lungs in horses occupies 54.8±7.4% of the total area of the lung parenchyma, the connective tissue base – 45.2±7.4%.

Key words: anatomy, domestic animals, respiratory organs, gas exchange, morphometry, morphotopography, lung lobes, absolute weight, lung histostructure, bronchial tree, respiratory bronchioles, lung asymmetry.