Дослідження є фрагментом науково-дослідної роботи «Особливості структурної реорганізації кровоносних русел внутрішніх органів за умов впливу екзо-і ендогенних негативних чинників у експерименті» (номер державної реєстрації 118U000360). © Morphologia.-2018.-Т. 12, № 3.-С. 44-50. © І.Є. Герасимюк, М.О. Вацик, 2018 v.marunka@gmai Herasymiuk I.E., Vatsyk M.O. Features of reorganization of blood vessels of lungs of rats at various degrees of total dehydration. ABSTRACT. Background. Water with substances in it dissolved is functionally the only system of the organism, which provides the implementation of homeostasis. The constant level of osmotic pressure of blood plasma, intercellular and intracellular fluid is one of the main conditions of the normal functioning of the organism. Violations of the hydro-electrolyte constant occur in the organism almost constantly, but sometimes they go beyond the average norms. One such manifestation is the lack of water in the body, which occurs as a result of a variety of physiological and pathological conditions. The immediate consequence of dehydration is a violation of peripheral blood flow with the development of circulatory hypoxia. Objective. The purpose of the study: to establish the peculiarities of reorganization of blood vessels of lungs of rats at various degrees of general dehydration and give them quantitative characteristics. Methods. Experiments were conducted on white laboratory sexually-mature male rats, which modelled the general dehydration of the lung of mild, medium and severe degrees. Histological and morphometric examinations of the blood vessels of the lungs were performed. Results. On the first day of the experiment, there was an increase in the blood supply of the lungs, which was confirmed by the tendency to expand the lumen of both pulmonary and bronchial arteries, which was confirmed by the decrease in their level of the functional parameter-the index of Vogwarts. However, in the following terms, there was an ascending vasoconstriction with a simultaneous decrease in the throughput of the arteries of the small and middle caliber and the enlargement of the lumen and the increase in the capacity of arteries of large caliber. The veins, on the contrary, gradually became anemic, what was accompanied by an increase in the tone of their walls and narrowing of the lumen, which often acquired a "star-like" deformation. With the increase in the observation period and, accordingly, the degree of general dehydration, the frequency of detecting arteries of the "closure" type increased. Conclusion. The results of the conducted research indicate that certain morpho-functional changes of hypovolemic nature gradually develop in the parenchyma of the lungs and their blood channels under the condition of general dehydration of the body, and their intensity depends on the duration of dehydration, and hence its degree.