The purpose of our study was to determine the ultrastructural peculiarities of the haemomicrocirculatory pathways of the aortic walls of the albino rat in the norm and in the course of experimental diabetes mellitus (DM). Materials and methods. Using the method of electron microscopy, it was established that the aortic wall is composed of three tissue layers: the inner layer represented by the endothelial cells, the sub-endothelial layer, and the internal elastic membrane; medial layer which consists of the external elastic membrane/lamina; and the external (outer) layer -adventitia. The latter is formed by the loose fibrous connective tissue with a small amount of collagen fibers, muscle cells and macrophages. Haemomicrocirculatory pathway vessels (HPV) start from the blood vessels located in the adventitia, penetrate the outer third of the medial layer and branch out between the outer and medial layers of the aortic wall. Results and discussion. The first ultrastructural changes in the organization of the aortic wall and its parts of the HPV are observed after two weeks of the onset of streptozotocin induced diabetes and are gradually increasing with time. Destructive changes in diabetes are manifested by the restructuring of the ultrastructure of all layers of the aortic wall. The question "to be or not to be" for atherosclerosis is predetermined by the interaction of dislipoproteinemia of an atherogenic nature with the vascular wall. Endothelium plays an important role in these processes. Complex functional-adaptive features of the endothelium provide support of vascular homeostasis at a certain level and prevent damage to cells and fibers. Loss of these mechanisms leads to a violation of the vessel's permeability, namely, by the components of plasma, and the development of atherosclerosis or arteriosclerosis, depending on the factor causing this damage. One of the key issues in the pathogenesis of atherosclerotic lesions of the vascular wall in diabetes is the analysis of the mechanisms and routes of transport of atherogenic lipoproteins in the vascular wall through the endothelium, which acts as the only cell barrier between blood plasma and intima of the vessel. Studying the ultrastructure of the elastic component of the aorta medial layer, there was observed a loss of normal elastic architecture of the aortic mediums. Conclusions. Disorganized and disordered elastic fibers were found that linked the lumbar units, which caused a local weakening of the aortic wall. This work is the basis for further research of morphologists and clinicians regarding the development of new diagnostic, preventive and treatment methods for diabetic angiopathy in patients with diabetes. The study is a part of the research work of the Lviv National Medical University named after Danylo Halytsky on "Morphological peculiarities of the haemomicrocirculatory pathway of the aortic wall of the rat in norm and in experimental diabetes mellitus".
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