In the scientific work were used: morphological (preparation, microscopic, ultramicroscopic, morphometric), biochemical (determination of hemoglobin, glucose and glycosylated hemoglobin in the blood), experimental (reproduction of the model of streptozotocin-induced diabetes mellitus) and statistical methods that allowed to establish the features of vascularization in the norm and patterns of qualitative and quantitave changes in the links of the hemomicrocirculatory flow and tissues of the lips and mucous membranes of mouth angle in the rats in normal and experimental diabetes mellitus. The author independently performed the fragment of study on the structure of the mucosal system of the lip and the mucous membrane of mouth angle in the rats in normal and experimental diabetes mellitus. Results of investigation give us the opportunity to determinate primary changes and dynamic of their progression of the lip and the mucous membrane of mouth angle in order to understand at which period of the experimental streptozotocin-induced diabetes, pathomorphological changes become irreversible. The first morphological manifestations appeared at the end of the second week of diabetes in the form of thickening of the epithelial plate, in the basal and spinous layers mark epitheliocytes with swollen cytoplasm and scapularly modified basophilic nuclei. It also gives reason to say that every week of the chronic experimental streptozotocin-induced diabetes, is a kind of unfavorable period along which at the tissues of the lips and mucous membranes of mouth angle and links of their hemomicrocirculatory flow changes are appeared. After four and six weeks, the epidermal cell nucleus stained part of the cells intensely basophilically with heterochromatin predominance in the karyoplasm. The veins and venules of the mucosa are enlarged, the blood-filled glands and the thinned wall. Adventitia and perivascular edema are observed. The lumen of the arteries and arterioles is not wide. The endothelial cells are located in the form of a wavy strip. Blood capillaries also have uneven gaps. At the ultrastructural level of the nucleus of long-form epitheliocytes with karyolema invaginations. In the cytoplasm, organelles are swollen, hypertrophied, and others are reduced in size. This afterword creates favorable pathomorphological foundation on the base of which dystrophic changes are leading for development ulcers, cheilitis and chronical cracks of mucous membrane of lips and mouth angle, which manifested by dysfunction and during long term period might become malignant. At the end of the eighth and tenth weeks of the study, there were changes in the mucous membrane of the lip with signs of increased sagging. The cytoplasm of endothelial cells is swollen. The basement membrane is heterogeneous in thickness, has significantly thickened areas, loses clarity. The veins and venules of the mucous membrane of the lip and the corner of the mouth are characterized by significantly enlarged, blood-filled gaps and a thin wall. Hemocapillaries with narrow lumps, thickened wall, significant perivascular and vascular connective tissue edema around the vessels. The arteriolar expansion was observed morphometrically to (22,12±0,08) μm; the diameter of the precapillary arterioles up to (11,33±0,11) μm; and a pronounced narrowing of the capillary diameter, which is (4,69±0,09) μm; however, the diameter of the capillary venules is (14,78±0,11) μm and the diameter of the venules is (27,65±0,11) μm, undergoing expansion, at the end of experiment statistically significant changes were observed in all indicators (p<0,001). The established reorganization of epitheliocytes is associated with trophism and the impact of metabolic processes. The manifestations of renewal, reparative regeneration is minor and require correction. Results of study have practical aspect of new methods of treatment, preventive health care and diagnostics methods for patients with diabetes for morphologists, pathomorphologists, dentists and periodonthologists. Key words: lip, oral mucosa, streptozotocin, diabetes mellitus, hematocirculatory blood flow, white rat. Branch-Medicine.
