Hypothermia is a situation in which the internal body temperature drops below 35 degrees Celsius. The article presents the relevance, theoretical aspects and features of the action of general hypothermia on the heart in general and cardiomyocytes in particular. The purpose of the study was to study the changes in the myocardium under the action of general hypothermia at different levels of structural organization. The object of the study were the hearts of laboratory adult rats. The study involved 20 animals. The longitudinal section shows that the right ventricle is much thinner than the left and its cavity is presented in the form of a crescent. The interventricular septum is thicker than the wall of the right ventricle and goes into its cavity. Results. To establish the shape of the heart and track the dynamic changes at the organ level, we calculated an index showing the ratio of the width of the heart to its length. In 80% of cases, the heart shape of intact rats was conical, the index averaged 55%, only 20% elliptical, the index was more than 65%. We did not observe other forms of heart in the group of intact rats. In the experimental groups, a spherical heart shape appeared. The thickness of the anterior wall of the left ventricle for 10 days from the beginning of the experiment was 3.15±0.11 mm, the side wall 3.1±0.11 mm, the posterior wall 2.45±0.04 mm, interventricular septum 2.95±0.09 mm. In the right ventricle, the thickness of the anterior wall is 1.04±0.03 mm, the posterior wall is 1.36±0.04 mm. On the 30th day from the beginning of the experiment, the thickness of the anterior wall of the left ventricle was 3.21±0.11 mm, the side wall 2.65±0.06 mm, the posterior wall 3.27±0.09 mm, the interventricular septum 3.14±0.13 mm. In the right ventricle, the thickness of the anterior wall is 1.09±0.04 mm, the posterior wall is 1.38±0.03 mm. Conclusions. The increase in heart mass, change in its shape due to changes in the middle third of the heart wall of both the left and right ventricles. The highest rates were in the middle third of the heart (zone "B"): In all layers of the myocardium there is an increase in the diameter of cardiomyocytes, a decrease in the distance between individual cardiomyocytes and their groups. The distance between adjacent cardiomyocytes in the left ventricle is: in the outer layer 1/8 of the diameter of the cardiomyocyte, between groups of cardiomyocytes 1/4 of the diameter of the cardiomyocyte
Keywords: myocardium, hypothermia, morphometry
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