[Architecture of the rat ventricular myocardium].

The working myocardium architecture was studied in heart ventricles of Wistar rats using the method of layer-by-layer dissection. Ventricle myocardium in the rat was found to be formed by three layers: superficial (subepicardial), middle and deep (subendocardial). The superficial and deep layers were present in both ventricles, while the middle one was found only in the left ventricle. The greatest variations were detected in the orientation of superficial layer muscle fibers: in the left ventricle subepicardial fibers had mainly a longitudinal arrangement, while in the right ventricle they were arranged transversely to the heart longitudinal axis. Most of the myocardial mass in the left ventricle, with the exception of the apex, was represented by a middle layer of circular fibers. In the deep layer, the fibers were oriented longitudinally, forming the trabeculae and papillary muscles.