Fig. 2.

Five cross-sectional layers of myocardial tissue from exterior to interior. The first layer is fibrous pericardium consisting of fibroblasts that can secure the heart's anatomical position. The second and third layer is both serous pericardium, which can lubricate mechanical force of myocardium. The forth layer is the thick myocrdium consisting of active cardiomyocytes and supportive blood vessels. The fifth layer is the robust endocardium that has endothelial trabeculae in order to increase pumping force and area inside. Each layer of myocardial tissue is physically and orderly bond by the components of ECM.