Myoarchitecture of the ventricle. (A,B) Cross‐section showing the net‐like arrangement in the trabeculated myocardium of low‐weight specimens of group 1. (C,D) Cross‐section showing the net‐like arrangement in the trabeculated myocardium of specimens of groups 2 and 3, respectively. (E) Sagittal histological section showing the lacunae opening from the lumen and the microlacunae connecting the individual trabeculae. (F) Organization of the outer compact layer under the subepicardium, involving the inner spongy layer. Note the cardiomyocytes arranged longitudinally. (G,H) Group 3. (G) Sagittal histological section showing coronary vessels in the subepicardium, penetrating the outer compact layer of the myocardium. Note the cardiomyocytes arranged circumferentially in the compact layer. (H) Cardiomyocytes arranged longitudinally and circumferentially in the spongy layer. *, lacunae; cf, circular fibers; cl, compact layer; lf, longitudinal fibers; lu, ventricular lumen; se, subepicardium; sl, spongy layer; ts, trabecular sheets. Stains: (A,B) Masson's trichrome; (C–H) Toluidine blue. Scale bars: (A) 100 μm; (B) 20 μm; (C) 200 μm; (D) 500 μm; (E) 2 mm; (F) 20 μm; (G) 20 μm; (H) 20 μm.