In the following description of the heart wall structure, the WRONG option is A: The heart wall consists of endocardium, myocardium and epicardium. B: The surface of endocardium is covered by endothelium. C: Purkinje fibers are distributed in the subendocardial layer of the ventricle (心室). D: Myocardium consists mainly of smooth muscle fibers. E: Epicardium is serosa.