Pericardium (or epicardium)
The heart is a muscular organ that contracts rhythmically pumping the blood through the . Its walls consist of of three tunics or layers : the internal or endocardium , the middle or myocardium and the external or pericardium .
The endocardium is homologous with the intima of the blood vessels. It consists of a single layer of squamous endothelial cells resting on a thin subendothelial layer of loose connective tissue.
The myocardium is the thickest of the three tunics. It consists of cardiac muscle tissue.
The pericardium is a serous membrane in which the heart lies. The visceral layer of the pericardium corresponds to epicardium, which covers the heart externally.