Corpus: Epicardium

The epicardium forms the outermost layer of the heart. It is identical to the visceral leaf (lamina visceralis) of the pericardium.

The epicardium is firmly fused to the myocardium. It consists of tunica serosa and tela subserosa.

The tunica serosa is divided into a single-layered squamous epithelium (mesothelium) and a thin lamina propria, which in turn consists of the basement membrane and underlying loose connective tissue with elastic fibres. The tela subserosa contains the epicardial fatty tissue.

The epicardium is most pronounced over the atria. At the aortic root and in the sulcus coronarius it is raised in folds.

The epicardial fatty tissue compensates for incongruities on the surface of the heart and is most strongly developed in the coronary sulcus and in the anterior interventricular sulcus. The larger coronary vessels are embedded in it.

The epicardium produces a small amount of fluid, the pericardial fluid, which moistens the gap between the epicardium and the outer parietal leaflet of the pericardium, thereby reducing the friction between the two leaflets.