Visceral layer [Epicardium]

The visceral layer of the serous pericardium is the thin, inner serous membrane that is directly adherent to the surface of the heart. It is also known as the epicardium. This layer consists of a single layer of mesothelial cells and a thin underlying layer of connective tissue, and it covers the entire external surface of the heart, including the roots of the great vessels, before reflecting back to become the parietal layer of the serous pericardium. The visceral layer is separated from the parietal layer by the pericardial cavity, which contains a small amount of serous fluid to reduce friction during cardiac motion.