Which layer of the pericardium directly covers the heart?

The visceral pericardium is the layer that directly covers the heart. It is a thin, serous membrane that tightly adheres to the surface of the heart and forms part of the heart's protective covering. This layer not only protects the heart but also allows for smooth movement as the heart contracts and relaxes, thanks to the serous fluid found between the visceral and parietal layers of the pericardium.

The parietal pericardium, while part of the pericardial sac, does not touch the heart directly; instead, it forms the outer layer of the pericardium that surrounds the heart. The pericardial cavity is the space between the visceral and parietal layers that contains pericardial fluid, providing lubrication for heart movement, but it is not a layer of the pericardium itself. The term "serous membrane" describes a type of membrane that includes both the visceral and parietal pericardium, but it does not specifically identify the layer that covers the heart. Therefore, the visceral pericardium is the correct choice as it is specifically designed to envelop the heart directly.