parietal serous layer

The parietal serous layer, also known as the parietal pericardium, is a smooth, moisture-exuding membrane that lines the fibrous pericardium, the outer sac enclosing the heart. This layer is part of the serous membrane system, which secretes serous fluid.12

The parietal serous layer bends back to cover the heart, forming the visceral serous layer (or epicardium). Between these two serous layers is the pericardial cavity, which normally contains a small amount of pericardial fluid (10-15 ml) secreted by the membranes. This fluid acts as a lubricant, allowing the two membranes to glide smoothly over each other with each heartbeat.1