Parietal layer

The parietal layer of the serous pericardium is the inner portion of the parietal pericardium, consisting of a single layer of mesothelial cells that lines the internal surface of the outer fibrous pericardium. This layer is part of the double-layered serous pericardium, with the parietal layer lining the fibrous pericardium and the visceral layer (epicardium) covering the heart itself.

The parietal layer of the serous pericardium forms one boundary of the pericardial cavity, which contains a small amount of serous fluid to reduce friction during cardiac motion