Referring to the pericardium, the sac of fibrous tissue that surrounds the heart. The inner surface of the pericardium is lined by a layer of flat cells (mesothelial cells). The pericardial sac normally contains a small amount of fluid which acts as a lubricant to allow normal heart movement within the chest. A pericardial effusion refers to the presence of too much pericardial fluid, a serous fluid of a pale yellow color, within the pericardium.

Pertaining to the pericardium, the fibrous sac that surrounds the heart