<Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The pericardium is a double - walled sac containing the heart and the roots of the great vessels . The pericardial sac has two layers, a serous layer and a fibrous layer . It encloses the pericardial cavity which contains pericardial fluid . </P> <P> The pericardium fixes the heart to the mediastinum, gives protection against infection, and provides the lubrication for the heart . It receives its name from Ancient Greek peri (περί; "around") and cardion (κάρδιον; "heart"). </P> <P> The pericardium is a tough double layered fibroserous sac which covers the heart . The space between the two layers of serous pericardium (see below), the pericardial cavity, is filled with serous fluid which protects the heart from any kind of external jerk or shock . There are two layers to the pericardial sac: the outermost fibrous pericardium and the inner serous pericardium . </P>

The tough covering that anchors and protects the heart