<Tr> <Th> TA </Th> <Td> A12. 1.08. 001 </Td> </Tr> <Tr> <Th> FMA </Th> <Td> 9869 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The pericardium (from the Greek περί, "around" and κάρδιον, "heart") 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>

The inner most layer of the heart is