What contains pericardial sac?

The pericardial sac contains the pericardial fluid, which serves to lubricate the heart and reduce friction during its contractions. This double-walled structure encases the heart, providing protection and stability while allowing for the necessary movement of the heart as it beats. The outer layer, called the fibrous pericardium, is tough and helps anchor the heart in place, while the inner layer, or serous pericardium, produces the fluid that fills the sac.