What is the membrane that encloses the heart called?

The membrane that encloses the heart is known as the pericardial sac. This fibrous and serous membrane surrounds the heart, providing it with protection and a lubricated environment that minimizes friction between the heart and surrounding structures as the heart beats. The pericardial sac consists of two layers: the outer fibrous pericardium, which provides structural support, and the inner serous pericardium that allows smooth movement with minimal friction.

The epicardium is the outermost layer of the heart wall, which is part of the heart's anatomy but does not serve the same encapsulating function as the pericardial sac. The myocardium refers to the muscular middle layer of the heart's wall responsible for the heart's contractions, and the endocardium is the innermost layer lining the chambers of the heart and covering the heart valves. While all these components are essential for the heart's structure and function, the pericardial sac is specifically the enclosing membrane for the heart.