What term describes the tough membrane that encloses and protects the heart?

The term that describes the tough membrane enclosing and protecting the heart is the pericardium. This structure is a double-walled sac that surrounds the heart, providing both a protective barrier and preventing it from overexpanding. The outer layer consists of a fibrous pericardium that is thick and durable, while the inner layer, known as the serous pericardium, has two sub-layers that allow for smooth movement of the heart as it beats.

The myocardium refers to the muscular layer of the heart responsible for pumping blood, while the endocardium is the inner lining of the heart chambers and valves. The epicardium is the outer layer of the heart wall itself, which lies directly on top of the myocardium. Each of these terms describes different components or layers of the heart, but only the pericardium serves as the protective membrane encasing the heart.