What is the fibrous sac that surrounds the heart called?

The fibrous sac that surrounds the heart is known as the pericardium. This structure serves a crucial protective role by enclosing the heart and anchoring it within the chest cavity. The pericardium has two layers: the outer fibrous layer that provides protection and the inner serous layer that secretes fluid, allowing for smooth movement of the heart as it beats. This fluid-filled space between the layers helps reduce friction between the heart and surrounding structures. Understanding the function and structure of the pericardium is essential for recognizing its importance in cardiovascular health.