What is the name of the cavity surrounding the heart?

The name of the cavity surrounding the heart is the pericardium. This is a double-walled sac that contains the heart and the roots of the great vessels. The pericardium serves several important functions, including providing a protective layer, anchoring the heart to surrounding structures, and assisting with the regulation of the heart's movements as it beats.

In contrast, the thoracic cavity encompasses a larger area that includes the lungs and heart along with other structures, while the mediastinum is a specific central compartment within the thoracic cavity that contains the heart, trachea, esophagus, and other vital structures. The peritoneum, on the other hand, is a membrane that lines the abdominal cavity and covers the abdominal organs, making it unrelated to the heart. Thus, the pericardium is the specific cavity that directly encompasses and protects the heart.