In which space within the mediastinum does the heart sit, separated from other mediastinal structures by the pericardium?

1. The heart is located within the thoracic cavity, medially between the lungs, in the mediastinum. 2. A tough membrane called the pericardium separates the heart from other mediastinal structures. 3. The heart sits in its own space within this membrane, called the pericardial cavity. 4. The pleural cavity surrounds the lungs and the peritoneal cavity surrounds abdominal organs, and "mediastinal sinus" is not the name used for this space so none of these three name the heart's own cavity. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 19 "The Cardiovascular System: The Heart", section 19.1, p. 824_