AAMI Anatomy 1 Practice Exam

The heart is enclosed by a protective sac called the pericardium, and the space inside that sac between its serous layers is the pericardial cavity. This cavity normally contains a small amount of lubricating fluid (pericardial fluid) that lets the heart glide smoothly as it beats, reducing friction. The other options don’t fit this description: the abdominal cavity houses digestive organs; the pleural cavities surround the lungs and contain pleural fluid; the mediastinum is the central thoracic compartment that contains the heart but is not the specific fluid-filled space around it. So, the cavity surrounding the heart with a small amount of fluid is the pericardial cavity.