Emergency Medical Technician (EMT) Intermediate Practice Exam

What anatomical structure prevents cardiac overdistention and anchors the heart within the thoracic cavity?

1. Epicardium

2. Pericardium

3. Myocardium

4. Endocardium

The correct answer is: Pericardium

The pericardium is the anatomical structure that serves to prevent cardiac overdistention and anchors the heart within the thoracic cavity. It is a double-walled sac that surrounds the heart, providing both a protective layer and a barrier that limits excessive movement and overfilling of the heart chambers. The outer layer, known as the fibrous pericardium, anchors the heart to surrounding structures such as the diaphragm and great vessels, which helps maintain its position in the mediastinum. The inner layer, or serous pericardium, contains a small amount of lubricating fluid that reduces friction as the heart beats. This setup is crucial for maintaining proper heart function and ensuring that the heart operates effectively without being subject to undue stress from surrounding structures or pathological conditions. While other layers of the heart play significant roles in its function and structure, such as the myocardium in muscle contraction or the endocardium lining the heart chambers, it is the pericardium that primarily addresses issues of protection, support, and limiting overdistention.