Question

which best describes the pericardium?
○ structures inside the heart that ensure that blood flows in one direction only
○ a sac around the heart that allows the heart muscle to receive oxygen
○ a sac around the heart that protects the heart and chest tissues
○ structures inside the heart that bring blood to the lungs for oxygenation

Explanation:

The pericardium is a double - walled sac that surrounds the heart. Its main functions include protecting the heart and reducing friction between the heart and surrounding chest tissues. The first option describes heart valves, the second is inaccurate as the pericardium is not directly involved in oxygen - delivery to heart muscle, and the fourth describes structures related to the pulmonary circulation within the heart.

Answer:

a sac around the heart that protects the heart and chest tissues