Pericardium is the double membrane sac that lines the outside of the heart.

Pericardium is the double membrane sac that lines the outside of the heart.

• A. Thick muscular middle layer
• B. Double membrane sac that lines the outside of the heart
• C. Smooth inner lining
• D. The heart's pumping chambers

Answer: (B)

The main idea is knowing what the pericardium is and where it sits. The pericardium is a double-layered sac that surrounds the heart, with an outer fibrous layer and an inner serous layer. The serous layer includes a parietal portion lining the fibrous sac and a visceral portion that adheres to the heart surface, so it effectively lines the outside of the heart. This is why the description fits: a double membrane sac around the heart. The other terms refer to different heart structures—the thick muscular middle layer is the myocardium, the smooth inner lining is the endocardium, and the heart’s pumping chambers are the atria and ventricles.

The main idea is knowing what the pericardium is and where it sits. The pericardium is a double-layered sac that surrounds the heart, with an outer fibrous layer and an inner serous layer. The serous layer includes a parietal portion lining the fibrous sac and a visceral portion that adheres to the heart surface, so it effectively lines the outside of the heart. This is why the description fits: a double membrane sac around the heart. The other terms refer to different heart structures—the thick muscular middle layer is the myocardium, the smooth inner lining is the endocardium, and the heart’s pumping chambers are the atria and ventricles.