1. The outer sac that encloses and envelops the heart is the:
O myocardium
O epicardium
O pericardium
O endocardium
2. Which of the following is the most powerful muscular layer of the heart wall?
O endocardium
O myocardium
O pericardium
O epicardium

1. Pericardium.

2. Myocardium.

Explanation:

Pericardium is the outer sac that surrond and envelope the heart. The pericardial sac envelope the pericardial cavity which contain the pericardial fluid. Pericardium fixes the heart to the mediastinum. It protects the heart against infection and lubricates the heart.

Myocardium is the thickest muscular layer of the heart and it is made up of cardiomyocytes. It is found in the walls of the four Chambers of the heart. It pumps blood to the tissues of the body.