Final answer:
The heart is composed of three layers: the epicardium, the myocardium, and the endocardium.
Step-by-step explanation:
The heart is composed of three layers: the epicardium, the myocardium, and the endocardium. The epicardium is the outermost layer of the wall of the heart and is also the innermost layer of the pericardium. The myocardium is the middle layer and consists of the heart muscle cells. The endocardium is the inner lining of the heart.