Final answer:
The three layers of the heart from exterior to interior are the epicardium, myocardium, and endocardium, with the pericardium being a protective sac encompassing the heart, not a layer of the heart wall(option a).
Step-by-step explanation:
The layers of the heart from exterior to interior are correctly identified in option (a): Epicardium, myocardium, endocardium. The heart wall is composed of three main layers:
The epicardium: This is the outermost layer and also forms the innermost layer of the pericardium that surrounds the heart.
The myocardium: The middle and thickest layer, consisting mainly of cardiac muscle tissue, responsible for the heartbeat.
The endocardium: The innermost layer that lines the internal walls of the heart's chambers.
It is important to note that the pericardium is not one of the three heart wall layers but rather a protective sac encompassing the heart that includes the epicardium within it. The pericardium consists of two membranes with a fluid-filled cavity in between to reduce friction.
Hence, the answer is option a.