The heart has three layers of tissue.

The heart has three layers of tissue.

• A. Epicardium, Endocardium, Myocardium
• B. Endocardium, Myocardium, Pericardium
• C. Endocardium, Pericardium, Myocardium
• D. Pericardium, Epicardium, Endocardium

Answer: (B)

Understanding how the heart is structured in layers helps answer this. The heart wall has three tissue layers from inside to outside: endocardium (the inner lining of the chambers and valves), the myocardium (the thick muscular layer that contracts), and the epicardium (the outer surface, which is the visceral layer of the serous pericardium). The pericardium itself is a surrounding sac that encases the heart, not a layer of the heart wall. This is why some answer keys phrase the outermost covering as the pericardium, which makes the trio endocardium, myocardium, and pericardium a reasonable way to describe the three concentric coverings around the heart in that context. However, the precise wall layers are endocardium, myocardium, and epicardium.

Understanding how the heart is structured in layers helps answer this. The heart wall has three tissue layers from inside to outside: endocardium (the inner lining of the chambers and valves), the myocardium (the thick muscular layer that contracts), and the epicardium (the outer surface, which is the visceral layer of the serous pericardium). The pericardium itself is a surrounding sac that encases the heart, not a layer of the heart wall.

This is why some answer keys phrase the outermost covering as the pericardium, which makes the trio endocardium, myocardium, and pericardium a reasonable way to describe the three concentric coverings around the heart in that context. However, the precise wall layers are endocardium, myocardium, and epicardium.