Question

1. the layer of the heart wall primarily responsible for the hearts pumping action is the: a. myocardium b. endocardium c. epicardium d. pericardium

Explanation:

The myocardium is the muscular middle layer of the heart wall. It contracts rhythmically to pump blood throughout the body. The endocardium is the inner - lining, the epicardium is the outer protective layer, and the pericardium is the sac that surrounds the heart.

Answer:

A. Myocardium