Final answer:
The upper chambers of the heart, the right atrium, and the left atrium, contract to push blood into the lower chambers, the right ventricle, and the left ventricle.
Step-by-step explanation:
The upper chambers of the heart, the right atrium, and the left atrium, act as receiving chambers and contract to push blood into the lower chambers, the right ventricle, and the left ventricle.
The upper chambers of the heart, the right atrium, and the left atrium, contract to push blood into the lower chambers, the right ventricle, and the left ventricle.