Answer
8. ANS a. Both atria contract together, and both right and left ventricles contract in unison.
Work Step by Step
Blood in the left atrium is oxygenated blood coming from the lungs; blood in the right atrium is deoxygenated blood coming form tissues by way of superior and inferior vena cavae. The right ventricle pumps blood to the lungs to be oxygenated; the left ventricle -- the most powerful chamber of the heart-- pumps oxygenated blood from the heart to all tissues by way of the aorta, the aortic arch and the ascending and the descending branches of the aorta.
