Ventricles

Internally, the heart is divided into four hollow chambers, two on the left and two on the right. The lower chambers, the "ventricles," force blood out of the heart into the arteries to be carried back to the various sites throughout the body. The right ventricle has a much thinner wall than the left ventricle. This chamber pumps blood a fairly short distance to the lungs. The left ventricle, however, must force blood to all other parts of the body against a great flow of resistance, so the walls are stronger.