The ventricles are the two lower cardiac chambers
that collect blood from the upper chambers (atria) and pump it out of the heart.
Because the ventricles
pump blood away from the heart, they have thicker walls than the atria
so that they can withstand the associated higher blood pressures.
The right ventricle pumps oxygen-poor blood through the pulmonary artery
and to the lungs. The left ventricle pumps oxygen-rich
blood through the aorta and to the rest of the body.