Final answer:
The atria are the thinner chambers of the heart referred to as the receiving chambers. They receive blood before it is pumped out by the ventricles.
Step-by-step explanation:
The atria are thinner chambers of the heart, which are sometimes called the receiving chambers of the heart. They receive blood coming into the heart before it is pumped out by the ventricles. The right atrium receives blood from the upper and lower body, while the left atrium receives blood from the lungs.