Final answer:
The left and right atria receive blood from veins, with the right atrium receiving deoxygenated blood from the body while the left atrium receives oxygenated blood from the lungs.
Step-by-step explanation:
The left and right atria both receive blood from veins. The right atrium receives oxygen-poor blood from the body through the superior vena cava and inferior vena cava. In contrast, the left atrium receives oxygen-rich blood from the lungs through the pulmonary veins. The atria are considered the receiving chambers of the heart, as they collect incoming blood before it moves into the ventricles.
Each atrium then pumps the blood into its corresponding ventricle below it. The right ventricle sends the deoxygenated blood to the lungs for oxygenation, whereas the left ventricle pumps the oxygenated blood to the rest of the body through the aorta. This double circulation system ensures that oxygenated and deoxygenated blood are efficiently separated and directed to their appropriate destinations within the body.