Arteries are blood vessels that carry blood from the heart to various parts of the body. The aorta is the largest artery in the body, which receives oxygenated blood from the heart for circulation throughout the body. The pulmonary artery carries blood with carbon dioxide from the heart to the lungs.
Atria (Plural for atrium) are the two top chambers of the heart that receive blood from the body and transfer it to the ventricles that pumps it to required parts of the body. Oxygenated blood is received in the left atrium from the lungs and is transferred to left ventricle for circulation throughout the body, passing through aorta.
Blood with depleted oxygen and carrying carbon dioxide from the body, flow to the right atrium, through pulmonary veins, and is transferred to right ventricle for pumping to lungs.