A chamber of the heart that receives blood returning to the heart from the body or lungs. Vertebrates have two atria, one receiving oxygenated blood and the other deoxygenated blood.
Ventricle: one of two large chambers in the heart that pump blood out to the lungs or body
Pulmonary Vein: a vessel that carries oxygenated blood from the lungs to the left atrium
Vena Cava: a large vein carrying deoxygenated blood into the right atrium