Right atrium

The right atrium is one of four chambers (two atria and two ventricles) in the heart. It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins. This blood flows into the right ventricle through the tricuspid valve. 

The right atrium contains the sinoatrial (SA) node. Attached to the right atrium is the wrinkly right auricle.