The right atrium is one of four chambers (two atria and two ventricles) in the human heart. It receives de-oxygenated blood from the superior and inferior vena cavae and the coronary sinus, and pumps it into the right ventricle through the tricuspid valve.
Attached to the right atrium is the right auricular appendix.
right heart: (vena cavae, coronary sinus) → right atrium (fossa ovalis) → tricuspid valve → right ventricle → pulmonic valve → (pulmonary artery and pulmonary circulation)
left heart: (pulmonary veins) → left atrium → mitral valve → left ventricle → aortic valve → (aorta, aortic sinus and systemic circulation)
pericardium | epicardium | endocardium | myocardium
conduction system: cardiac pacemaker | Purkinje fibers | bundle of His | SA node | AV node