function of right atrium and left atrium of human heart

aorta arteries arterioles artery atria atrioventricular atrium blood capillaries chamber chambers cycle deoxygenated electrical endocardium epicardium function heart human impulse low lower lungs myocardium node oneway organ oxygenated oxygenrich performs pressure pulmonary pump pumps receives right signal signals situated tissue tricuspid upper valve veins ventricle ventricles venules