Pls. check the following:
Heart
Sinus venosus (R horn): smooth part of right atrium (sinus venarum) and the "valve" of the superior vena cava. The sino-atrial node.
Sinus venosus (L horn): coronary sinus, valve of coronary sinus
Valve of sinus venosus (R): border of smooth part of right atrium (crista terminalis)
Valve of sinus venosus (L): part of atrial septum

Common atrium: rough part of right and left atria and the auricles

Embryonic pulmonary vein: large part of the left atrial wall

Septum primum: left side of the atrial septum

Septum secundum: right side of the atrial septum

Foramen secundum: dimple in the atrial septum seen from left side (fossa ovalis, ok)