<prompt> Septum secundum arises from:Bulbus cordisPrimitive ventriclePrimitive atriumSinus venosus  <response>: Septum secundum Grows down from theroof of the common atriumprimitive atriumtoward the atrioventricular endocardial cushions. Present on the right side of the septum primum. Contains foramen ovale for the pasage of blood from RA to LA. Note Order of hea tube on day 21 from caudal to cranial Sinus venosus Atrium Ventricle Bulbus cordis Truncus aeriosus 