This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CVS Embryology, Subject name: Anatomy
[{'content': 'Septum secundum arises from: \nSelect and explain. \nA. Bulbus cordis, B. Primitive ventricle, C. Primitive atrium, D. Sinus venosus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Septum secundum Grows down from theroof of the common atrium(primitive atrium)toward 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', 'role': 'assistant'}]