This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
[{'content': 'Patent foramen ovale is due to \nSelect and explain. \nA. Failure of closure of sinoatrial orifice, B. Failure of fusion of septum primum and endocardial cushion, C. Failure of fusion of septum primum and septum intermedium, D. Failure of fusion of septum primum and septum secondum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The primitive atrium is divided into left and right atria by an interatrial septum which is formed by fusion of septum primum and septum secundum. The sequence of events are as follows\n\nSeptum primum arises from the roof of the common atrium (primitive atrium) and grows caudally towards septum intermedium (fused AV cushions).\nForamen primum is formed between the free border of growing septum primum and fused AV cushions (septum intermedium).\nShortly afterwards the septum primum fuses with septum intermedium (fused AV cushions), obliterating foramen primum\nForamen secundum is formed by degeneration of cranial part of septum primum.\nSeptum secundum grows caudally to the right of septum primum and overlaps the foramen secundum. The passage between septum primum and septum secundum is called foramen ovale. After birth, foramen ovale closes by fusion of septum primum with septum secundum. Failure of fusion of these two septa results in patent foramen ovale.', 'role': 'assistant'}]