This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of the female genital tract, Subject name: Gynaecology & Obstetrics
[{'content': 'Anatomical sphincter of fallopian tubes : \nSelect and explain. \nA. Infundibulum, B. Isthmus, C. Intramural, D. Ampulla', 'role': 'user'}, {'content': "Answer: C \nExplanation: The intramural pa is the innermost pa of the fallopian tube which traverses the myometrium to open into endometrial cavity. It is the shoest pa length being 18 mm and narrowest pa with internal diameter being 1mm or less so that only finest cannula can be passed through it during salpingostomy operation. Ref: Shaw's Textbook of Gynaecology, 15th edition, page no: 11", 'role': 'assistant'}]