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: ENT
[{'content': 'Which of the following causes opening of Eustachian tube? \nSelect and explain. \nA. Salpingopharyngeus, B. Levator veli palatini, C. Tensor veli palatini, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The Eustachian tube/auditory tube in the adult is 36 mm in length. (Range 32-38 mm) From its tympanic end, it runs downward\xa0forward and medially joining an angle of 45° with horizontal.\xa0\nIn infants, the tube is shorter, wider and is more horizontal.\nIt has two parts—a pharyngeal cartilaginous part which forms 2/3rd (24 mm) of its length (i.e. inner or medial part) and a\xa0tympanic bony part which forms remaining 1/3rd (outer or lateral part) (12 mm). This is just reverse of external auditory canal\nThe two parts meet at isthmus which is the narrowest part of tube.\nThe fibers of origin of tensor palati muscles are attached to lateral wall of the tube. Contraction of this muscle during\xa0swallowing, yawning and sneezing opens the tube and this helps in maintaining equality of air pressure on\xa0both sides\xa0of tympanic membrane. Contraction of levator palati muscles which runs below the floor of cartilaginous part also helps in\xa0opening the tube.\nIt is lined by pseudostratified columnar ciliated epithelium (cartilaginous part contains numerous mucous glands).\n\nRef. Dhingra 6/e, p 57, 5/e, p 63', 'role': 'assistant'}]