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': 'True about tracheal bifurcation - \nSelect and explain. \nA. At lower border of T4, B. At lower border of T4 Tracheal ring has hoop-shaped process, C. Called Carina, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Trachea\n\nThe trachea is 10-15 cm long tube formed by C-Shaped hyaline cartilaginous rings and fibromuscular membrane.\nIt extends from the lower border of cricoid cartilage (at C6 level) to lower border of T4 or upper border of T5 vertebra (T4-T5 disc space) where it bifurcates.\nIts external diameter is about 2 cm in males and about 1.5 cm in females.\nIt has 16-20 cartilaginous rings.\n\nThe first tracheal ring is the broadest. The last ring at tracheal bifurcation shows carina, a triangular hoop-shaped process separating the bronchi, i.e.\nCarina is a bifurcation of the trachea.\n\nThe trachea is lined by ciliated columnar epithelium.\n\xa0It is supplied by the inferior thyroid artery and is drained by left brachiocephalic vein.\n\xa0Sensory and motor supply to the trachea is provided by the parasympathetic system through vagi and recurrent laryngeal nerve.\n\nVasomotor supply is by sympathetic fibres through middle cervical ganglion along inferior thyroid arteries.', 'role': 'assistant'}]