This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
[{'content': 'All the structures lie behind thoracic duct at the root of the neck except \nSelect and explain. \nA. Veebral aery and vein, B. Medial border of the scalenus anterior, C. Right phrenic nerve, D. Thyrocervical trunk and its branches', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The thoracic duct begins as a continuation of the upper end of the cisterna chyli near the lower border of the twelfth thoracic veebra and enters the thorax through the aoic opening of the diaphragm.In the NeckThe thoracic duct forms an arch rising about 3-4 cm above the clavicle. The arch has the following relations:Anteriorly: (i) Left common carotid aery, (ii) left vagus, and (iii) left internal jugular vein.Posteriorly: (i) Veebral aery and vein, (ii) sympathetic trunk, (iii) thyrocervical trunk and its branches, (iv) left phrenic nerve, (v) medial border of the scalenus anterior, (vi) preveebral fascia covering all the structures mentioned, and (vii) the first pa of the left subclan aery.Ref: BD Chaurasia; Volume 1; 6th edition; Page no: 272', 'role': 'assistant'}]