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': 'In a patient with a tumor in superior mediastinum compressing the superior vena cava, all of the following veins would serve as alternate pathways for the blood to return to the right atrium, except- \nSelect and explain. \nA. Lateral thoracic vein, B. Internal thoracic vein, C. Hemiazygos vein, D. Vertebral venous plexus', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Whenever there is an obstruction in superior or inferior vena cava, collateral circulation opens up to connect inferior vena cava and superior vena cava. This helps in circulation being maintained by draining into the right atrium. The veins that can form collaterals include\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Superior epigastric\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Internal thoracic\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Lateral thoracic\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Thoracoepigastric\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Posterior intercostal\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Lumbovertebral\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Superficial epigastric\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Superficial circumflex iliac\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Deep circumflex iliac\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Inferior epigastric\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 External pudendal\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Azygous\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Hemiazygous\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Ascending lumbar', 'role': 'assistant'}]