<prompt> Which of the following is true about the staing course of azygous veinLateral to superior vena cavaPosterior to inferior vena cavaAnterior to lumbar veinAnterior to inferior vena cava  <response>: AZYGOS VEIN The azygos vein drains the thoracic wall and the upper lumbar region.It forms an impoant channel connecting the superior and inferior venaecavae.The term azygos means unpaired.The vein occupies the upper pa of the posterior abdominal wall and the posterior mediastinum.It is formed by the union of the lumbar azygos,right subcostal and right ascending lumbar veins. Course 1.It enters the thorax by passing through the aoic opening of the diaphragm. 2.It then ascends up to fouh thoracic veebra where it arches forwards over the root of the right lung and ends by joining the posterior aspect of the superior venacava just before the latter pierces the pericardium. REF.BD CHAURASIAS HUMAN ANATOMY.VOL.1,FIFTH EDITION.PAGE NO.218 