THE THORAX AND ITS CONTENTS 



lOI 



The supreme intercostal veins emerge craniad to the 

 second rib and empty into the precavae near the heart; the 

 right emptying craniad to, or with, the azygos vein. 



The azygos vein, as its name indicates, is not paired and 

 drains the parietal and dorsal regions of the thorax. It lies 

 along the right dorsolateral side of the thoracic aorta and 

 empties into the right superior vena cava before it enters the 

 right atrium. Method: This vein is readily seen through an 



sic,^ 



Fig. 27. — Principal veins of the precaval system, dorsal view. Coronaries 

 are not shown. A, azygos; AT, anterior thoracic; EJ, external jugular; IJ, 

 internal jugular; IM, internal mammary (sternal); LPC, left precava; LS, left 

 subclavian; PA, posterior auricular; PC, postcava; PF, posterior facial; RPC, 

 right precava; RS, right subclavian; SIC, supreme intercostal; SV, sinus venosus; 

 TJ, transverse jugular. 



opening made caudad to the heart by pressing the esophagus 

 ventrad and the aorta to the left side. Its confluence with 

 the right precava is readily seen by pushing the heart to the 

 left. It is often closely associated, sometimes confluent with, 

 the supreme intercostal vein. 



Vena cava inferior (postcava): The postcava is a single 

 vessel which extending craniad from the confluence of the 

 common iliac veins passes through the diaphragm about 2 

 cm. ventrolaterad to the point where the esophagus passes 

 through it and empties into the sinus of the right atrium of the 

 heart. It receives no important veins in the thoracic region. 



