SUPERIOR AND INFERIOR VEN/E CAV^E. 315 



branches. 3. The azygos veins. 4. The vertebral and spinal veins. 5. 

 The cardiac veins. 6. The portal vein. 7. The pulmonary veins. 



SUPERIOR VENA CAVA, WITH ITS FORMATIVE 

 BRANCHES. 



Vence Innominatce. 



The Vena Innominatce are two large trunks, formed by the union of 

 the internal jugular and subclavian vein, at each side of the root of the 

 neck. 



The Right vena innominata, about an inch and a quarter in length, lies 

 superficially and externally to the arteria innominata, and descends almost 

 vertically to unite with its fellow of the opposite side in the formation of 

 the superior cava. At the junction of the jugular and subclavian veins it 

 receives from behind the ductus lymphaticus dexter, and lower down it 

 has opening into it the right vertebral, right internal mammary, and right 

 inferior thyroid vein. 



The Left vena innominata, considerably longer than the right, extends 

 almost horizontally across the roots of the three great arteries arising from 

 the arch of the aorta, to the right side of the mediastinum, where it unites 

 with the right vena innominata, to constitute the superior cava. 



It is in relation in front with the left sterno-clavicular articulation and 

 the first piece of the sternum. At its commencement it receives the tho- 

 racic duct which opens into it from behind, and in its course is joined by 

 the left vertebral, left infenor thyroid, left mammary, and by the superior 

 intercostal vein. It also receives some small veins from the mediastinum 

 and thymus gland. There are no valves in the vense innominatae. 



SUPERIOR VENA CAVA. 



The superior cava is a short trunk about three inches in length, formed 

 by the junction of the two vense innominata). It descends perpendicularly 

 on the right side of the mediastinum, and entering the pericardium termi- 

 nates in the upper part of the right auricle. 



It is in relation in front with the thoracic fascia, which separates it from 

 the thymus gland, and with the pericardium ; behind with the right pulmo- 

 nary artery, and right superior pulmonary vein ; internally with the ascend- 

 ing aorta ; externally with the right phrenic nerve, and right lung. Im- 

 mediately before entering the pericardium it receives the vena azygos 

 major. 



INFERIOR VENA CAVA, WITH ITS FORMATIVE 

 BRANCHES. 



Eiac Veins. 



The External iliac vein lies to the inner side of the corresponding artery 

 at the os pubis ; but gradually gets behind it as it passes upwards along 

 the brim of the pelvis, and it terminates opposite the sacro-iliac symphysis 

 by uniting with the internal iliac, to form the common iliac, vein. Imme- 

 diately above Poupart's ligament it receives the epigastric and circumflexa 

 ilii veins ; it has no valves. 



