DEVELOPMENT OF THE VASCULAR SYSTEM 



521 



renal veins join the cardinals, and at the same level a cross communication is 

 established on either side between the cardinal and subcardinal (Fig. 478). The 

 portion of the right subcardinal behind this cross communication disappears, while 



Left innominate 



Right innominate 

 Superior vena cava 



Prerenal part of 

 inferior vena cava 



Postrenal part of 

 inferior vena cava 



Internal jugular 

 External jugular 



Duct of Cuvier 



Left cardinal 



Left suprarenal 

 Left renal 



Left common iliac 

 External iliac 

 HypogaStric 

 FIG. 479. Diagram showing development of main cross branches between jugulars and between cardinals. 



that in front, i.e., the prerenal part, forms a connection with the ductus venosus 

 at the point of opening of the hepatic veins, and, rapidly enlarging, receives the 



Left innominate 



Right innominate. 



Superior vena cava 

 Azygos vein 



Prerenal part of 

 inferior vena cava 



Internal jugular 

 External jugular 

 Siibclavian 

 Highest left intercostal 



-Ligament of left vena cava 



Oblique vein of left atrium 

 Coronary sinus 

 Accessory hemiazygos vein 



Hemiazygos vein 

 Left suprarenal 

 Left renal 

 Left internal spermatic 



Left common iliac , 



External iliac 

 Hypogastric 

 FIG. 480. Diagram showing completion of development of the parietal veins. 



blood from the postrenal part of the right cardinal through the cross communica- 

 tion referred to. In this manner a single trunk, the inferior vena cava (Fig. 480), is 

 formed, and consists of the proximal part of the ductus venosus, the prerenal part 





