xv, 6 Canizares: Abnormalities of Vertebral Artery 455 



External carotid 



'Internal carotid 



.Common carotid 

 -Vertebral artery 



Ventral aorta 



Right pulmonary' 

 artery 



A&rtic arch 



-•Ductus arteriosus 



Subclavian artery 

 Left pulmonary arteiy 



Trunk of pulmonary arterjj 

 Dorsal aorta 



Fig. 1. Diagram, showing the aortic arches and their derivatives in human embryo* witk 

 normal origin of vertebral arteries (modified after Prentiss). 



on the left side, and the innominate and the proximal portion 

 of the subclavian upon the right. » 



Prentiss (6) says: 



The ventral longitudinal anastomosis of the dorsal rami of the first 

 seven pairs of dorsal intersegmental arteries, gives rise to the vertebral 



First pair of inter- 

 segmental arteries \~ ^ 



Vertebral 

 arteries 



i 



Seventh pair of 

 intersegmental arterict 

 I 



Bulbus *cordu 



Sinvx veno*** 

 Atrium 



Ventricle 

 1st 2d 3d Uth 6th 

 Cephalic aortic arches 



FIG. 2. Diagram, showing stage of five aortic arches and origin of the rtrtebral arteries 

 (modified after Cunningham). 



