3C 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



aortic stems. From these stems five arteries (aortic arches) pass 

 upwards, one in each visceral arch, to terminate in the right and 

 left dorsal aortae, which run backwards to join together and form 



Ungual from 2nd 



uperior thyroid 



(from 3rd) 



ventral aorta 

 (right trunk) 



uentral aorta 

 (left trunk) 



left subclau. 

 th arch, left 

 th arch, left 



left dorsal aorta 



Fig. 28. — Showing what become of the Aortic Arches in the adult. Only the shaded 

 parts persist. 



one vessel at the 4th dorsal vertebra — the descending thoracic 

 aorta. 



As may be seen from figure 28, the first and second arches 

 disappear ; the third remains as the first part of the internal 

 carotid, the fourth forms the 1st and 2nd stages of the right 

 subclavian. On the left side the 4th aortic arch forms that 

 part of the arch of the aorta between the origin of the left carotid 



