516 



ANGIOLOGY 





The Anterior Ventral Aortae. These persist on both sides. The right forms (a) 

 the innominate artery, (6) the right common and external carotid arteries. The 

 left gives rise to (a) the short portion of the aortic arch, which reaches from the 

 origin of the innominate artery to that of the left common carotid artery; (6) the 

 left common and external carotid arteries. 



The Aortic Arches. The first and second arches disappear early, but the dorsal 

 end of the second gives origin to the stapedial artery (Fig. 474), a vessel which 

 atrophies in man but persists in some mammals. It passes through the ring of the 

 stapes and divides into supraorbital, infraorbital, and mandibular branches which 

 follow the three divisions of the trigeminal nerve. The infraorbital and 



mari- 



Post. cerebral a. 



Ant. cerebral li. 



Supraorbital br. 

 of stapedial a. 



Trigeminal nerve 



Maxillary nerve 

 Infraorbital a. 



Mandibular nerve 



Mandibular a. 

 Ext. max. a. 



Lingual a, 

 Sup. thyroid a 



Stapedial a. 



Int. carotid a. 



Common carotid a. 



Aortic arch 

 Pulmonary arch 



Pulmonary art. 



Dorsal aorta 

 FIG. 474. Diagram showing the origins of the main branches of the carotid arteries. (Founded on Tandler.) 



dibular arise from a common stem, the terminal part of which anastomoses with 

 the external carotid. On the obliteration of the stapedial artery this anastomosis 

 enlarges and forms the internal maxillary artery, and the branches of the stapedial 

 artery are now branches of this vessel. The common stem of the infraorbital and 

 mandibular branches passes between the two roots of the auriculotemporal nerve 

 and becomes the middle meningeal artery ; the original supraorbital branch of the 

 stapedial is represented by the orbital twigs of the middle meningeal. The third 

 aortic arch constitutes the commencement of the internal carotid artery, and is 

 therefore named the carotid arch. The fourth right arch forms the right sub- 

 clavian as far as the origin of its internal mammary branch ; while the fourth left 

 arch constitutes the arch of the aorta between the origin of the left carotid artery 



