THE CIRCULAl'ORY OR VASCULAR SYSTEM 99 



of the heart with nutrition. These arteries encircle the 

 heart in both the horizontal and the vertical directions. 



The innominate artery is the first and largest 

 trunk given off from the arch of the aorta; it is about i^ 

 inches in length, and ascends obliquely toward the right 

 sternoclavicular articulation, where it divides into the 

 right common carotid and right subclavian arteries. It 

 occasionally gives off a small branch to the thyroid gland. 



The Common Carotid Arteries. The right arises 

 from the bifurcation of the innominate artery, opposite 

 the right sternoclavicular articulation. The left ascends 

 from the arch of the aorta. The right is shorter than the 

 left, more anterior, and somewhat larger. 



The right common carotid ascends the neck perpendicu- 

 larly by the side of the trachea and larynx, from behind the 

 right sternoclavicular articulation to the level of the upper 

 border of the thyroid cartilage, where it divides into the 

 right external and internal carotids. 



The left common carotid ascends from the aortic arch 

 obliquely outward to the side of the neck, and upward by 

 the side of the trachea and esophagus to the upper border 

 of the thyroid cartilage, where it divides into the left 

 external and internal carotids. 



The external carotid ascends perpendicularly be- 

 tween the lower jaw and auditory meatus, where it divides 

 into two terminal branches, the temporal and the internal 

 maxillary ; it gives off the following branches : 



Anterior. Posterior. 



Superior thyroid. Occipital. 



Lingual. Posterior auricular. 

 Facial. 



Ascending. Terminal. 



Ascending pharyngeal. Superficial temporal. 

 . '/v * ' , Internal maxillary. , . i 



