AORTA 143 



and parietal and each set is again divided into paired and un- 

 paired groups, which supply the viscera, the muscles of the 

 trunk and the lower limbs. 



The lumbar arteries which supply the muscles of the trunk 

 arise down the sides of the aorta opposite the bodies of the 

 lumbar vertebras. 



The Common Carotid arteries vary slightly at their com- 

 mencement ; otherwise they are similar in course and dis- 

 tribution. 



The Bight Common Carotid artery arises from the innomi- 

 nate artery behind the right sterno-clavicular articulation; the 

 left arises direct from the arch of the aorta about an inch below 

 the left sterno-clavicular articulation. They both terminate at the 

 level of the upper border of the thyroid cartilage of the larynx,, 

 or the lower border of the third cervical vertebra. They are 

 separated from one another below by the trachea and oeso- 

 phagus, above by the pharynx. 



The common carotid artery is enclosed in a fibrous sheath 

 with the vagus nerve and internal jugular vein. It lies on 

 scalenus anticus and longus colli muscles below, and rectus 

 capitis anticus major above, and is covered by sterno-mastoid. 

 On its outer side lies the internal jugular vein, which slightly 

 overlaps it below. 



Branches. The artery bifurcates at its termination, forming 

 the external and internal carotid arteries. 



The External Carotid artery extends from the bifurcation of 

 the common carotid artery to the back of the neck of the man- 

 dible, where it terminates by dividing into the superficial tem- 

 poral and internal maxillary arteries. 



Branches. Occipital. 



Superficial temporal. 



Internal maxillary, and five other branches which 

 supply the face, tongue, pharynx, and larynx. 



The Occipital artery runs upwards under the mastoid process 

 to the back of the scalp, and terminates near the inner end of 

 the superior curved line of the occipital bone. By dividing into- 

 branches it supplies the scalp and surrounding structures. 



The Superficial Temporal artery commences in the parotid 



