CAROTID ARTERIES 145 



The Internal Maxillary artery commences in the parotid gland 

 and passes inwards to supply the teeth and structures behind 

 the superior maxilla and mandible. 



The Internal Carotid artery commences at the bifurcation of 

 the common carotid and terminates in the brain by dividing into 

 branches. At first it lies on the outer side of the external 

 carotid, but passes behind it and gets to the inner side. It 

 passes up at the back of the parotid gland and reaches the brain 

 by means of the carotid canal in the temporal bone. 



The Subclavian arteries also vary slightly at their com- 

 mencement, the right subclavian artery commencing at the 

 bifurcation of the innominate artery behind the right sterno" 

 clavicular articulation, and the left subclavian artery commencing 

 from the arch of the aorta behind the lower part of the manu- 

 brium sterni. The artery arches up over the apex of the lung, 

 and passing between scalenus anticus and medius, it ends at the 

 lower border of the first rib by becoming the axillary artery. 

 The scalenus anticus, in crossing the subclavian artery divides it 

 into three parts the first part being internal to the muscle, the 

 second behind it, and the third on the external side. The 

 third part of the artery is separated from scalenus medius by 

 the cords of the brachial plexus. 



Branches. From the first part : 



Vertebral, thyroid axis, internal mammary. 

 From the second part : Superior intercostal. 



The Vertebral artery arises from the subclavian artery just 

 between scalenus anticus and longus colli. It passes backwards 

 ;and upwards through the foramina in the transverse processes 

 of the cervical vertebrae, and entering the foramen magnum, ter- 

 minates by uniting with its fellow of the opposite side to form 

 the basilar artery. The basilar artery divides again, and the 

 branches are united by the posterior communicating arteries to 

 the internal carotid arteries to form the Circle of Willis for the 

 free supply of the brain. 



The Thyroid Axis is a very short trunk, which ends by 

 dividing into three the inferior thyroid, transverse cervical, 

 and suprascapular which supply the shoulder and adjacent 

 parts. 



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