110 A MANUAL OF ANATOMY. 



Second Portion. Superior intercostal. 

 Third Portion. Posterior scapular (more often than 

 from the transverse cervical). 



The Vertebral Artery. Figs. 10, 18, 20, 22. 



This is the first branch of the subclavian. It arises 

 from the upper and back part of the artery, near the inner 

 edge of the scalenus anticus, passes vertically upward to 

 enter the foramen in the transverse process of the sixth 

 cervical vertebra. 



The artery continues upward through all the foramina 

 in the vertebrae above. On reaching the atlas it winds 

 backward around the superior articular process, grooving 

 the upper surface of the posterior arch, passes through 

 a gap in the posterior occipito-atlantal ligament, winds 

 forward and unites with the opposite vertebral at the 

 anterior margin of the foramen magnum to form the 

 basilar artery. Seepage 158. 



For the relations of the artery in the suboccipital 

 triangle, see page 132. 



The artery is divided into the cervical, vertebral, occip- 

 ital (see page 132), and intracranial portions. 



The cervical portion is the part of the artery before 

 it enters the vertebral foramen. It lies in the interval 

 between the longus colli and scalenus anticus muscles, 

 and upon the transverse process of the seventh cervical 

 vertebra and sympathetic nerve. In front of it are the 

 vertebral and internal jugular veins, the inferior thyroid 

 artery, and, on the left side, the thoracic duct crosses it 

 from within outward. 



The vertebral portion is that part of the artery in transit 

 through the vertebral foramina, where it is surrounded by 

 a venous plexus and sympathetic filaments. 



