VERTEBRAL 



509 



Branches of the First Part of the Subclavian Artery 



THE VERTEBRAL ARTERY 



The vertebral artery, tlie first and largest branch, arises from the upper and 

 posterior })art of the first i)ortion of the subclavian, on the right side about 

 three-quarters of an inch (2 cm.) from the origin of the latter vessel from the 

 innominate, on the left side, from the most prominent part of the arch of the sub- 

 clavian, close to the inner edge of the scalenus anticus muscle. It first ascends to 

 the foramen in the costo-transverse process of the sixth cervical vertebra, and, having 

 passed through that foramen and those of the next succeeding cervical vertel)rse as 

 high as the axis, it turns outwards and tlien upwards to reach the foramen in the 



Fig. 342.— Scheme of the Left Veetebrae Akterv. (Walsham.) 

 The internal jugular and verteliral veins are Looked aside to exi^ose the artery. 



Right posterior cerebral artery 



Left posterior cerebral artery 



Basilar artery 



BASILAR PROCESS, OCCIPITAL BONE 



Intracranial portion of vertebral 



Rectus capitis lateralis muscle 



FIRST CERVICAL XERVE 



Commencement of vertebral vein 



SECOND CERVICAL NERVE 



Vertebral plexus of reins 



THIRD CERVICAL NERVE 



Vertebral /lorlion of vertebral artery 

 FOURTH CERVICAL NERVE 



Vertebral plexus of veins 

 FIFTH CERVICAL NERVE 



SIXTH CERVICAL NERVE 



Inferior thyroid artery 



Longus colli mutele 



Cervical portion of vertebral artery 



Internal jugular rein, liooked a little 

 aside 



Vertebral vein, cut 



Subclavian artery 



Right and left supe- 

 rior cerebellar 

 arteries 



OCCIPITAL BONE 



Keetus capitis pos- 

 ticus minor mus- 

 cle 



/iifal ] 0) ti07i of rertebral artery 



A 1 teria princeps cervicis 



Semispinalis colli muscle 



Deep cervical artery 



Scalenus anticus muscle, cut 

 Thyroid axis, hooked a little aside 

 Subclavia/i rein 



transverse process of the atlas; after passing through that forann^n it turns back- 

 wards behind the articular ])rocess lying in the groove on the jjosterior arch of the 

 atlas. It next ]»ierces the jiosterior occipito-atloid ligament and the dura mater, and 

 enters the cranium through the foramen magnum. Here it passes ui)wards, at first 

 lying by the side of tlie medulla, then in front of that structure, and terminates at 

 the lower portion of tlie pons Viy inosculating witli the vertebral of the opposite side 

 to form the basilar. 



The vertel)ral artery may be divided for purposes of description into four parts: 

 the first, or cervical, extending from its oriirin to the transverse jtrocess of the sixth 

 cervical vertebra: the second, or vertebral, situated in the intt'rvrrtebral foramina: 

 the third, or occipital, contained in the suboccipital triangle: and the fourth, or 

 intracranial, witliin tlie cranium. 



The first or cervical portion. — Tlie artery liere lies l)etween the scalenus 



