622 THE VASCULAR SYSTEMS 



the sixth cervical vertebra, 1 and ascends through the foramina in the transverse 

 processes of all the vertebrae above this. Above the upper border of the axis it 

 inclines outward and upward to the foramen in the transverse process of the atlas, 

 through which it passes; it then winds backward behind its articular process, 

 runs in a deep groove on the upper surface of the posterior arch of this bone (Fig. 

 16), and, passing beneath the posterior occipito-atlantal ligament (Figs. 224 and 

 227), pierces the dura and arachnoid, and enters the skull through the foramen 

 magnum. It then passes forward and upward, inclining from the lateral aspect 

 to the front of the medulla oblongata. It unites in the middle line with the vessel 

 of the opposite side at the lower border of the pons to form the basilar artery 

 (Fig. 449). 



Relations. At its origin it is situated behind the internal jugular and vertebral veins, and 

 is crossed by the inferior thyroid artery; it lies between the Longus colli and Scalenus anticus 

 muscles, having the thoracic duct in front of it on the left side. It rests on the transverse process 

 of the seventh cervical vertebra and the sympathetic cord. Within the foramina formed by 

 the transverse processes of the vertebra it is accompanied by a plexus of nerves from the inferior 

 cervical ganglion of the sympathetic, and is surrounded by a dense plexus of veins which unite 

 to form the vertebral vein at the lower part of the neck. It is situated in front of the cervical 

 nerves, as they issue from the intervertebral foramina. While winding around the articular 

 process of the atlas, it is contained in the suboccipital triangle a triangular space formed by 

 the Rectus capitis posticus major, the Obliquus capitis superior and the Obliquus capitis 

 inferior muscles. The suboccipital nerve here lies between the artery and the posterior arch of 

 the atlas. Within the skull, as the artery winds around the oblongata, it is placed between the 

 hypoglossal nerve and the anterior root of the suboccipital nerve, beneath the first digitation of 

 the ligamentum denticulatum, and finally ascends between the basilar process of the occipital 

 bone and the anterior surface of the medulla oblongata. 



Applied Anatomy. The vertebral artery has been tied in several instances. (1) For wounds 

 or traumatic aneurism; (2) after ligation of the innominate, either immediately to prevent hem- 

 orrhage, or later on to arrest bleeding where it has occurred at the seat of ligation. The oper- 

 ation of ligation of the vertebral is performed by making an incision along- the posterior border 

 of the Sternomastoid muscle, just above the clavicle. The muscle is pulled to the inner side, 

 and the anterior tubercle of the transverse process of the sixth cervical vertebra is sought for. 

 A deep layer of fascia being now divided, the interval between the Scalenus anticus and the 

 Longus colli muscles just below their attachment to the tubercle is defined, and the artery and 

 vein are found in the interspace. The vein is to be drawn to the outer side, and the aneurism 

 needle is passed from without inward. Drs. Ramskill and Bright have pointed out that severe 

 pain at the back of the head may be symptomatic of disease of the vertebral artery just before 

 it enters the skull. This is explained by the close connection of the artery with the suboccipital 

 nerve in the groove on the posterior arch of the atlas. Disease of the same artery has been also 

 said to affect speech, from pressure on the hypoglossal nerve where it is in relation with the 

 vessel, leading to paralysis of the muscles of the tongue. 



Branches. These may be divided into two sets those given off in the neck 

 and those within the cranium. 



Cervical Branches. Cranial Branches. 



Spinal rami, or Lateral spinal. Posterior meningeal. 



Muscular. Anterior spinal, or Ventral spinal. 



Posterior spinal, or Dorsal spinal. 



Posterior inferior cerebellar. 



Bulbar. 



The spinal branches (rami spinales) enter the vertebral canal through the inter- 

 vertebral foramina and divide into two branches. Of these, one passes along the 

 roots of the nerves to supply the spinal cord and its membranes, anastomosing 

 with the other arteries of the spinal cord; the other divides into an ascending and 



1 The vertebral artery sometimes enters the foramen in the transverse process of the fifth vertebra. Dr. 

 Smyth, who tied this artery in the living subject, found it, in one of his dissections, passing into the foramen 

 in the seventh vertebra. 



