260 



THE VASCULAR SYSTEMS 



it is accompanied by a sympathetic plexus, it is in front of the 

 spinal nerves, and it crosses the suboccipital nerve on the atlas. 



Branches. The cervical branches are muscular, to the deep 

 cervical region, joining the occipital and deep cervical; and the 

 lateral spinal, entering the intervertebral foramina. 



The cranial branches include: 



(a) The posterior meningeal, to the falx cerebelli and cerebellar 

 fossae. 



(6) The anterior spinal, along the front of the medulla, joins 

 its fellow to form the upper part of the anterior median artery 

 of the cord. This is a small vessel which runs in the anterior 

 median fissure of the cord, beneath the pia mater, as far as the 

 cauda equina. 



FIG. 42 



Plan of the branches of the right subclavian artery. 



(c) The posterior spinal descends along the posterior nerve 

 roots to the cauda equina. It is formed in a similar manner to 

 the anterior, but it is bilateral. 



(d) The poster oinferior cerebellar divides under the cerebellum 

 into two branches. The inner runs to the notch between the 

 hemispheres; the outer, to their under surface and the choroid 

 plexus of the fourth ventricle, joining the superior cerebellar. 



The basilar artery, formed by the two vertebrals, runs to the 

 upper border of the pons, and divides into the two posterior 

 cerebrals. It gives off the following branches: 



