402 



Arteries of the Head. 



A. cerebri posterior 

 A. cerebelli superior 



A. communicans posterior 



auditiva interna 

 A. cerebelli inferior posterior 

 A. spinalis posterior 

 I A. meningea posterior (from the a. pharyngea ascendens) 

 ' I Tentorium cerebelli 



A. cerebri , 

 media 



A. cerebri 

 anterior 

 A. com- 

 municans ~ 

 anterior 



Hypophysis - 



- Dura mater 



Ramus meningeus 

 A. yertebralis 



Ramus spinalis 

 a. vertebralis 



N. cervicalis II 



Ramus ad pontem 

 A. cerebelli inferior anterior 



A. spinalis anterior 



^\ 



447. Arteries of the base of the brain in their 

 relation to the base of the skull 



after removal of the brain ; right half of the skull, viewed from the left. 



(The falx cerebri has been completely removed, the tentorium cerebelli partially. The a. meningea 

 posterior and the ramus meningeus a. vertebralis have been drawn upon the dura mater.) 

 1. A. vertebralis (see also Figs. 441, 444, 448 and 449) arises from the upper circum- 

 ference of the a. subclavia and passes, at the lateral margin of the m. longus colli, lateralward 

 and behind the a. carotis communis, curved slightly backward to the foramen transversarium 

 of the 6th cer\acal vertebra, then through the foramina transversaria of the 5*^1 2^^^ cervical 

 vertebra, in front of the emerging cervical nerves, almost perpendicularly upward; it is next 

 curved markedly lateralward to the foramen transversarium of the atlas and goes medianward 

 in the sulcus arteriae vertebralis (see Kgs. 216, 221 and 341) in a curve behind the massa 

 lateraMs atlantis, bridged over by fibers of the membrana atlantooccipitalis posterior and then 

 passes backward covered directly by the mm. obliquus capitis superior and rectus capitis posterior 

 major. Between the atlas and os occipitale it then perforates the dura mater, bends upward, 

 furward and medianward in front of the medulla oblongata to the upper surface of the clivus 

 and unites with the vessel of the same name of the other side approximately in front of the 

 posterior margin of the pons to form the unpaired a. basilaris. This goes upward and forward 

 upon the clivus in the sulcus basilaris of the pons and, at the anterior margin of the pons, 

 below the substantia jierfurata posterior and at the upper margin uf the dorsum sellae, divides 

 into its two terminal branches, the aa. cerebj'i jjostcriores. Branches of the a. vertebralis: 



a) Rami spinales, from tlae cervical portion, go through tlie foramina intervertebralia to the 



canalis vert<>bralis and its contents. They give off lirancjies to the neighboring muscles. 



b) Ramus meningeus arises a. littl<^ in front of the point where the vessel passes through 



the dura mater and extends, through the foramen magnum, upward to the dura mater 

 of the posterior fossa of the skull. 



