972 



THE VASCULAE SYSTEM. 



Veins of the Medulla Oblongata. Deep veins of the medulla oblongata issue 

 from its substance and end in a superficial plexus. This plexus is drained by an 

 anterior and a posterior median vein and by radicular veins. 



The anterior median vein is continuous below with the corresponding vein of the 

 spinal medulla ; it communicates above with the plexus on the surface of the pons. 



The posterior median vein is continuous below with the posterior median vein 

 of the spinal medulla, from which it ascends to the lower end of the fourth 

 ventricle, where it divides into two branches which join the inferior petrosal sinus 

 or basil ar plexus. 



The radicular veins issue from the lateral parts of the plexus and run with the 

 roots of the last four cerebral nerves ; they end in the inferior petrosal and occipital 

 sinuses or in the upper part of the internal jugular vein. 



SINUS DUR.E MATRIS. 



The venous sinuses of the cranium are spaces between the layers of the dura mater ; 

 and they are lined with an endothelium which is continuous with the endothelium 

 of the veins. They receive the veins of the brain, communicate frequently with the 



Inferior sagittal sinus Great cerebral vein (Galen) 



Straight sinus 



Superior petrosal sinus 



avernous sinus 



Facial nerve 



Posterior auricular 

 artery 



Transverse sinus 



Occipital sinus 

 Sup. oblique muscle 



Occipital artery 

 Descending branch 

 of occipital artery 



Vertebral artery 

 Semispinalis capitis 

 muscle (O.T. corn- 

 plexus) 

 Suboccipital nerve 



Sterno-mastoid 

 muscle 



Splenius capitis 

 muscle 



External carotid 

 artery 



arotid gland 

 Stylo-hyoid muscle 



Hypoglossal nerve 



Internal carotid artery 

 Digastric muscle (posterior belly) 



Longissimus capitis muscle Accessory nerve Internal Sterno-mastoid " Common carotid artery 

 (O.T. trachelo-mastoid) jugular vein. artery 



FIG. 787. DISSECTION OF THE HEAD AND NECK, showing the cranial blood sinuses and the upper part of 



the internal jugular vein. 



meningeal veins and with veins external to the cranium, and terminate directly or 

 indirectly in the internal jugular vein. Some of the cranial blood sinuses are 

 unpaired, others are paired. 



Unpaired Sinuses. These are the superior sagittal, the inferior sagittal, the 

 straight, the anterior and posterior intercavernous, and the basilar. 



