superior sagittal sinus 



diploic vein (anterior temporal), 

 superior ophthalmic 



cavernous sinus 



internal maxillary 



posterior facial 



external maxillary {anterior facial) 



— lingual vein 



superior thyroid 



anterior jugular 



middle thyroid 



inferior thyroid 



inferior sagittal sinus 

 great cerebral vein 



sinus rectus 



superior petrosal 



sinus 

 occipital vein 

 occipital sinus 

 transverse sinus 



sigmoid sinus 



posterior auricular 



vertebral 

 posterior external jugular 



internal jugular 

 external jugular 



-subclavian 

 Figure 11-31. Veins of the head In man. (After Tandler) 



Paralleling the internal jugular but lying superficially in 

 the neck is the external jugular vein. The branches of the 

 external jugular drain most of the outer regions of the head. 

 A posterior facial division, paralleling the superficial tem- 

 poral artery, receives diploic veins from the skull bones. A 

 large posterior auricular enters the skull at the mastoid 

 foramen to connect with the transverse or sigmoid sinus. 

 The large anterior facial vein, which parallels the external 

 maxillary artery, has mandibular, inferior labial, superior 

 labial, and orbitonasal branches. 



Draining a part of the blood of the anterior facial is an 

 anterior jugular vessel, lying superficially in the neck, just 

 lateral to the midline. The vessels of either side connect 

 ventrally or posteriorly and are joined by a stem with the 

 external jugular. The external jugulars join the subclavian 

 veins, then fuse to form the superior vena cava. 



In the neck is also a vertebral vein, a reticulum of chan- 

 nels enclosing the vertebral artery. This helps drain the oc- 

 cipital region and the internal vertebral system. 



Lying within the brain cavity are bilateral channels with 

 cavernous sinuses to either side of the sella turcica. Supe- 

 rior and inferior ophthalmic veins and their branches con- 

 nect with the cavernous sinus through the orbital fissure. 



There is a cross connection through the floor of the sella 

 turcica between the cavernous sinuses; this cross connection 

 encircles the infundibular stem. There is also a cross con- 

 nection behind the dorsum sella; this enters the basilar 

 plexus which extends back through the foramen magnum 

 into the vertebral canal. The cavernous sinuses connect on 

 either side with the sigmoid sinuses through superior and 

 inferior petrosal sinuses. 



In the description of the skull it was pointed out that the 

 main venous drainage channel of the brain cavity was not 

 necessarily through the jugular foramen, for it may be 

 through the postglenoid foramen. In the dog (Figure 1 1-32) 

 the postglenoid commissural vessel drains the transverse sinus 

 into the external jugular. The internal jugular is small as is 

 the sigmoid sinus. 



EMBRVOLOGicAL DEVELOPMENT In the development of the 

 venous channels, at first there is a reticulum of channels 

 passing above and below the ganglia and roots of the cranial 

 nerves. From these channels, which can be seen in the 

 10-mm pig, the anterior cardinal forms. This extends for- 

 ward above the vagus nerve, passes lateral to that nerve 

 near its ganglion, lateral to the ninth ganglion and root. 



CIRCULATION IN THE HEAD 



361 



