THE VEINS OF THE BRAIN 



G53 



the sphenoid bone, the sinus communicates with the pterygoid plexus of veins; through the 

 venous plexus around the petrosal portion of the internal carotid [plexus venosus caroticus 

 internus], with the internal jugular vein; and through a venous rete which leaves the cranium 

 by the foramen ovale [rete foraminis ovahs] and by small veins passing through the foramen 

 lacerum medium, with the pterygoid and pharyngeal plexuses. 



(11) The spheno-parietal sinus [sinus sphenoparietalis] runs in a slight groove 

 on the under surface of the lesser wing of the sphenoid bone. It originates in 

 one of the meningeal veins near the apex of the lesser wing, and, running mediall}', 

 passes through the sphenoidal fold of dura mater above the third nerve into the 

 front part of the cavernous sinus. It generally receives the anterior temporal 

 veins from the diploe. 



Fig. 516. — The Venous Sinuses at the Base of the Brain. The dura mater has not been 

 removed. (After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.) 



Position of crista galli 

 Circular sinus \ 



Circular sinus \ 



Process of dura in foramen caecum 



Optic nerve 

 Ophthalmic vein 



Cavernous sinus. 



Connection with 

 the rete foraminis 

 ovalis 



Middle meningeal 

 artery 



Inferior petrosal ___ 

 sinus 



Internal carotid __ 

 artery 



Superior hulb of the _ 

 internal jugular 

 vein 



Transverse sinus 

 Mastoid vein 

 Vertebral artery 

 Fold of 



Optic nerve 



- Maxillary nerve 



Mandibular 

 nerve 



— Abducens nerve 



Superficial petrosal 

 nerve 



Facial nerve 



■^^ Acoustic nerve 



■ Glossopharyngeal 

 nerve 



■ Vagus nerve 



^ Accessory nerve 



Hypoglossal nerve 

 spinal nerve 



The petro-squamous sinus is occasionally present. It lies in a groove along the junction 

 of the petrous and squamous portions of the temporal bone. It opens posteriorly into the trans- 

 verse sinus at the spot where the latter enters on its sigmoid course. In front it sometimes, 

 though very rarely, passes through a foramen in the squamous portion of the temporal bone 

 between the mandibular fossa and the external auditory meatus into the temporal vein. 



3. THE VEINS OF THE BRAIN 



The veins of the brain present the following peculiarities: — (a) They do not 

 accompany the cerebral arteries. (6) Ascending veins do not, as in other situ- 

 ations, run with descending arteries, but with ascending arteries, and vice versa. 

 (c) The deep veins do not freely communicate, {d) The veins have very thin 

 walls, no muscular coat, and no valves, (e) The veins opening into the sagittal, 

 and some of those opening into the transverse (lateral) sinus pour in their blood in 

 a direction opposite to the current in the sinuses, so impeding the flow in both 



