| | BLOOD SINUSES OF THE CRANIUM. 839 
BLOOD SINUSES OF THE CRANIUM. 
The venous sinuses of the cranium are spaces between the layers of the dura mater; 
they are lined by an endothelium which is continuous with the endothelium of the 
veins. They receive the veins of the brain, communicate frequently with the 
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 longitudinal, the inferior longi- 
tudinal, the straight, the circular, and the basilar. 
The superior longitudinal sinus (sinus sagittalis superior) commences in the 
Inferior longitudinal sinus Vena magna Galeni 
Superior 
longitudinaly 
sinus \/, 
Aavernous sinus 
3 ze: Via : fy i Facial nerve 
Posterior auricular 
artery 
Lateral sins 
Occipital sinus ~ \\~ 
Sup. oblique muscle —~ 
nm . . x 
Occipital artery — \ 
Princeps cervicis artery 
xternal carotid 
Vertebral artery ——7 : artery 
Complexus muscle — Parotid gland 
Suboccipital nerve ert : Stylo-hyoid muscle 
Sterno-mastoid - 
muscle 
Splenius NPA cs, 
muscle 
~Hypoglossal nerve 
Internal carotid artery 
Digastric muscle (posterior belly) 
Ji 
Trachelo- 
- in erne Sterno-mastoic id ar 
raetaidnanccle Spinal Internal Sterno-mastoid Common carotid artery 
accessory nerve jugular vein artery 
Fic. 582,—DIssEcTION OF THE HEAD AND NECK, showing the cranial blood sinuses and the upper part of the 
internal jugular vein. 
anterior fossa of the cranium, at the crista galli, where it communicates through 
the foramen cecum with the veins of the nasal cavity or with the angular vein. 
It passes upwards, then backwards, and finally downwards in the convex margin of 
the falx cerebri, grooving the frontal, parietal, and upper part of the occipital 
bones. As it descends it passes slightly to the right side, and it ends at the level 
of the internal occipital protuberance by becoming the right lateral sinus. Instead 
of passing to the right, it occasionally turns to the left, and ends in the left lateral 
sinus. In either case its termination is associated with a well-marked dilatation, the 
torcular Herophili, which marks a confluence of sinuses, and which is lodged in a 
depressionat one side of the internal occipital protuberance. The torcularis connected, 
across the protuberance, by an anastomosing channel with a similar dilatation, which 
marks the junction of the straight sinus with the lateral sinus of the opposite side. 
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