224 



THE HEAD AND NECK 



The Transverse Sinus runs laterally and slightly upwards 

 from the internal occipital protuberance ; grooving the occipital 

 bone. Its highest point is placed on the mastoid (postero- 

 inferior) angle of the parietal bone,, and it then turns downwards,, 

 forming a deep groove on the mastoid portion of the temporal 

 bone. Its horizontal part lies in the attached margin of the 

 tentorium cerebelll.(Fig. 68) , but its vertical portion lies in the 

 lateral wall of the! posterior cranial fossa and is situated behind 

 the tympanic . (mastoid) antrum (p. 214). At its termination 

 it runs medially and then forwards to reach the jugular 

 foramen, through which it passes to become continuous with 



Superior sagittal sinus 

 Fossae for occipital lobes 



Falx cerebri 



Straight sinus 



Transverse'sinus 



Fossae for cerebellum 



Transverse sinus 



Occipital sinus 



FIG. 68. Oblique Section through Posterior part of Skull, showing the 

 relationship of the Dura Mater to the Cerebral Sinuses. The fibrous 

 layer of the dura mater is shown in blue, and the serous layer in red. 



the internal jugular vein. It receives the mastoid emissary vein 

 (p. 216) and tributaries from the cerebellum and the lower part 

 of the lateral surface of the cerebrum. 



The transverse sinus corresponds roughly to the superior 

 nuchal (curved) line on the occipital bone. In mapping it out 

 on the surface it must be borne in mind that the sinus is about 

 one-third of an inch wide. It commences a little above the 

 external occipital protuberance and runs laterally to the asterion 

 (p. 218). In this part of its course the sinus presents a varying 

 degree of upward convexity, but the summit of its curve is 

 rarely higher than a point one ringer's breadth above the middle 

 of the line joining the external occipital protuberance to the 

 centre of the external acoustic (auditory) meatus. The descend- 



