DIPLOIC AND MENINGEAL VEINS. 



969 



VENOUS SINUSES AND VEINS OF THE CRANIUM AND OF ITS 



CONTENTS. 



The venous channels met with in the cranial walls and cranial cavity are : 



(1) The diploic veins, which lie in the spongy tissue between the outer and 

 inner tables of the cranial bones. 



(2) The meningeal veins, which accompany the meningeal arteries in the outer 

 layer of the dura mater. 



(3) The veins of the brain, which lie between the folds of pia mater and in the 

 subarachnoid space. 



(4) The cranial venous sinuses, channels which are situated between the outer 

 and inner layers of the dura mater; they receive the blood from the terminal 

 cerebral veins. 



DIPLOIC AND MENINGEAL VEINS. 



Venae Diploicse. The diploic veins are anastomosing spaces in the spongy 

 tissue of the flat bones of the skull ; they are lined with endothelium. The number 

 of efferent vessels which emerge from the diploic spaces is not constant, but usually 

 there are at least four on each side viz., a frontal, two temporal, anterior and 

 posterior, and an occipital. 



The frontal diploic vein is one of the most constant ; it drains the anterior part 



Posterior temporal 

 diploic vein 



Occipital diploic 



vein 



Anterior temporal diploic vein 



Frontal diploic vein 



FIG. 786. THE VEINS OF .THE DIPLOE. 



of the frontal bone, passes through a small aperture in the upper margin of the 

 supra-orbital notch, and terminates in the supra-orbital vein. 



The anterior temporal diploic vein drains the posterior part of the frontal bone 

 and the anterior part of the parietal bone; it pierces the great wing of the 

 .sphenoid, and terminates either in the spheno-parietal sinus or in the anterior 

 deep temporal vein. 



The posterior temporal diploic vein drains the posterior part of the parietal 

 bone; it runs downwards to the posterior inferior angle of the parietal bone 

 and terminates in the transverse sinus, to which it passes either through a 

 foramen in the inner table of the parietal bone or through the mastoid foramen. 



