666 



THE BLOOD-VASCULAR SYSTEM 



(d) The basivertebral veins [vv. basivertebrales] (fig. 524) collect the blood from the 

 cancellous tissue of the bodies of the vertebrae, and consist of a tunica intima only. They take 

 a radial direction converging to the transverse vessels connecting the longitudinal vertebral 

 sinuses. They communicate with the anterior external plexus and with the intercostal veins. 



3 The intevertebral veins [vv. intervetebrales] (fig. 524), emerge from each longitudinal 



Fig. 525. — The Vertebral Venous Plexuses. (After Henle.) 



Occipital vein 



fjT'^'Deep cervical veins 



Intervertebral vein 



Venous rete 

 Dura mater spinalis 



sinus and pass out through the intervertebral or anterior sacral foramina. They open into the 

 vertebral, intercostal, lumbar or sacral veins according to region and receive numerous tribu- 

 taries from the anterior and posterior external vertebral venous plexuses. They are instru- 

 mental in draining the venous sj'stcm of the vertebral column and spinal cord. 



3. THE INTERNAL MAMMARY VEIN 



The internal mammary voin [v. mammaria intorna] is formed by the union of 

 the venie comitantes corrospondinp; to the superior epigastric and musculo-phrenic 

 arteries. The right and left internal mammary veins pass upward, in company 

 with the corresponding arteries, to oixni into the right and left innominate 

 resj)ectively. 



Tributaries. — In addition to the superficial veins of the thorax, the internal 

 mammary veins receive the anterior intercostal, anterior bronchial and peri- 

 cardiac veins. 



The superior epigastric vein [v. opigastrica superior] assists in the drainage of the subcu- 

 taneous abdominal veins [vv. subcutaneic alxlominis]. 



The anterior bronchial veins [vv. bronchialos antcriores] arise in the bronchial walls and 

 communicate with the tracheal and posterior bronchial veins. 



