THE SPIXAL VEINS 



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of which runs along the posterior surface of the bodies of the vertebrae, anterior 

 longitudinal spinal veins. The other plexus, posterior longitudinal spinal veins, 

 is placed on the inner or anterior surface of the laminae of the vertebras. 



The anterior longitudinal spinal veins (sinus vertebrates longitudinales) consist 

 of two large, tortuous veins which extend along the whole length of the vertebral 

 column, from the foramen magnum, where they communicate with each other 

 by a venous ring around that opening and with the basilar and occipital sinuses 

 through the foramen, to the base of the coccyx, being placed one on each side 

 of the posterior surface of the bodies of the vertebrae along the margin of the 

 posterior common ligament. These veins communicate opposite each vertebra 

 by transverse trunks which pass beneath the ligament. Each transverse trunk 

 receives the large vena basis vertebrae (v. basivertebralis) from the interior of the 

 body of the vertebra. The anterior longitudinal spinal veins are least developed 

 in the cervical and sacral regions. They are not of uniform size throughout, 

 being alternately enlarged and constricted. At the intervertebral foramina they 



The extra-spinal veins. 



FIG. 516. Transverse section of a thoracic vertebra, 

 showing the spinal veins. 



FIG. 517. Vertical section of two thoracic vertebra?, 

 showing the spinal veins. 



communicate with the extraspinal veins, and with the vertebral veins in the neck, 

 with the intercostal veins in the thoracic region, and with the lumbar and sacral 

 veins in the corresponding regions. 



The posterior longitudinal spinal veins, smaller than the anterior, are situated 

 one on either side, between the inner surface of the laminae and the theca verte- 

 bralis. They communicate (like the anterior) opposite each vertebra by trans- 

 verse trunks, and with the anterior longitudinal veins by lateral transverse branches 

 which pass from behind forward. The posterior longitudinal veins, by branches 

 which perforate the ligamenta subflava, join with the extraspinal veins. From 

 them branches are given off which pass through the intervertebral foramina and 

 join the vertebral, intercostal, lumbar, and sacral veins. 



The intervertebral veins (vv. inter vertebrates) accompany the spinal nerves in 

 the intervertebral foramina, receive veins from the spinal cord, and join the 

 intra- and extraspinal veins. 



3. The veins of the bodies of the vertebrae (vv. basi 'vertebrates) emerge from 

 the foramen on the posterior surface of each vertebra and join the transverse 

 trunk connecting the anterior longitudinal spinal veins. They are contained 



