Veins of the vertebral column
In 1947 William Herlihy, an Australian anatomist, published a fascinating study entitled: “Revision of the Venous System: The Role of the Vertebral Veins.” His theme was to examine the anatomy of the spinal venous system and to relate it functionally to t
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In 1947 William Herlihy, an Australian anatomist, published a fascinating study entitled: "Revision ofthe Venous System: The Role of the Vertebral Veins." His theme was to examine the anatomy of the spinal venous system and to relate it functionally to the dynamics of the circulation. While the description of this complex venous system merits only abrief description in the 35th Edition of Gray's Anatomy (1973), Herlihy placed it in a new light in terms of its physiologic importance in the circulat6ry system of man. For this reason we have devoted considerable time to the preparation of specimens illustrating the outstanding anatomie features of these veins. The vertebral column has two plexiform systems of veins extending along its length. These are described CIS the external vertebral venous plexus es and the interna I vertebral venOl15 plexuses.
TUE EXTERNAL VERTEBRAL VENOUS PLEXUS The extern al vertebral venous plexus is su~ject to many variations in the spatial arrangements of its tributaries. Described in simplest terms, its main posterior branches form large veins wh ich relate themselves to the sides of the spinous processes and course forward across the laminae on each side toward the intervertebral foramina (Fig. 3.1). They coalesce outside the foramina with emerging intervertebral veins. Here they are joined also by anteriorly directed veins which drain the body wall, the conftuence forming segmental veins related to the sides of the vertebral bodies. These veins in the neck drain largely into the venae eomitantes of the vertebral arteries in front, while the posterior tributaries of this plexus join the deep cervical veins on each side. In turn, both these veins and the right and left vertebral veins
45 The blood stlpply of the vertebral (olumn and spinal wnl
drain into the brachiocephalic veins near the internal jugular entry points. In the thoracic region they are termed intercostal veins which, further anteriorly, join the azygos systems of longitudinally directed veins oflarge caliber. In the lumbar region they are known as the lumbar veins, corresponding to the named arteries in this region, but are connected by a variable series of longitudinally directed channels, the ascending lumbar veins and the lumbar azygos veins. The lower lumbar veins drain into the inferior vena cava while the azygos systems in the chest drain into the superior vena cava and left brachiocephalic veins. From a functional point of view, there are important anastomoses between the external vertebral venous system and certain of the visceral veins such as the pelvic plexus and the renal veins.
THE INTERNAL VERTEBRAL VENOUS PLEXUS This complex system of veins extends from the region of the sphenoidal clivus within the skulI, where it anastomoses with the sinuses at the base of the skulI, to the sacral region below. It is in two parts, the anterior internal vertebral venous plexus and the posterior internal vertebral venous plexus. Batson (1940) described the importance of its continuity with the prostatic plexus and noted
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