Azygos venous system
Updates to Article Attributes
The azygos (venous) system is a collective term given to the H-shaped configuration of the azygos, hemiazygos, accessory hemiazygos veins and left superior intercostal vein.
It is responsible for draining the thoracic wall and upper lumbar region via the lumbar veins and posterior intercostal veins1.1 It also provides important collateral circulation between the superior and inferior vena cava should they become obstructed.2.
Gross anatomy
Azygos vein
The azygos vein initially arises at the union of the right ascending lumbar vein and the right subcostal vein around T12. It enters the thorax via the aortic hiatus in the diaphragm and ascends posteriorly alongside the vertebral bodies, arching over the right main bronchus at T5-T6 and enters the superior vena cava (SVC) at T42.2 The azygos vein receives the lower 8 posterior intercostal veins and is joined by the right superior intercostal vein above. The accessory
Development
The azygos venous system initially arises from the supracardinal veins embryologically. The right supracardinal vein becomes the azygous vein, while the left supracardinal vein becomes the hemiazygos vein.3
Variant anatomy
The anatomy of the azygos system is often variable, especially the configuration of the hemiazygos and accessory hemiazygos veins.
The azygos vein can rarely drain into the right brachiocepalic vein, right subclavian vein, intrapericardial SVC or directly into the right atrium.4
that drain much of the posterior thoracic wall and some mediastinal structures. The anatomy of the azygos system is often variable, especially the configuration of the hemiazygos and accessory hemiazygos veins.
It provides an important collateral pathway for venous return to the heart in the event of IVC or SVC obstruction.
-<p>The <strong>azygos (venous) system</strong> is a collective term given to the H-shaped configuration of the <a href="/articles/azygos-vein">azygos</a>, <a href="/articles/hemiazygos-vein">hemiazygos</a>, <a href="/articles/accessory-hemiazygos-vein">accessory hemiazygos veins</a> and <a href="/articles/left-superior-intercostal-vein">left superior intercostal vein</a>. It is responsible for draining the thoracic wall and upper lumbar region via the lumbar veins and posterior intercostal veins.<sup>1 </sup>It also provides important collateral circulation between the superior and inferior vena cava should they become obstructed.<sup>2</sup></p><h4>Gross anatomy</h4><h5>Azygos vein</h5><p>The <a href="/articles/azygos-vein">azygos vein</a> initially arises at the union of the right ascending lumbar vein and the right subcostal vein around T12. It enters the thorax via the aortic hiatus in the diaphragm and ascends posteriorly alongside the vertebral bodies, arching over the right main bronchus at T5-T6 and enters the superior vena cava (SVC) at T4.<sup>2 </sup>The azygos vein receives the lower 8 posterior intercostal veins and is joined by the right superior intercostal vein above. The accessory</p><h4>Development</h4><p>The azygos venous system initially arises from the supracardinal veins embryologically. The right supracardinal vein becomes the azygous vein, while the left supracardinal vein becomes the hemiazygos vein.<sup>3</sup></p><h4>Variant anatomy</h4><p>The azygos vein can rarely drain into the right brachiocepalic vein, right subclavian vein, intrapericardial SVC or directly into the right atrium.<sup>4</sup></p><p> </p><p>that drain much of the posterior thoracic wall and some mediastinal structures. The anatomy of the azygos system is often variable, especially the configuration of the hemiazygos and accessory hemiazygos veins. </p><p>It provides an important collateral pathway for venous return to the heart in the event of <a href="/articles/ivc-obstruction">IVC</a> or <a href="/articles/superior-vena-cava-obstruction">SVC obstruction</a>. </p>- +<p>The <strong>azygos (venous) system</strong> is a collective term given to the H-shaped configuration of the <a href="/articles/azygos-vein">azygos</a>, <a href="/articles/hemiazygos-vein">hemiazygos</a>, <a href="/articles/accessory-hemiazygos-vein">accessory hemiazygos veins</a> and <a href="/articles/left-superior-intercostal-vein">left superior intercostal vein</a>.</p><p>It is responsible for draining the thoracic wall and upper lumbar region via the lumbar veins and posterior intercostal veins <sup>1</sup>.<sup> </sup>It also provides important collateral circulation between the superior and inferior vena cava should they become obstructed <sup>2</sup>. </p><h4>Gross anatomy</h4><h5>Azygos vein</h5><p>The <a href="/articles/azygos-vein">azygos vein</a> initially arises at the union of the right ascending lumbar vein and the right subcostal vein around T12. It enters the thorax via the aortic hiatus in the diaphragm and ascends posteriorly alongside the vertebral bodies, arching over the right main bronchus at T5-T6 and enters the superior vena cava (SVC) at T4 <sup>2</sup>.<sup> </sup>The azygos vein receives the lower 8 posterior intercostal veins and is joined by the right superior intercostal vein above.</p><h4>Development</h4><p>The azygos venous system initially arises from the supracardinal veins embryologically. The right supracardinal vein becomes the azygous vein, while the left supracardinal vein becomes the hemiazygos vein.<sup>3</sup></p><h4>Variant anatomy</h4><p>The anatomy of the azygos system is often variable, especially the configuration of the hemiazygos and accessory hemiazygos veins. </p><p>The azygos vein can rarely drain into the right brachiocepalic vein, right subclavian vein, intrapericardial SVC or directly into the right atrium.<sup>4</sup></p>
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