Describe venous drainage into the azygos system.
Describe venous drainage into the azygos system.
The term azygos comes from greek word meaning unpaired or single. The venous drainage of thorax comes with two challenges. First is the heart which occupies the mediastinum meaning there is no caval access for the posterior intercostal veins at that space due to the superior and inferior vena cava draining into the right atrium of the heart. The second challenge is the superior vena cava within the mediastinum is one of the most anteriorly oriented vasculature, meaning the intercostal veins will have their greatest drainage into the posterior intercostal veins which would have to be conveyed through the entire depth of the mediastinum to get to the superior vena cava. The evolutionary solution to this issue is the azygos system. The azygos system conducts the majority of blood from the walls of the thorax.
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