basic normal venous anatomy of the chest
The deeply situated brachial veins and the superficially situated basilic and cephalic veins of the upper extremities converge centrally to form the axillary veins. The axillary veins become the subclavian veins at the lateral aspects of the first ribs. The superficially situated external jugular veins drain from the neck into the subclavian veins. More centrally, the subclavian veins and the internal jugular veins from the neck converge to form the brachiocephalic veins (longer on the left than on the right), which then join to form the superior vena cava (SVC), finally leading to the right atrium. The vertical segment of the azygos vein is located to the right of the thoracic spine and drains superiorly toward its horizontal segment, which enters the posterior SVC above the right mainstem bronchus. The hemiazygos venous system is located toward the left of the thoracic spine and has variable communication with the azygos system.