The superior vena cava is (SVC) formed proximally by the confluence of the right and left brachio-cephalic veins in the superior mediastinum at the level of the right first costal cartilage. From there, the SVC runs for about 5-7cm inferiorly in a slightly anterior-medial orientation. It ends at the superior vena caval orifice in continuity with the right atrium at the level of the third right costal cartilage in the middle mediastinum. Superior to this point it becomes ensheathed by pericardium. Posteriorly, at the level of the second costal cartilage, the azygous vein runs anteriorly over the root of the right lung to merge with the posterior aspect of the SVC.
The brachiocephalic veins and the SVC represent the major veins in the superior mediastinum. They drain venous blood from the subclavian veins and internal jugular veins, thus providing venous blood return from both the territories of the upper extremities and the head and neck.
The right brachiocephalic vein is shorter than the left brachiocephalic vein. Usually near the convergence of the internal jugular vein and the sub-clavian vein the right brachiocephalic vein receives lymphatic supply from the right lymphatic duct, right jugular lymph trunk and subclavian lymph trunk.At the confluence of left subclavian vein and left internal jugular vein the left brachiocephalic additionally receives the inferior thyroid veins, the thoracic duct, the thymic veins and the superior intercostal vein.
The axillary vein is a continuation of the basilic vein from the arms. It extends along the chest to the first rib, where it becomes the subclavian vein. The cephalic vein belongs to the superficial venous system of the upper extremity. It merges with the axillary vein just before it becomes the subclavian vein.
Fig. 4. Direct contrast-enhanced MR venography of the upper extremity and central thoracic veins. Diluted (1:15) contrast agent was injected into a vein on the dorsum of the hand bilaterally. The data set shows normal filling of the left sided veins. On the right side an occlusion of the axillary/subclavian vein is well depicted. Note the prominent collateral veins on right side (arrows)
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