We have two, we have the inferior and the superior vena cava. Now, if our arteries actually carry blood away from the heart, then the veins always carry blood to the heart and away from the cells, the tissues and organs of our body. Most of the time, veins carry deoxygenated blood, but sometimes in the case of the left and the right pulmonary vein, they actually carry oxygenated blood to the left atrium of our heart. Now, what about the structure? What about the anatomy of the vein? So as it turns out, veins also have these same three layers.