3.2.13 Inferior vena cava, azygos veins
Next we’ll look briefly at the inferior vena cava, which brings all the blood from the lower half of the body to the right atrium. The reason we’ll just look at it briefly is that within the thorax, the inferior vena cava has no length at all: it enters the right atrium as soon as it passes through the diaphragm.
To see the inferior vena cava, we’ll move the diaphragm downward, and move the heart to the left. Here’s the inferior vena cave. After coming up through the diaphragm it passes almost immediately into the lower part of the right atrium. It enters separately form the superior vena cava, which is here.
We’ll look at the course of the inferior vena cava below the diaphragm in the next section of this tape. Now we’ll look at the azygos vein and its tributaries.
Here’s the azygos vein, arching over the right main bronchus, and joining the superior vena cava. To see where it comes from, we’ll remove the heart, and all the other structures of the mediastinum.
Here’s where the azygos vein has been divided. The azygos vein begins below the diaphragm and runs up along the right side of the vertebral column. The azygos vein receives blood from the posterior and lateral parts of the chest wall. On the right side, the posterior intercostal veins empty directly into it. On the left side, the posterior intercostals empty into these two hemi-azygos veins which in turn empty into the azygos.