Notes
Veins of the Trunk
Major veins of the thoracic and abdominal walls:
Common iliac veins
- Merge to form the inferior vena cava, which ascends through the thorax.
Iliolumbar vein
- Drains into the common iliac vein; it receives the 5th lumbar vein.
Ascending lumbar veins
- Drain into the common iliac veins; they ascend along the lumbar vertebrae.
Subcostal vein (which lies below the 12th rib)
- Drains into the ascending lumbar vein.
- Subcostal and ascending lumbar veins form the azygos vein, which drains directly into the superior vena cava, which also drains the brachiocephalic veins.
Azygos vein
- Receives venous drainage from the 11th to 4th right posterior intercostal veins.
Right superior intercostal vein
- Drains into the arch of the azygos vein; the right superior intercostal vein is the final tributary of the azygos vein before it drains into the superior vena cava.
Hemiazygos vein
- Merging of ascenidng lumbar and subcostal veins on left side of the body
- Hemiazygos vein ascends through the thorax, it drains the left posterior intercostal veins 11-8.
- Drains into the azygos vein.
- This venous junction connects drainage of the lower and upper torso regions.
Accessory hemiazygos vein
- Descends along the superior posterior thoracic wall on the left side of the body and typically drains into the azygos vein.
- Drains the 7th-4th posterior intercostal veins on the left side of the body.
Internal thoracic vein
- Drains into the brachiocephalic vein; it receives the musculophrenic vein and anterior intercostal veins.
Key Venous Drainage Points:
Posterior Abdominal Wall Drainage:
- 5 pairs of lumbar veins drain the posterior abdominal wall. These veins traverse the lumbar vertebrae; they have various drainage patterns, which we can organize as:
- The 5th lumbar vein drains into the iliolumbar vein; which drains into the inferior vena cava via the common iliac vein.
- The 3rd and 4th lumbar veins drain directly into the inferior vena cava: the major inferior conduit of deoxygenated blood-flow return to the heart.
- The 1st and 2nd lumbar veins drain into the ascending lumbar veins; which connect inferior and superior regions of the torso.
Thoracic Wall Drainage:
- 11 intercostal veins, which travel within the intercostal spaces with the arteries and nerves.
- Anteriorly, the intercostal veins drain into the internal thoracic vein; this vessel, which ascends through the internal thorax, drains into the brachiocephalic vein, superiorly.
- Posteriorly, the intercostal venous drainage is more complex (like that of the posterior abdominal wall) and depends on the location of the vessel:
The 1st intercostal vein typically drains directly into the brachiocephalic vein; however, it may drain with the
2nd and 3rd intercostal veins, which merge to form the superior (aka, supreme) intercostal vein; the right and left superior intercostal veins drain asymmetrically.
4th - 11th posterior intercostal veins drain into the azygos system, which comprises vertically oriented vessels that travel to the sides of the vertebral column deep within the thorax.
Clinical Correlation:
- The ascending lumbar veins provide a vital alternative pathway for venous return if the inferior vena cava becomes blocked.
- The azygos system also provides collateral venous drainage pathways in the case of obstruction of the superior vena cava.