Accessory hemi-azygos vein
Vena hemiazygos accessoria
A vein on the left side of the upper thoracic vertebrae that drains the upper left posterior intercostal spaces into the azygos vein.
At a glance
- English
- Accessory hemi-azygos vein
- Latin (TA2)
- Vena hemiazygos accessoria
- System
- Vein
- Region
- Trunk
- Side
- Single, on the midline
About the accessory hemi-azygos vein
The azygos system carries blood from the back of the chest wall to the superior vena cava. On the right it is a single azygos vein, but on the left it is usually split into two parts: the hemi-azygos vein below and the accessory hemi-azygos vein above. The accessory vein is the upper of the two.
It runs downwards on the left side of the bodies of the middle thoracic vertebrae, behind the descending aorta and in front of the heads of the ribs. It collects the posterior intercostal veins of the upper and middle left intercostal spaces below those drained by the left superior intercostal vein, and it often receives the left bronchial veins. Above, it commonly connects with the left superior intercostal vein. At about the level of the eighth thoracic vertebra it crosses to the right, behind the aorta, the oesophagus and the thoracic duct, to end in the azygos vein. Sometimes it joins the hemi-azygos vein instead, and the two cross together.
Its pattern varies a good deal, and on imaging it can be mistaken for an enlarged lymph node beside the aorta. Together with the rest of the azygos system it forms a bypass between the inferior and superior venae cavae. When either cava is blocked, the accessory hemi-azygos vein can widen greatly to carry blood around the obstruction. Surgeons operating on the descending aorta or the oesophagus from the left side of the chest meet it behind the aorta.
Course and drainage
- Begins at
- Formed by the posterior intercostal veins of the upper and middle left intercostal spaces, often linked above with the left superior intercostal vein.
- Drains into
- Crosses behind the aorta at about the eighth thoracic vertebra to end in the azygos vein, or sometimes in the hemi-azygos vein.
- Drains
- Drains the upper and middle left posterior chest wall and, often, the left bronchial veins.
Anthromica
See the accessory hemi-azygos vein where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
