Posted by Amanda2 on August 15, 2013 at 14:39:28:
I had a few students ask me this morning about the thoracic collateral circulation, so here’s a quick summary of it all:
As we know, the anterior and posterior intercostal vessels anastomose along the midaxillary line within the thoracic wall. Due to this anastomosis, blood can be delivered to the descending aorta in an indirect fashion in case it cannot get there via the direct route (aka from the aortic arch). For example, in the case of an aortic coarctation, the aorta becomes narrowed due to the ligamentum arteriosum so blood flow to the descending aorta becomes decreased. However, because there is collateral circulation, blood can get to the descending aorta via an indirect route by going through the subclavian to the internal thoracic to the anterior intercostals to the posterior intercostals to the descending aorta.
Below is the list of where the intercostal arteries branch off from and where the intercostal veins drain to
Arteries
Posterior intercostal spaces
1-2: Supreme (highest) thoracic artery from costocervical trunk of
subclavian artery
3-11: Posterior intercostal arteries from the descending aorta
Anterior intercostal spaces
1-6: Internal thoracic artery from subclavian artery
7-9: Musculophrenic artery from internal thoracic artery
10-11: Superior epigastric from internal thoracic artery
Veins
Right posterior intercostal spaces
1: Supreme (highest) intercostal vein to brachiocephalic vein
2-4: Superior intercostal vein to arch of the azygous vein
5-11: Posterior intercostal veins to azygous vein
Left posterior intercostal spaces
1: Supreme (highest) intercostal vein to brachiocephalic vein
2-4: Superior intercostal vein to accessory hemiazygous vein, or
brachiocephalic vein, or coronary sinus
5-11: Posterior intercostal veins tochemiazygous vein
Anterior intercostal spaces
1-6: Internal thoracic vein
7-9: Musculophrenic vein
10-11: Superior epigastric vein