Posterior intercostal arteries

The posterior intercostal arteries are arteries that supply blood to the intercostal spaces.

There are eleven posterior intercostal arteries on each side.
 * The 1st and 2nd posterior intercostal arteries arise from the supreme intercostal artery, a branch of the costocervical trunk of the subclavian artery.
 * The lower nine arteries are the aortic intercostals, so called because they arise from the back of the thoracic aorta.

The right aortic intercostals are longer than the left, on account of the position of the aorta on the left side of the vertebral column; they pass across the bodies of the vertebrae behind the esophagus, thoracic duct, and azygos vein, and are covered by the right lung and pleura.

The left aortic intercostals run backward on the sides of the vertebrae and are covered by the left lung and pleura; the upper two vessels are crossed by the left superior intercostal vein, the lower vessels by the hemiazygos vein.

Opposite the heads of the ribs, the sympathetic trunk passes downward in front of them, and the splanchnic nerves also descend in front by the lower arteries.

Each artery then divides into an anterior and a posterior ramus.

A given posterior intercostal artery travels along the bottom of the rib with its corresponding posterior intercostal vein, as well as the intercostal nerve of the given space. The vein is superior to the artery, and the intercostal nerve is inferior to it.