There are eleven posterior intercostal arteries on each side. Each artery divides into an anterior and a posterior ramus.
Origin • The 1st and 2nd posterior intercostal arteries arise from the
supreme intercostal artery, a branch of the
costocervical trunk of the
subclavian artery. The SICA descends vertically. It passes lateral to the
cervicothoracic ganglion. It passes in between the pleural cupula, and anterior border of the neck of rib I. It then passes anterior to the necks of ribs II-III. • The remaining nine arteries arise from (the posterior aspect of) the
thoracic aorta.
Course and relations Each posterior intercostal artery travels along the bottom of the rib alongside its corresponding
posterior intercostal vein and
intercostal nerve; the vein is superior to the artery, and the nerve is inferior to it. The mnemonic "VAN" is commonly used to recall their order from superior to inferior. The right aortic intercostals are longer than the left because 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. The
sympathetic trunk (opposite the heads of the ribs) and
splanchnic nerves pass anterior to the arteries. == See also ==