Posterior intercostal arteries

The intercostal spaces are supplied by pairs of anterior and posterior intercostal arteries. The posterior intercostal arteries arise from the aorta and in part supply the spine and spinal cord and thus are considered segmental arteries.

Gross Anatomy

There are 11 paired arteries that constitute the posterior intercostal arteries. The first two intercostal spaces are supplied by the superior intercostal artery, and the remaining nine are supplied by separate branches from the descending thoracic aorta ¹. The right sided arteries are longer as the aorta lies to the left of the midline. They pass in front of the vertebrae and behind the azygos venous system, oesophagus and thoracic duct. The left sided arteries run posteriorly adjacent to the vertebrae and enter into the intercostal space.

The superior intercostal artery is the descending branch of the costocervical trunk, which arises from the second part of the subclavian artery ².  It enters the thorax anterior to the neck of the first rib with the sympathetic trunk on its medial side.

Branches

The posterior intercostal artery divides into the anterior and posterior rami. The

The anterior ramus runs along the costal groove, accompanied by an intercostal nerve and vein. The vein lies superior to the artery and the nerve inferior to it (mnemonic "VAN").  It then The anterior ramus divides into four branches¹:

• collateral intercostal
• lateral cutaneous
• mammary, and
• muscular¹

The posterior ramus (dorsal branch) gives off three branches which anastomose with other vessels to supply the :

• spinal
• medial musculocutaneous
• lateral musculocutaneous

The spinal cordbranch gives off radicular, segmental medullary, and soft tissue structures of the back/or radiculomedullary branches.

Supply

Along with the anterior intercostal arteries, the posterior intercostal arteries supply the muscles and skin within the intercostal spaces as well as the parietal pleura ³.