Posterior intercostal arteries

The intercostal spaces are supplied by pairs of anterior and posterior intercostal arteriesand the anterior intercostal arteries.

Gross Anatomy

The first two intercostal spaces are supplied by the superior intercostal artery and the remaining nine spaces are supplied by separate branches from the descending thoracic aorta ¹. The right sided arteries are longer as the aorta lies onto the left side of the bodymidline.  They They pass in front of the vertebravertebrae and behind the azygos venous system, oesophagus and thoracic duct. The left sided arteries pass backwardsrun 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 ininto the anterior and posterior ramusrami.  The The anterior ramus runs along the costal groove, accompanied by an intercostal nerve and intercostal vein.  The The vein lies superior to the artery and the nerve inferior to the arteryit (mnemonic "VAN").  It then divides into four branches - :

• collateral intercostal,
• lateral cutaneous
• mammary, mammary and
• muscular ¹.

The posterior ramus gives off branches which anastamose with other vessels to supply the spinal cord and soft tissue structures of the back.

Supply

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