Anterior intercostal arteries

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

Gross Anatomy

The 1^st to 6^th anterior intercostal arteries arise directly from the lateral aspect of the internal thoracic artery. The 7^th to 9^th arise from the musculophrenic artery, a branch of the internal thoracic artery.

In each intercostal space, the anterior intercostal artery divides into paired branches:

• the larger (main) branch courses laterally in the upper aspect of their respective intercostal space between the internal and innermost intercostal muscles, below the intercostal vein and above the intercostal nerve (mnemonic "VAN"), protected by the costal groove of the rib above.
• the smaller (collateral) branch descends into the lower aspect of their respective intercostal space and courses laterally between the internal and innermost intercostal arteries. Here they are not offered protection by the rib above.

In the 2 most inferior intercostal spaces (10^th and 11^th spaces), the anterior intercostal artery is absent, with the posterior intercostal artery supplying each space solely.

Branches

As these arteries course laterally within the intercostal spaces, they give off a variable number of small perforating cutaneous branches. In the lateral aspect of the thoracic wall, the artery anastomoses with branches of the posterior intercostal artery.

Supply

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