Anterior intercostal branches of internal thoracic artery

The anterior intercostal branches of the internal thoracic artery are paired arterial branches that arise from the internal thoracic artery (Internal mammary artery) to supply the anterior portions of the upper six intercostal spaces.

Origin and Course

The internal thoracic artery arises from the first part of the subclavian artery and descends along the inner surface of the anterior chest wall, approximately 1 cm lateral to the sternum. From this parent vessel, two small anterior intercostal branches arise at each of the upper six intercostal spaces one running along the lower border of the rib above and the other along the upper border of the rib below.

Distribution

• In intercostal spaces 1-6, the anterior intercostal branches originate directly from the internal thoracic artery.

• In intercostal spaces 7-9, the anterior intercostal branches arise from the musculophrenic artery, one of the two terminal branches of the internal thoracic artery (the other being the superior epigastric artery).

• The lower two intercostal spaces (10 and 11) typically lack anterior intercostal arteries.

Anastomoses

The anterior intercostal branches anastomose with the posterior intercostal arteries the upper two of which arise from the supreme (superior) intercostal artery, and the remaining from the thoracic aorta. This anastomotic network provides collateral circulation to the chest wall.

Supplied Structures

These branches supply the intercostal muscles, overlying skin and subcutaneous tissue, the parietal pleura, and, in females, contribute to the blood supply of the breast (particularly via the perforating branches of the 2nd through 4th intercostal spaces).