Internal thoracic artery

The internal thoracic artery (previously known as internal mammal artery) arises from the subclavian artery near its origin.

It travels downward on the inside of the ribcage, approximately a centimeter from the sides of the sternum, and thus medial to the nipple. It is accompanied by the internal thoracic vein.

It runs deep to the external oblique, but superficial to the vagus nerve

It continues downward until it divides into the superficial intercostal artery and the inferior epigastric artery around the sixth costal cartilage.

Branches:

• Mediastinal branches
• Thymic branches
• Pericardiacophrenic artery - travels with the phrenic nerve
• Sternal branches
• Perforating branches
• Twelve anterior intercostal branches, two to each of the top six intercostal spaces. In a given space, the upper branch travelling laterally along the bottom of the rib until it anastomoses with its corresponding posterior intercostal artery. The lower branch of the space anastomoses with a collateral branch of the posterior intercostal artery.

After passing the sixth intercostal space, the internal thoracic artery splits into the following two terminal branches:

• Musculophrenic artery - roughly follows the costal margin
• Superior epigastric artery - continues the course of the internal thoracic artery, travelling downward into the abdominal wall