internal thoracic artery, one of a pair of arteries that arise from the first portions of the subclavian arteries, descend to the margin of the sternum, and divide into the musculophrenic and superior gastric arteries at the level of the sixth intercostal space. The artery supplies the pectoral muscles, the breasts, the pericardium, and the abdominal muscles. In females, it is also called the internal mammary artery.
