 The internal thoracic artery (previously called as internal mammary artery) then divides into the superior epigastric artery and musculophrenic artery.The latter gives out the remaining anterior intercostal branches.Two in number in each space, these small vessels pass lateralward, one lying near the lower margin of the rib above, and the other near the upper margin of the rib below, and anastomose with the posterior intercostal arteries from the thoracic aorta.