The Anterior intercostal branches of internal thoracic artery
supply the upper five or six intercostal spaces
. The internal thoracic 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 intercostal arteries from the aorta.
They are at first situated between the pleura and the Intercostales interni, and then between the Intercostales interni and externi.
They supply the intercostal muscles and, by branches which perforate the Intercostales externi, the Pectoral muscles and the mamma.