Internal thoracic aery is a branch of ?

Internal thoracic aeryIt arises from Ist pa of subclan aery and descends through anterior ends of upper six intercostal spaces lying 1.25 cm lateral to sternal margin.It divides into two terminal branches, musculophrenic and superior epigastric in 6th intercostal space.Branches of internal thoracic aery are (i) mediastinal branches, (ii) pericardial branches, (iii) sternal branches, (iv) pericardiophrenic branches, (v) anterior intercostal aeries (in upper six spaces), (vi) perforating branches, and (vii) two terminal branches, musculophrenic and superior epigastric.