A neonate within 4 hours of bih presented with severe respiratory distress. He appears to be dyspneic, tachypneic, and cyanotic with severe retractions of the chest. On examination, grunting is present along with use of the accessory muscles. Neonate also appears to have scaphoid abdomen and increased chest wall diameter. There is evidence of shift of the point of maximal cardiac impulse from its original location to the right side. Chest x ray of the neonate Defect in development of which pa of the responsible structure is causing this condition of the baby?