A 52-year-old woman from Mumbai undergoes elective left lower lobe lung resection for bronchogenic carcinoma. Intraoperatively, the surgeon notes that the left phrenic nerve is adherent to the tumor and must be sacrificed. Postoperatively, the patient develops orthopnea and dyspnea on exertion. On fluoroscopic examination of the diaphragm during respiration, the left hemidiaphragm moves paradoxically upward during inspiration. Which nerve was injured, and what is the embryological origin of the muscle it innervates?