The phrenic nerve originates with the cervical spinal roots C3, C4, and C5, and it is actually essential for initiating the respiration system. This nerve serves the two motor functions for diaphragm contraction and sensory features to the pericardium and mediastinal pleura, including the phrenic nerves.Màng b?m là b? ph?n ti?p xúc tr?c ti?p v?i