The respiratory organs are those organs through which air flows during pulmonary ventilation. They include the nose, oral cavity, pharynx, larynx, trachea, bronchi, bronchioles, and lungs. We can breathe through the mouth, but the nose is the primary entrance and exit for air. The mouth is a backup, essential only when the nasal passage is blocked, as by a cold, or when we are struggling to get in as much oxygen as possible, as during vigorous exercise. Normally, air flows out the mouth only whenn we are talking.