Respiratory organs are involved in the human respiratory system, in which air travels through the mouth, nasal passage , and trachea (windpipe), respectively. the trachea has cartilage rings to prevent it from collapsing. From the trachea. The air passes through the right and left bronchi (singular : bronchus), which carry air into millions of tiny sacs knows as alveoli (singular : alveolus),which have a lot of tiny blood vessels called capillaries. Gas exchange occurs in the alveoli or air sacs.