The passages through which air enters and leaves the body WordNet 3.0 & Open English WordNet

The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. Wikipedia

Part of the respiratory system through which air flows. Wikipedia Disambiguation

The part of the anatomy involved with the process of respiration Wikidata

The structures and passages involved with intake, expulsion, and exchange of oxygen and carbon dioxide in the vertebrate body. OmegaWiki

The passages, divided into an upper and a lower part, through which air enters and leaves the body, including the mouth, nose and nasal passages, pharynx, larynx, trachea, bronchi and conducting bronchioles, sometimes further including the respiratory bronchioles, alveolar ducts and alveoli. Wiktionary

Air passages of the body. Wiktionary (translation)