Mots Croisés Respiratory System CrosswordVersion en ligne Test your knowledge of the breathing system terms. par July 1 Tiny air sacs where gas exchange occurs between air and blood. 2 A dome-shaped muscle that contracts to expand the chest during breathing. 3 Two main tubes that branch from the trachea, conducting air into the lungs. 4 The windpipe that carries air from the throat to the lungs. 5 The voice box that routes air and contains the vocal cords. 6 A vital gas required for cellular energy production used during respiration. 7 The cavity behind the nose and mouth that connects to the larynx and esophagus. 8 Small air passages that lead to the alveolar sacs. 4 2 8 6 7 1 5 3