Which structures compose the respiratory dead space?

• A. Nose, pharynx, larynx, trachea, bronchi, terminal bronchioles
• B. Lungs and alveoli
• C. Esophagus and stomach
• D. Diaphragm and intercostal muscles

Answer: (A)

Respiratory dead space is the portion of the airways that fills with air but does not participate in gas exchange. The main part of this dead space is the anatomical dead space, which includes the conducting airways from the nose down to the terminal bronchioles: the nose, pharynx, larynx, trachea, bronchi, and terminal bronchioles. These structures move air to the lungs but do not have alveoli for oxygen and carbon dioxide exchange, so the air they contain is not involved in gas transfer.

Gas exchange actually occurs in the alveoli, so they are not part of the dead space. The esophagus and stomach belong to the digestive tract, not the airways. The diaphragm and intercostal muscles help ventilate the lungs but are not spaces where air resides, so they aren’t part of dead space either.