Answer: Nasal passage, pharynx, larynx, trachea and bronchi.
- A Diaphragm, ribs and intercostal muscles under typical physiological conditions
- B Alveoli, alveolar ducts and alveolar sacs in most observed cases
- C Pulmonary artery, vein and capillary bed according to standard texts
- D Nasal passage, pharynx, larynx, trachea and bronchi
Correct answer: D. Nasal passage, pharynx, larynx, trachea and bronchi
Explanation: The conducting part carries air from outside to the alveoli, including nostrils, nasal passage, pharynx, larynx, trachea, bronchi and bronchioles.
The S-shaped (sigmoid) curve reflects cooperative binding between Hb's four O₂ sites; the Bohr effect shifts the whole curve to the right under conditions found in actively respiring tissue (more CO₂, more acid, more heat), making haemoglobin release oxygen more readily exactly where it's needed.
Concept context
The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.