Answer: Insufficient surfactant production (type II alveolar cells immature), causing alveolar collapse.
- A Excess surfactant production flooding the alveolar lining with lipid film material in the majority of cases studied
- B Insufficient surfactant production (type II alveolar cells immature), causing alveolar collapse
- C Premature over-development of alveolar septa restricting the gas exchange surface area as widely reported
- D Pulmonary edema resulting from cardiac overload unrelated to surfactant levels present in standard practice
Correct answer: B. Insufficient surfactant production (type II alveolar cells immature), causing alveolar collapse
Explanation: Neonatal RDS (hyaline membrane disease): premature type II alveolar cells do not produce adequate surfactant. Surface tension causes alveoli to collapse on expiration. Treated with exogenous surfactant.
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.