A 35-year-old woman has experienced multiple bouts of severe necrotizing pneumonia since childhood, with Haemophilus influenza, Staphylococcus aureus, pseudomonas aeruginosa, and Serratia marcescens cultured from her sputum. She now has a cough productive of large amounts of purulent sputum. On physical examination, there is a dullness to percussion with decreased breath sounds over the right mid to lower lung fields. A chest radiograph shows areas of right lower lobe consolidation. A bronchogram shows marked dilation of right lower lobe bronchi. Which of the following mechanisms is the most likely cause of her disease?

Correct Answer: D

Rationale: Recurrent inflammation with bronchial wall destruction (D) causes bronchiectasis here (Page 29, Ans: D). Repeated infections scar and dilate bronchi (100 mL sputum/day), per bronchogram. Congenital defects (A) are rare. Eosinophils (B) fit asthma. Carcinoma (C) masses, not dilates. D's chronic damage unlike A's static cause explains progression, per document.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: The trachea (D) is the windpipe . This 10-12 cm cartilaginous tube connects larynx to bronchi, conducting air. The pharynx (A) is a throat passage. Bronchioles (B) are smaller airways. The larynx (C) houses vocal cords. D's structural role 16-20 C-shaped rings warms and humidifies air (Page 5, Q11A), unlike A's dual role or B's distal position, per anatomy texts.

Correct Answer: D

Rationale: In infant respiratory distress syndrome (IRDS), surfactant deficiency (A) reduces compliance (C), needing higher pressures. Alveoli collapse (atelectasis), not overexpand (D, false), due to high surface tension (T) without surfactant (Q7). Premature lungs (28 weeks viable, Q15) lack type II pneumocytes' lamellar bodies, raising T (normal 30 dynes/cm to 50+), dropping C (< 0.1 L/cm H2O). D's burst claim contradicts collapse B's pressure (e.g., 20-30 cm H2O) fights this, and positive pressure aids, per physiology.

Correct Answer: B

Rationale: Alveoli (B) have the largest cross-sectional area (~70 m^2), minimizing resistance . Trachea (A) is wide (~2.5 cm) but singular. Bronchi (D) branch, increasing area (~0.1 m^2), yet less than alveoli. Bronchioles (C) narrow (1 mm), but 300 million alveoli dwarf them (Poiseuille's law: R ∝ 1/r^4). Resistance dominates in medium airways (bronchi), not alveoli, where flow slows for exchange. B's vast area unlike A's single tube cuts velocity (1-2 cm/s vs. 100 cm/s in trachea), per physiology's airflow distribution.