Regarding lung diseases, one of the following is true?

Correct Answer: D

Rationale: Per Poiseuille's law (R ∝ 1/r^4), a 10% airway diameter increase reduces resistance by ~40%, not increases it false. COPD (e.g., emphysema) is common due to smoking, not least false. Pulmonary fibrosis, restrictive, reduces compliance, not airway resistance (obstructive) false. In fibrosis, FEV1/FVC is ≥80% (normal or higher) as both FEV1 and FVC drop proportionally true, unlike obstructive diseases (<70%). This ratio's preservation reflects restricted volume, not airflow, a key diagnostic feature, making it the true statement amid misconceptions about resistance and prevalence.

Correct Answer: B

Rationale: A bronchopulmonary segment is a functional lung unit supplied by a segmental (tertiary) bronchus (A), segmental pulmonary artery (E, implied), nerves (C), and lymphatics (D), all within its connective tissue boundaries. The segmental bronchus delivers air, the artery supplies blood, and nerves and lymphatics manage innervation and drainage. However, pulmonary veins (B) are not segment-specific; they run intersegmentally, collecting blood from multiple segments into larger lobar veins, not confined within a single segment's borders. This venous drainage pattern ensures efficient oxygenation return but excludes B from being a defining component of the segment's structure, unlike the artery and bronchus, which are segmentally discrete. Thus, B is the exception.

Correct Answer: D

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

Correct Answer: B

Rationale: The esophagus is lined with stratified squamous non-keratinized epithelium (B), protecting against abrasion from food while retaining flexibility. Simple squamous (A), a single thin layer, suits diffusion (e.g., alveoli), not mechanical stress. Stratified squamous keratinized (C) is in skin, with a tough, dry layer unsuitable for the moist esophagus. Simple columnar (D) lines the stomach and intestines for absorption, not esophageal function. B fits its multilayered, non-keratinized nature resists wear from swallowing, unlike the others, which serve different physiological roles.

Correct Answer: A

Rationale: Endothelium, lining blood vessels, is simple squamous epithelium (A), a single flat layer facilitating diffusion and minimizing friction. Simple cuboidal (B) lines tubules (e.g., kidney), not vessels. Stratified squamous (C) is protective (e.g., skin), too thick for endothelium. Transitional (D) stretches in the bladder, not relevant here. A is correct simple squamous' thinness suits endothelial gas and nutrient exchange, unlike the others' structures.