Identifying key lung structures in histological photomicrograph

Steps:

• Locate round structures with thick muscular walls: indicates artery.
• Identify collapsible vessels with thin walls: confirms vein presence.
• Spot cartilaginous rings in tubular epithelium: identifies bronchus.
• Check for absence of large ciliated tube with prominent cartilage: rules out trachea.

Why A is correct:

• Standard lung parenchyma sections contain arteries, veins, and bronchi for gas exchange support, but trachea is a singular midline structure excluded from peripheral tissue samples.

Why the others are wrong:

• B: Excludes all but trachea, ignoring vascular and bronchial elements essential to lung histology.
• C: Omits bronchus, a core airway structure visible in lung sections.
• D: Lacks artery and vein, which are integral to pulmonary circulation in tissue views.

Final answer: A