The cuboidal alveolar cells with lamellar bodies (1–2 μm in diameter) are responsible for producing which substance?

The cuboidal alveolar cells with lamellar bodies (1–2 μm in diameter) are responsible for producing which substance?

• A. Epinephrine
• B. Collagen type I
• C. Surfactant
• D. IgG

Answer: (C)

Cuboidal alveolar cells that contain lamellar bodies are type II pneumocytes. Their job is to synthesize and secrete pulmonary surfactant, a mixture of phospholipids (notably dipalmitoylphosphatidylcholine) and surfactant proteins stored in lamellar bodies and released into the alveolar space. Surfactant lowers surface tension at the air–liquid interface, preventing alveolar collapse during respiration. These cells also serve as precursors to type I pneumocytes after injury. Other substances listed come from different tissues (epinephrine from the adrenal medulla, collagen type I from fibroblasts, IgG from plasma cells), not from these alveolar cells.

Cuboidal alveolar cells that contain lamellar bodies are type II pneumocytes. Their job is to synthesize and secrete pulmonary surfactant, a mixture of phospholipids (notably dipalmitoylphosphatidylcholine) and surfactant proteins stored in lamellar bodies and released into the alveolar space. Surfactant lowers surface tension at the air–liquid interface, preventing alveolar collapse during respiration. These cells also serve as precursors to type I pneumocytes after injury. Other substances listed come from different tissues (epinephrine from the adrenal medulla, collagen type I from fibroblasts, IgG from plasma cells), not from these alveolar cells.