Which immune cells are present in alveolar spaces that phagocytose debris?

Which immune cells are present in alveolar spaces that phagocytose debris?

• A. Alveolar macrophages line alveolar walls.
• B. Alveolar macrophages secrete surfactant.
• C. Alveolar macrophages form alveolar ducts.
• D. Alveolar macrophages are present in alveolar spaces and phagocytose debris.

Answer: (D)

Alveolar macrophages are the immune cells that reside in the alveolar spaces and perform phagocytosis of debris. They act as the dust cells of the lung, engulfing inhaled particles, dead cells, and bacteria that reach the air spaces to keep the delicate gas-exchange region clean. These cells originate from circulating monocytes and are a primary line of defense within the alveoli. Surfactant, the substance that reduces surface tension, is produced by type II pneumocytes, not by macrophages, and alveolar ducts are lined by epithelial cells rather than formed by macrophages.

Alveolar macrophages are the immune cells that reside in the alveolar spaces and perform phagocytosis of debris. They act as the dust cells of the lung, engulfing inhaled particles, dead cells, and bacteria that reach the air spaces to keep the delicate gas-exchange region clean. These cells originate from circulating monocytes and are a primary line of defense within the alveoli. Surfactant, the substance that reduces surface tension, is produced by type II pneumocytes, not by macrophages, and alveolar ducts are lined by epithelial cells rather than formed by macrophages.