Type II alveolar cells are primarily responsible for producing which substance?

• A. Surfactant
• B. Mucus
• C. Alveolar macrophages
• D. Interstitial fluid

Answer: (A)

Type II alveolar cells, also known as type II pneumocytes, play a crucial role in the respiratory system, primarily by producing surfactant. Surfactant is a lipoprotein complex that reduces surface tension within the alveoli, the tiny air sacs in the lungs where gas exchange occurs. By decreasing surface tension, surfactant helps prevent the alveoli from collapsing during exhalation, thereby maintaining proper lung function and facilitating easier breathing.

Additionally, surfactant contributes to the overall stability of the alveoli and enhances pulmonary compliance, which is essential for efficient gas exchange. This function is particularly vital in premature infants who may have underdeveloped lungs and insufficient surfactant production, leading to conditions such as neonatal respiratory distress syndrome.

The production of mucus is primarily the function of goblet cells and submucosal glands in the airway, while alveolar macrophages are immune cells that reside in the alveoli to help clear pathogens and debris. Interstitial fluid is part of the interstitial space surrounding cells in the lung and is not specifically produced by type II alveolar cells.