Which type of pneumocytes are specialized for producing surfactant and are able to regenerate?

• A. Type 1
• B. Type 2
• C. Both
• D. None

Answer: (B)

Two main pneumocyte types line the alveoli. The cell type that makes surfactant and can replenish the lining is the Type II pneumocyte. They are cuboidal cells that produce and store surfactant in lamellar bodies and secrete it to reduce surface tension, preventing alveolar collapse. Importantly, they also serve as progenitor cells: after injury they can proliferate and differentiate into Type I cells to restore the gas-exchange surface. Type I cells are thin and optimized for gas exchange but do not produce surfactant and have limited regenerative capacity. So the combination of surfactant production and the ability to regenerate points to Type II pneumocytes.