Pulmonary surfactant, whose deficiency causes respiratory distress syndrome, is produced by which cells?

Answer: A. Type 2 pneumocytes

Surfactant and RDS

Surfactant is produced by type 2 pneumocytes.

Function

• Surfactant reduces alveolar surface tension, stabilising alveoli of different sizes so they do not collapse (by Laplace's law, small alveoli would otherwise empty into larger ones).
• Without surfactant the lungs cannot expand and collapse, producing RDS.

Clinical correlation

• Surfactant production increases with gestational age, so RDS risk falls as gestation advances (~100% <28 weeks, ~2% at 35-36 weeks).
• Antenatal corticosteroids accelerate surfactant production; exogenous surfactant treats established RDS.

Why the others are wrong

Type 1 pneumocytes form the thin gas-exchange surface; goblet/ciliated cells line conducting airways; alveolar macrophages are immune cells - none produces surfactant.