Question 127

Question:

An infant is born prematurely at 32 weeks in respiratory distress. A chest X-ray shows signs of neonatal respiratory distress syndrome (RDS) and the infant is treated with exogenous surfactant. Which of the following types of pulmonary cells makes surfactant?

Correct Answer: B.  Type II alveolar cells

Surfactant is made by type II alveolar cells and stored in lamellar bodies within these cells. They start developing after 24 weeks gestation, which is one of the major reasons birth before 24 weeks is not compatible with life. Type I alveolar cells make up the majority of the alveolar surface. Capillary endothelial cells secrete angiotensin-converting enzyme (ACE). Clara cells are mostly found in the primary bronchioles and contain P450 enzymes to detoxify harmful chemicals in the lungs. Pseudocolumnar ciliated cells line the trachea, creating a “muco-ciliary escalator” to expel toxins/dust in the upper airways.