Which statement about surfactant synthesis and secretion is true?

• A. Lung distension inhibits secretion
• B. Surfactant is produced by Type I cells
• C. Type II cells decrease secretion in response to beta agonists
• D. Type II cells are responsible for major pathways involved in surfactant metabolism

Answer: (D)

S surfactant metabolism happens mainly in type II pneumocytes. These cells are the production hub: they synthesize the phospholipid components (notably DPPC) and the surfactant proteins, process them through the cell’s secretory pathway, and package them into lamellar bodies for secretion into the alveolar space. They also handle recycling and turnover of surfactant after it has served its function. Type I cells, in contrast, are thin, form the gas-exchange surface, and do not synthesize surfactant. Additionally, beta-adrenergic stimulation tends to increase, not decrease, surfactant secretion, and lung inflation/stretch promotes secretion rather than inhibits it. So the statement that type II cells are responsible for major pathways involved in surfactant metabolism accurately captures their central role.