Bronchiolar and large alveolar cell in pulmonary phospholipid metabolism.

The nonciliated bronchiolar cells (Clara cells) lining the terminal airways actively secrete a phospholipid. In contrast, the large alveolar epithelial cells (type II, granular pneumonocyte) are active phagocytic cells. It is proposed that the Clara cell is the main source of pulmonary phospholipid production (presumably surfactant) while the large alveolar cell is responsible for its subsequent breakdown.