Final answer:
Type II alveolar cells secrete pulmonary surfactant, which reduces surface tension in the alveoli. This cell type is essential for proper lung function.
Step-by-step explanation:
The type II alveolar cell is responsible for secreting pulmonary surfactant, a substance that reduces the surface tension of the alveoli. It is composed of phospholipids and proteins and is essential for proper lung function. Other cells in the alveolar wall include type I alveolar cells, which are responsible for gas exchange, and alveolar macrophages, which remove debris and pathogens from the alveoli.