Final answer:
Type II pneumocytes are the cells that secrete pulmonary surfactant, reducing surface tension within the alveoli and aiding lung function.
Step-by-step explanation:
The cell that secretes pulmonary surfactant is the type II pneumocyte. These cells are cuboidal epithelial cells interspersed among the type I alveolar cells and are responsible for the production of surfactant, which is critical for reducing the surface tension within the alveoli and preventing collapse during expiration. Without sufficient production of surfactant, as can occur with premature infants, there would be difficulty inflating the lungs due to increased surface tension.