Final answer:
Type II pneumocytes, also known as Type II alveolar cells, are the cells in the lung that secrete pulmonary surfactant, a substance vital for reducing surface tension in the alveoli.
Step-by-step explanation:
The cells of the lung that produce the substance that lowers surface tension are Type II pneumocytes. Type II alveolar cells, also known as Type II pneumocytes, are cuboidal epithelial cells that are interspersed among the more numerous type I alveolar cells within the alveolar walls. These cells are crucial as they secrete pulmonary surfactant, a substance composed of phospholipids and proteins that significantly reduces the surface tension within the alveoli. This reduction in surface tension is critical for preventing the alveoli from collapsing and ensures they can efficiently expand during inhalation and prevent collapse during exhalation. Without sufficient pulmonary surfactant, the alveoli would face difficulty in functioning properly, as seen in premature infants who may suffer from respiratory distress syndrome due to inadequate surfactant production.