What type of cells secrete surfactant in the alveoli?

Surfactant in the alveoli is secreted by cuboidal cells, specifically known as type II alveolar cells or type II pneumocytes. These cells play a crucial role in maintaining the surface tension within the alveoli, which is essential for proper lung function. Surfactant is a lipoprotein complex that reduces surface tension, preventing the collapse of alveoli during exhalation and facilitating easier expansion during inhalation.

The structure of cuboidal cells allows them to effectively synthesize and secrete this complex surfactant material. In contrast, type I pneumocytes, which are squamous cells, primarily serve as a barrier for gas exchange and do not have the capacity to produce surfactant. Thus, the presence of cuboidal cells as the primary source of surfactant highlights their vital role in respiratory physiology and the maintenance of lung compliance.