Club cells (400X)

Club cells, also known as clara cells, are primarily found in the terminal bronchioles, which are the smallest airways leading to the respiratory bronchioles. They are less abundant in larger airways.

The club cells produce a surfactant-like substance that prevents the bronchioles from collapsing when a person exhales. The epithelium lining the bronchioles, including the presence of club cells, is typically composed of simple cuboidal or non-ciliated columnar cells as seen in this image. Unlike the ciliated cells found in larger airways, club cells lack cilia on their surface.

Club cells often have a dome-shaped or rounded nucleus, which is a characteristic feature when observed under a microscope.

Club cells contain secretory granules at their apical (top) surface, where Clara cell secretory protein (CCSP) or uteroglobin is stored before being released. These granules contribute to the secretory function of club cells.