Clara cells are present in

cells of Clara - Some non-ciliated cells present predominantly in terminal bronchioles produce a secretion that spreads over the alveolar cells forming a film that reduces surface tension. These include the cells of Clara. Some functions attributed to cells of Clara include: Protection against harmful substances that are inhaled. Protection against development of emphysema by opposing the action of substances (proteases) that tend to destroy walls of lung alveoli. Stem cell function. REF : Inderbir Singh's Textbook of Human Histology, Seventh edition, pg.no. 235.