What do Clara (club) cells secrete?

• A. Mucus
• B. Surfactant
• C. Serous fluid
• D. The precursors for epithelial cells

Answer: (C)

Clara cells, or club cells, are specialized epithelial cells located in the bronchioles of the lungs. They play a crucial role in maintaining airway health and function. One of their primary functions is the secretion of various substances, which include proteins that act as protective agents in the airways.

The correct answer pertains to the secretion of serous fluid, which contributes to the overall maintenance of the airway lining. This fluid helps to keep the airways moist and facilitates the transport of secretions, thus playing a part in mucociliary clearance. Clara cells also produce other substances such as antioxidants and enzymes that aid in detoxifying harmful inhaled substances.

In the context of Clara cells' roles, they do not secrete mucus directly, nor do they produce surfactant, which is primarily secreted by type II alveolar cells. While Clara cells can give rise to progenitor cells that can differentiate into epithelial cells, they do not directly secrete epithelial cell precursors; instead, their secretory products mainly focus on maintaining airway surface health and protection.