Respiratory epithelial cells line the respiratory tract from trachea to bronchi into bronchioles and alveolar sacs. The primary functions of the respiratory epithelium, depending on their origin, is to moisten, protect the airway tract from potential pathogens, infections and tissue injury, and facilitate gas exchange. The respiratory epithelium in trachea and bronchi is pseudostratified and primarily consists of three main cell types – cilia cells, goblet cells, and basal cells. The ciliated cells are located across the apical surface and facilitate the movement of mucus across the airway tract. The goblet cells produce and secrete mucous to trap pathogens and debris within the airway tract. Basal cells are progenitor cells that differentiate into cells types found within the epithelium. Basal cells respond to injury of the airway and subsequently differentiate to restore a healthy epithelial cell layer.
- Goblet cells – Secrete mucus to maintain epithelial moisture and trappathogens or particulates
- Basal cells – Differentiate into other cell types to restore a healthy epithelial cell layer
- Cilia cells – Move back and forth, carrying mucus up and out of the respiratory tract