Dictionary of Allergies .. Bronchial secretions

Bronchial secretions are arranged into two layers on the epithelial surface. A two micron viscous or gel layer overlies a five-six micron watery or sol phase that extends to the epithelial surface. This watery phase contains surfactant derived from type two alveolar cells, arranged in lamellae and, in part, foamy droplets which may assist in inhibiting stickiness, and by regulating the water content of the sol phase, assist transport of the viscous secretions.

The gel phase transports deposited organic and inorganic dust particles deposited from the inhaled air as well as cells which have entered the airway secretions via the bronchial wall or from the alveolar system

References

Morgenroth, K., Wettengel, R., Newhouse, M.: Bronchial Asthma. Boehringer Ingelheim, Int. GmbH., 1987