ABSTRACT
Inhaled particles may land on the surface of the lungs’ airspaces. Upon making contact with the airway or alveolar wall, the processes of retention and clearance of these particles begin. The retention of particles depends on many factors, among these are (1) particle size, shape, solubility, surface chemistry, and elastic properties of both the particles and the lung surface; (2) the anatomical location of the deposition site (conducting airways, alveoli), which is important for the route and distance of particle clearance; (3) the structures the particle interacts with at the site of deposition, including the surfactant film at the air-liquid interface; the aqueous phase; free cells, such as macrophages, lymphocytes, and granulocytes; the epithelial cells; and dendritic cells that reside at the basal side of the epithelium. All these factors determine the fate of a deposited particle: the length of time it is retained before being cleared or dissolved. Hence, these factors are important for the beneficial or pathogenic potential of the retained particles.
