ABSTRACT
The air around us is full of particles. With each breath we take, particles enter the nose and mouth. Particles may deposit at any point along their pathway by diffusion or deposition. They may impact on outer surfaces and never enter the body. If particles do enter, they may deposit on a multitude of surfaces beginning with the interior of the nose or mouth. The particles pass into the esophagus and into the bronchi where pathways branch off to different locations. As they continue their entry through the respiratory tract, their pathway gets even more tortuous as the tubules get smaller and smaller, until they terminate in the pulmonary alveoli.
