Airway Anatomy, Physiology, and Inflammation

Approximately 10,000 l of air and 8,000 l of blood transit the respiratory system each day driven by small pressure gradients developed in response to rhythmic contraction and relaxation of striated muscle under both voluntary and involuntary control of the central nervous system. Matching of air- and blood flow results from central and local reflexes responding to both internal and external stimuli and subsequently controlling the pumps, as well as the smooth muscle in walls of the airways and blood vessels. A wide range of neural and immune mechanisms protect the lungs against environmental insults, and many are adaptive in nature, resulting in memory that increases sensitivity and responsiveness upon repeated exposure to stimuli. In over 10 % of the population, the responses to environmental stimuli become pathological, resulting in excessive sensitivity and aberrant responses to both specific and nonspecific stimuli, and culminate in physical remodeling of the airways and lungs. Prevention, definitive diagnosis, and effective treatment of the disorders require a better understanding of the mechanisms underlying excessive responses to environmental stimuli.