ABSTRACT
The lung is in direct contact with a total of 10,000 L of inhaled air daily, and all of the microorganisms, hazardous gases, and particulates suspended in this air. The conducting airways and alveoli are endowed with overlapping mechanical, cellular, and immunologi cal methods of clearing or neutralizing these foreign materials. Most of the time, the lung maintains its sterility and prevents entry of threatening substances to the circulation with out invoking an inflammatory response that would injure the lung’s delicate architecture. The details of these defense mechanisms, and the problems that occur when they fail are covered in subsequent chapters. (See Chaps. 5 and 18.)
Air Movement for Sound Generation and Other Behaviors We sometimes forget the importance of the respiratory system in other human behaviors. The movement of air across the vocal cords allows speech-the unique human ability that facilitates rich interactions with others in our families and society. [One is reminded of how this is taken for granted when we struggle to understand an awake but intubated patient in the intensive care unit (ICU)]. The movement of air past the lips is essential for some forms of music (wind instruments), occupations (glass blowing), and, at least in the past, the study of chemistry and biology (mouth pipetting!). These activities illustrate the remarkable versatility of the respiratory system. While performing continuous and life-sustaining gas exchange, this movement of air simultaneously permits these voluntary behaviors. No wonder that respiratory disease can be so incapacitating.
