The respiratory system permits the exchange of oxygen needed for cellular metabolism for carbon dioxide, which is a by-product of cellular metabolism. This chapter describes the location and function of the organs of the respiratory system and explains how they contribute to the overall function of the system (objectives 1-3). Respiratory and nonrespiratory air movements, respiratory volumes and capacities, and how normal breathing is controlled (objectives 4-9) are discussed. Gas exchange and transport, and oxygen utilization by the cell (objectives 10-13) are explained.

There are four events in respiration: (1) exchange of gas with the external environment, (2) diffusion of gas across the respiratory membrane, (3) transport of gas to and from the cell, and (4) diffusion of gas across the cell membrane for utilization of oxygen by the cell. An understanding of all these events and how they interact is basic to understanding how cells produce the energy necessary for life.