respiratory tract, the complex of organs and structures that performs the pulmonary ventilation of the body and the exchange of oxygen and carbon dioxide between ambient air and blood circulating through the lungs. It also warms the air passing into the body and assists in the speech function by providing air for the larynx and the vocal cords. Every 24 hours about 500 cubic feet of air (150 m3) passes through the respiratory tract of the average adult, who breathes in and out between 12 and 18 times a minute. The respiratory tract is divided into the upper respiratory tract and the lower respiratory tract. Also called respiratory system. See also Color Atlas of Human Anatomy, pp. A28-A31.
