Respiratory system

Abstract

The main function of the respiratory system is to supply oxygen to the blood and eliminate carbon dioxide. The system (Fig. 14.1) must admit a maximal amount of air through a narrow inlet and a minimal volume of passageways. It must also distribute this air to the largest possible surface for gas exchange with blood. To do this the system has two functionally different parts, a conducting portion and a respiratory portion. The conducting portion includes nasal cavities with their associated olfactory mucosa (Fig. 14.2), paranasal sinuses, pharynx, larynx, trachea, bronchi, and bronchioles. It conducts air to the respiratory portion. The respiratory portion is composed of respiratory bronchioles, alveolar ducts, alveolar sacs, and some 300 million alveoli. Here gases are exchanged between air and blood. Table 14.1 lists some measurements of these components.