ABSTRACT
The anatomy of the respiratory tract greatly influences its function (1). Additional factors, such as exercise, will result in further adaptation of the respiratory tract anatomy by increasing contraction of the accessory respiratory muscles to accommodate the increase in ventilation or exercise-induced hyperpnea. From a functional standpoint, it is helpful to separate the respiratory tract into the extrathoracic airways and the intrathoracic airways, with the former extending from the nose to the extrathoracic portion of the trachea.
