chapter  58
Anatomy of the larynx and tracheobronchial tree
ByNimesh N. Patel, Shane Lester
Pages 14

INTRODUCTION The human larynx protects the lower respiratory tract, provides a controlled airway, allows phonation and allows the generation of a high intrathoracic pressure for coughing and lifting. The evolution of the larynx provides an insight into its functional priorities. In its most primitive form, it can be found as a muscular sphincter around the entrance to the respiratory tract in the Bichir lungfish (Polypterus bichir), controlling the entry of water and the expulsion of air from the lungs. A further evolutionary variant is seen in the Mexican salamander, which possesses lateral cartilages that aid in opening and maintaining patency of the respiratory tract. The ability of the larynx to facilitate speech is only found in humans and represents a more specialized function of the larynx; it is, therefore, a very late evolutionary event.