抄録
The closure of the airway by the larynx has three functional meanings: the first is the prevention of error in deglutition, the second, trapping of the exhaled air flow inside the thoracic cavity; and the third and last, the phonation. These three functions were all present in the mammals in the early Tertiary period, ca.65 million years ago. The second function, air trapping, enables the fixation of the thoracic cage, which is essential for obtaining the supporting points for the shoulder girdle musculatures during movements of the upper extremities. This anatomical innovation is originated in the three-dimensional, discontinuous arboreal habitat of the early mammals, and further elaborated in the tree-dwelling primates as the safety device to prevent falling from the tree. The specificity of the primate larynx is the completely closed anterior glottis during the air trapping. Although the complete closure of the anterior glottis is emphasize in the modern human as the adaptation to the production of primary tones, its functional origin goes back to the three-dimensional locomotor adaptation in the Tertiary arboreal primates.
