The Mechanism of the Larynx—II The epiglottis and closure of the larynx

Abstract

An anatomical, clinical and radiological study was made of the mechanism of closure of thelarynx. In swallowing there are some 5 components. These 5 components are normally closely integrated, but may be partially or wholly dissociated in unusual or abnormal circumstances. The larynx may also be closed partially or completely for many other reasons, including breath-holding, abdominal straining, and phonating. In all these circumstances the basic components of the mechanism employed are the same as for swallowing, except for the fact that the epiglottis is not turned down. All these components are used with different degrees and combinations to vary size, form and alignment of the laryngeal lumen in speech. The hyoid bone is also an important structure. Apposition of the thyroid cartilage to the hyoid bone is an essential component of laryngeal closure. By this means there may be introduced many variations in the shape and alignment of the laryngeal vestibule and vestibular folds, which must have considerable influence on function. The role of this mechanism in voice production was largely overlooked. The formation of the laryngeal ventricles and the changes inform and size of the vestibular folds are also described; it is considered that these influence the effective length of the vocal folds.