| The upper airways (UAW), which include the pharyngeal and laryngeal airway, lie at an important crossroads for functioning in vertebrae. Through the collapsible pharyngeal airway, we breathe, swallow food, eject potentially harmful contents from our stomach, and, in the case of ruminates, eructate. The narrower and less collapsible laryngeal airway is an important site of the regulation of airflow, protection of lower airways, and in humans, vocalization. With respect to these functions, the motions during respiration differ considerably to the movement during swallowing. Consequently, the UAW has come to be understood as a physiological time sharing system for its many opposing functions requiring a diverse and complicated control and activation of the muscles to regulate pharyngeal and laryngeal dimensions. The site of the control and integration of these opposing functions primarily lie in the brainstem.;In conclusion, the work herein advances the understanding of the activation and control of the pharyngeal and laryngeal muscles in maintaining airway patency and the apparent opposing functions associated in the interaction between swallowing and breathing. The connection between these otherwise opposite areas of work is simply the upper airway. It is within this locus of the body that an integration of many important functions occurs every minute within all mammals. However, the different interactions between swallowing and breathing reported between goats, cats, and humans suggest different functional connections between the neurons of the RCPG, SCPG, efferent and afferent systems. This pattern may be a result of the differences in anatomy of the UAW, gastrointestinal system, and development. The proposed extensions to the Balances of Forces to the UAW and the analyses of the interaction between swallowing and breathing together allows an in-depth view of the nature and type of relationship between the physiological functions under physiological conditions without knowing a priori the specific neuroanatomical basis of this interaction. Therefore, by assessing the nature and limits of the coupling between theses pattern generators in a wide range of whole and reduced animals preparations, we could clarify the adaptations of the central neural circuitry to a variety of anatomy and functional requirements of the upper airway in different species and during development. (Abstract shortened by UMI.)... |
