By Christopher L. B. Lavelle
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Extra info for Applied Oral Physiology
4) Xth nerve to the intrinsic muscles of the larynx and oesophagus. The cervical oesophagus may receive two efferent supplies, one from the recurrent laryngeal and another from the pharyngo-oesophageal nerve arising from proximal to the nodose ganglion or Disordered swallowing from an oesophageal branch of the external laryngeal portion of the superior laryngeal nerve. Sequentially timed discharges from the medullary centre mediate the movement of the bolus through successive levels of the oesophageal musculature.
G. to the genioglossus and geniohyoid muscles). Thus a functional deglutition centre appears to exist, having selective mechanisms for activation by appropriate stimuli. These have a defined spatiotemporal code, with interconnection of component cells resulting in a virtually invariable sequence of excitation and inhibition so that swallowing is the same regardless of its manner of initiation and with precision of organization resulting in control over relevant motor neurones. Corollaries of these features are that feedback regulation is not necessary for swallowing to proceed, that the output of the centre is highly stable, and that activity in the centre exerts inhibition upon possibly competing centres.
Movement of the bolus from the mouth to the stomach occurs in an organized fashion only if the necessary neuromuscular and neuroregulatory controls are intact. The inherent complexity of the 40 Deglutition processes of deglutition probably predisposes its delicately balanced neural control to potential failure from a myriad of disease enitities. Most disorders of deglutition are not without cause, however, and a few examples are considered below to illustrate the scope of the complex nature of deglutition.