Читать книгу The Esophagus - Группа авторов - Страница 113

Swallowing is controlled by a network of neurons in the brainstem that form a swallowing pattern generator (SPG), which can produce sequential and rhythmic motor activity [4]. The SPG has complex connections to higher regions in the midbrain and the cerebral cortex and to the motor nuclei of cranial nerves serving over 50 different muscles along the swallowing pathway. Peripheral sensory input from the mouth, pharynx, and esophagus feed into the SPG and modulate its response to the nature of the bolus ingested. The SPG can be activated by cortical input when a swallow is voluntarily initiated, or triggered by peripheral sensory input in a reflexive swallow or secondary peristalsis. Thus, the SPG programs sequential motor output to the muscles along the entire swallowing pathway.

The SPG is not a single unit. Three functional stages of voluntary swallows – oral, pharyngeal, and esophageal – occur in sequence to move the bolus out of the mouth, through the pharynx and into the esophagus [5]. Each functional stage has its own central pattern generator within the SPG; these are linked together with each stage activating the next [6]. The SPG and its components are essential for a number of coordinated physiologic functions: (i) efficient propulsion of the bolus through the entire swallowing pathway; (ii) elevation of the larynx and closure of the laryngeal inlet for airway protection; (iii) initiation of peristalsis at the pharynx or different levels in the esophagus independent of voluntary swallowing; (iv) contraction and relaxation of the UES and LES; (v) deglutitive and distal inhibition; and (vi) coordination with reflexes connecting swallowing to respiratory, cardiovascular, and gastrointestinal physiology.