Swallowing and Esophageal Transport

Swallowing (deglutition) is the coordinated neuromuscular sequence that carries a bolus from the mouth, through the pharynx, and down the esophagus into the stomach. Esophageal transport is the peristaltic phase of that sequence: an orderly wave of contraction, timed with relaxation of the upper and lower esophageal sphincters, that moves the bolus through the esophagus and protects the airway during the act.

Definition

Swallowing is the sequential transfer of an ingested bolus from the oral cavity through the pharynx into the esophagus and stomach, and esophageal transport is its peristaltic phase, in which a coordinated contractile wave and sphincter relaxation propel the bolus toward the stomach.

Scope

This topic covers the normal physiology of swallowing — its oral, pharyngeal, and esophageal phases — together with the neural control that orchestrates them and the manometric description of esophageal peristalsis. It is a reference and educational entry on how transport works; the clinical evaluation and management of swallowing difficulty are treated elsewhere and are not the subject here.

Core questions

• What distinguishes the oral, pharyngeal, and esophageal phases of swallowing?
• How does the brainstem generate and sequence a swallow?
• How is esophageal peristalsis measured and described manometrically?

Key concepts

• Oral, pharyngeal, and esophageal phases
• Central pattern generator for swallowing
• Primary and secondary peristalsis
• Upper esophageal sphincter
• Lower esophageal sphincter relaxation
• Airway protection during swallowing

Mechanisms

Swallowing is divided into a voluntary oral phase that prepares and propels the bolus, an involuntary pharyngeal phase in which the airway is closed and the upper esophageal sphincter opens, and an esophageal phase carried by peristalsis. The pharyngeal and esophageal phases are organised by a central pattern generator in the brainstem (the nucleus tractus solitarius and the surrounding reticular formation), which sequences motor output so that contraction and sphincter relaxation are correctly timed. Primary peristalsis is triggered by the swallow itself; secondary peristalsis is triggered by local distension and clears residual material. High-resolution manometry resolves the pressure topography of this wave and underlies the classification of normal and abnormal esophageal transport.

Clinical relevance

Normal transport is the reference against which disordered swallowing and esophageal motor disorders are recognised; when any phase fails, the result may be dysphagia, aspiration, or bolus retention. This entry describes the physiology for orientation and education and is not a guide to evaluating or treating an individual with swallowing difficulty.

History

Description of swallowing advanced from radiographic and electromyographic studies of the pharyngeal and esophageal phases to the synthesis of brainstem control around a central pattern generator, and, for the esophageal phase, from water-perfused manometry to high-resolution manometry, which made the topography of peristalsis directly visible and led to the Chicago Classification.

Key figures

• André Jean
• Peter J. Kahrilas
• John E. Pandolfino

Seminal works

• jean-2001-swallow
• kahrilas-2014-cc3

Frequently asked questions

What are the phases of swallowing?

Swallowing has a voluntary oral phase that prepares and pushes the bolus, an involuntary pharyngeal phase that protects the airway and opens the upper esophageal sphincter, and an esophageal phase carried by peristalsis into the stomach.

What is the difference between primary and secondary peristalsis?

Primary peristalsis is the contractile wave triggered by a swallow; secondary peristalsis is triggered locally by distension of the esophagus and serves to clear residual material that a swallow left behind.