Esophagus Physiology

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ESOPHAGUS PHYSIOLOGY

NEET SS Surgery — High-Yield Revision Notes
3 Phases of swallowing
UES Upper sphincter
LES Lower sphincter
Peristalsis Bolus propulsion
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Quick Revision — MUST KNOW

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  • Primary function of the esophagus is transport of swallowed material from pharynx to stomach.
  • Swallowing consists of oral, pharyngeal and esophageal phases.
  • The upper esophageal sphincter prevents inappropriate entry of air into the esophagus and reflux into the pharynx.
  • The lower esophageal sphincter provides the major physiological barrier against gastroesophageal reflux.
  • Esophageal transport is primarily mediated by peristaltic contractions.
  • Primary peristalsis follows swallowing.
  • Secondary peristalsis clears residual material without a new swallow.
  • Tertiary contractions are generally non-propulsive.
NEET SS Pearl: Primary peristalsis is initiated by swallowing; secondary peristalsis is triggered by esophageal distension.
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Phases of Swallowing

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Phase Major feature Control
Oral Bolus preparation and propulsion Voluntary
Pharyngeal Rapid transfer through pharynx with airway protection Predominantly involuntary
Esophageal Peristaltic transport to stomach Involuntary
Exam Point: The esophageal phase transports the bolus from the upper esophageal sphincter toward the stomach.
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Upper Esophageal Sphincter

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  • Located at the pharyngoesophageal junction.
  • Main muscular component is the cricopharyngeus.
  • Normally remains tonically contracted.
  • Relaxes during swallowing to permit bolus entry into the esophagus.
  • Helps prevent air entry into the esophagus during respiration.
  • Dysfunction is associated with disorders such as Zenker diverticulum.
4

Primary Peristalsis

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  • Begins after initiation of a swallow.
  • Propagates down the esophagus toward the stomach.
  • Coordinates relaxation ahead of the bolus with contraction behind it.
  • Vagal pathways are important in coordinating esophageal peristalsis.
NEET SS Pearl: A normal swallow produces a coordinated peristaltic wave rather than simultaneous contraction throughout the esophagus.
5

Secondary & Tertiary Contractions

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Contraction Trigger Function
Primary Swallow Bolus propulsion
Secondary Esophageal distension Clear residual bolus
Tertiary Not normally coordinated with swallowing Non-propulsive
Remember: Secondary peristalsis is important for clearing retained food or refluxed material from the esophagus.
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Lower Esophageal Sphincter

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  • Provides the major physiological barrier to gastroesophageal reflux.
  • Has tonic basal pressure at rest.
  • Relaxes during swallowing to permit gastric entry.
  • Transient LES relaxations are an important mechanism underlying episodes of GER.
  • LES function is supported by the crural diaphragm.
Important: The LES is primarily a physiological high-pressure zone rather than simply an anatomical circular sphincter.
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Swallowing & LES Relaxation

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  • Swallowing initiates coordinated LES relaxation.
  • This allows the bolus to enter the stomach.
  • In achalasia, LES relaxation is impaired and esophageal body peristalsis is abnormal or absent.
Classic NEET SS Association: Achalasia = impaired LES relaxation + absent/disordered esophageal peristalsis.
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Neural Control

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Central Control

  • Swallowing is coordinated through brainstem swallowing centres.
  • Vagal pathways carry important motor signals.

Enteric Control

  • Myenteric plexus coordinates esophageal motor activity.
  • Excitatory and inhibitory pathways coordinate contraction and relaxation.
Key Concept: Normal peristalsis requires coordinated contraction behind the bolus and relaxation ahead of it.
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Esophageal Motility Disorders

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Disorder High-Yield Physiological Abnormality
Achalasia Impaired LES relaxation + absent/disordered peristalsis
Diffuse esophageal spasm Premature/uncoordinated contractions with intermittent normal peristalsis
Hypercontractile esophagus Excessively vigorous contractions
GERD Incompetent antireflux barrier and/or transient LES relaxations
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Important Concepts for Manometry

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  • LES resting pressure reflects the antireflux barrier.
  • Swallowing should produce appropriate LES relaxation.
  • Normal esophageal body contractions are sequential and coordinated.
  • Manometry evaluates contraction amplitude, timing and coordination.
  • High-resolution manometry is central to classification of esophageal motility disorders.
NEET SS Pearl: When interpreting an esophageal motility disorder, always assess: LES relaxation + peristalsis + contraction pattern.
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Clinical Correlations

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  • Dysphagia: may result from mechanical obstruction or impaired motility.
  • Achalasia: failure of LES relaxation with loss of normal peristalsis.
  • GERD: failure of the antireflux barrier allows gastric contents to enter the esophagus.
  • Diffuse spasm: abnormal timing and coordination of contractions.
  • Zenker diverticulum: associated with dysfunction at the upper esophageal sphincter.
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NEET SS — Facts You Should Never Miss

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  • Swallowing has oral, pharyngeal and esophageal phases.
  • Primary peristalsis follows a swallow.
  • Secondary peristalsis is triggered by esophageal distension.
  • Tertiary contractions are generally non-propulsive.
  • UES is predominantly related to the cricopharyngeus.
  • LES is a physiological high-pressure zone.
  • Normal swallowing requires LES relaxation.
  • Achalasia = impaired LES relaxation + absent/disordered peristalsis.
  • Normal peristalsis requires contraction behind + relaxation ahead of the bolus.
  • Manometry assesses LES relaxation and esophageal body motility.

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