Oesophageal physiology

Physiology of Swallowing

• Peristaltic ring contraction – 4cm/s – if upright food & fluid generally falls before the wave
• The swallow is divided into three phases – oral, pharyngeal and oesophageal: 6 events in oropharyngeal phase occur rapidly – once initated rest is reflexive
• Oral
  • tongue moves bolus into posteior oropharynx
  • tounge moves posteriorly and thrusts bolus into hypopharynx
• Pharyngeal
  • Soft palate elevated to close passage into nasopharynx
  • Hyoid bone anterior and elevated to bring epiglottis under tounge
  • Hyoid moving elevates larynx and opens retrolaryngeal space
  • Epiglottis tilts back to cover larynx
• Oesophageal phase
  • Initiated by oropharyngeal phase
  • UOS relaxes and inf constrictor pushes bolus into upper oesophagus
  • UOS then contracts to reach 90mmHg to prevent reflux
  • Primary peristalsis = wave associated with swallowing, beginning at UOS
    • Speed of peristalsis 2-5 cm/s
    • Waves of at least 40-80mmHg
  • Secondary peristalsis = stimulated by oesophageal distension; independent of oral events
  • Tertiary peristalsis = abnormal waves - nonprogressive.
    • Uncoordinated contractions that can progress to oesophageal spasm.
    • These may be seen in elderly with no disease

Physiology of LOS

• Lower Oesophageal sphincter
• Not a ‘true’ sphincter but a high pressure zone across 2-5cm usually ‘closed’ in the resting state;
• normal: 12-20mmHg pressure.
• At least 1cm is intraabdominal.
• Peristaltic waves are not strong enough to ‘open’ LES
• Requires vagal mediated relaxation of LES
  • Occurs 1.5 s after swollowing and lasts 4-5 seconds.