O1ii: Explain the factors that prevent gastro-oesophageal reflux


Gastro-oesophageal Reflux = backward flow of the contents of stomach into the oesophagus that is due to malfunctioning of the Lower Oesophageal Sphincter

Factors that Maintain Les Integrity

  • LES is formed by the lowest 2 – 4cm of the oesophagus → acts as a physiologic sphincter by tonic contraction of muscle fibres
    1. Anatomical
    2. Pressure
    3. Hormones
    4. Physiology

1) Anatomical

  • Intrinsic Sphincter
    • Smooth m. of the oesophagus
    • Neural control (Vagus n.)
      • ACh – sphinter contracts
      • NO, VIP-sphincter relaxation (just after swallowing) 
  • Extrinsic sphincter
    • Skeletal m. fibres of diaphragm
    • Neural control (Phrenic n.)
      • Actions coordinated with resp
    • Fibres surround oesophagus & exert ‘pinchcock-like” action
  • Gastro-oesophageal angle
    • Oblique “sling” fibres of stomach
    • Creates a flap valve to help close off gastro-oesophageal junction when ↑intra-gastric P

2) Pressure

    • At rest, LOS pressure is 15 – 25mmHg greater than gastric P
    • Prevents G-O reflux

3) Hormones

  • ↑TONE: gastrin, motilin, α-adrenergic stimulation
  • ↓TONE: glucagon, VIP, progesterone

4) Physiology

    • 1 – 2 secs after swallowing LES relaxes
    • Remains relaxed for ~10 secs then contracts
    • After passage of food bolus, LES tone rises ~10mmHg above resting tone for 15 secs, before returning to resting level

5) Drugs

  • ↑LES: metoclopramide, anticholinesterases, α-adrenergic agonists, histamine, suxamethonium
  • ↓LES: antimuscarinics (atropine), dopamine, ethanol, opioids, β-adrenergic agents


  • Intraluminal manometry
  • Continuously infused catheter probes are withdrawn from the stomach in small increments
  • Pressure being measured the whole time