O1ii: Describe the mechanism of swallowing


Swallowing is the process by which food moves from oral cavity → stomach

  • Complex coordinated movements, initiated voluntarily & integrated by swallowing centre in Medulla

3 Phases

1) Oral Phase (Voluntary)

  • Food bolus is formed by tongue, chewing, enzymes & H2O (lingual lipase, salivary amylase)
  • Tongue propels bolus up + back against hard + soft palate
  • Stimulates glossopharyngeal (IX) receptors which activate the swallowing reflex → produces involuntary next two phases

2) Pharyngeal Phase (Involuntary) Via Vagal (X) Efferents

  • Respiration inhibited for 2 seconds
  • Nasopharynx closed by soft palate
  • Adduction of VCs (aryepiglottic muscles)
  • Larynx raised up
  • Epiglottis swings down to cover larynx
  • Bolus food pushed into oesophagus by pharynx contraction & opening of Upper Oesophageal Sphincter

3) Oesophageal Phase (Involuntary) Via Vagal (X) Efferents

  • Food enters oesophagus → upper oesophagus sphincter shuts & lower oesophageal sphincter relaxes
  • Slow peristaltic waves (via Vagus) are initiated
  • Food moves down (Gravity influences fluid > food)
  • Secondary peristaltic waves initiated by enteric NS promote further peristalsis → once food enters stomach, LES shuts