There are 4 phases of swallowing:
1. The Pre-oral Phase
– Starts with the anticipation of food being introduced into the mouth – Salivation is triggered by the sight and smell of food (as well as hunger)
2. The Oral Phase
– The lips close and form a seal – Chewing / mastication of food begins – The food is mixed with saliva to form a bolus – The bolus is then transferred to the back of the mouth
3. The Pharyngeal Phase
– Reflexive (reflex response- i.e. not planned) initiation of the swallow. – The nasal cavity is sealed when the soft palate raises (that prevents food/fluid coming out of the nose) – The larynx (voice box) moves upwards and forward – The vocal folds close, and then the epiglottis closes over the airway (breathing stops momentarily) – The pharynx pushes the bolus down (by contracting in a stripping motion) – The upper oesophageal sphincter opens to allow the bolus through – The upper oesophageal sphincter closes after the bolus has passed through in order to prevent the bolus moving back up (retrograde movement)
4. The Oesophageal Phase
– The bolus is transported through the oesophagus by wavelike muscular contractions (peristalsis) into the stomach – The lower oesophageal sphincter opens to allow the bolus into the stomach – The lower oesophageal sphincter closes after the bolus has passed through (to prevent reflux / regurgitation)