Gastrointestinal Nursing.pdf

The Oesophagus 25geal nerves to the brain stem swallowing centre. Each impulse serves as atrigger for the swallowing reflex. This causes the elevation of the soft palate,which seals the nasal cavity and prevents food entering it. The swallowingcentre inhibits respiration by raising the larynx and closing the glottis to preventfood entering the trachea. The upper oesophageal sphincter, which is closedat rest, opens during swallowing to allow the bolus of food to pass into theoesophagus. Immediately after the bolus has passed, the sphincter closes again,resealing the junction. The pharyngeal phase of swallowing lasts approximatelyone second (Figure 3.1).Oesophageal phaseAs the peristaltic waves commence in the oesophagus, the muscle of the loweroesophageal sphincter relaxes, opening the sphincter and allowing the foodbolus to enter the stomach. The lower oesophageal sphincter muscle thencontracts to reseal the junction. The lower oesophageal sphincter remains closedin the absence of peristalsis, preventing the reflux of the acidic contents of thestomach into the oesophagus (Figure 3.2).Figure 3.1 Pharyngeal phase of swallowing. Reproduced by permission of HodderArnold from Clancy and McVicar (2002).Figure 3.2 Oesophageal phase of swallowing. Reproduced by permission of HodderArnold from Clancy and McVicar (2002).