Anatomy and Physiology of swallowing Kwong Lee, Lee Fan, Felicity, Camilla, Sai Yan

Anatomy and Physiology of swallowing 3 stages:- Oral phase ( oral preparatory + oral transit ) Pharyngeal phase Oesophageal phase

Oral phase (1): oral preparatory phase Movement of the mandible (masseter, temporalis, lateral and medial pterygoid muscles) Formation of food into bolus Food held anterolaterally against the hard palate Process requires taste, temperature, touch and proprioreception senses

Oral phase (2): oral transit phase Manipulation of food bolus in central portion of tongue Sequential anterior to posterior tongue elevation Triggering pharyngeal reflex as bolus enters pharyngeal phase Voluntary phase controlled by the cerebral cortex (corticobulbar tract)

Pharyngeal phase Reflex < 1s Stimulation of swallowing receptor areas –tonsillar pillars  brain stem Closure of the nasal part of the pharynx Soft palate elevation – levator veli palatini Pulling forward of the posterior pharyngeal wall – superior constrictor muscle Contraction of the palatopharyngeal muscle

Pharyngeal phase (cont’d) Larynx pulled upward by contraction of stylopharyngeus, salpingopharyngeus, tyrohyoid and palatopharyngeus muscles Elevation of the larynx beneath the posteriorly bulging tongue displaces the epiglottis backwards – closure of the larynx

Pharyngeal phase (cont’d) Bolus moves downward over the epiglottis and reach lower part of the pharynx – contraction of superior, middle and inferior constrictor muscles Upward movement of larynx pulls up and enlarges the opening of the oesophagus Relaxation of UOS

Oesophageal phase Final phase Involuntary Peristaltic wave from UOS to LOS to stomach - 1° and 2° 1° - continuation of waves from pharynx, controlled by skeletal nerve impulses from IX and X nerve

Oesophageal phase (cont’d) 2° - inititated by myenteric nervous system and vagal afferent fibres  medulla vagal efferent Relaxation of LOS

In Summary