VPB 121: Veterinary Physiology - II (2+1)

SWALLOWING REFLEX

• Swallowing centre is located in the brain stem (medulla oblongata)
• Stimulation of the receptors in the soft palate, pharynx (posterior wall) and epiglottis (dorsal surface) by food material initiate this reflex.
• It is a complex multi synaptic reflex involving pharyngeal and oesophageal stage.
• Sensory fibres pass through trigeminal, glossopharyngeal and vagus nerve.
• This reflex involves internuncial neurons.
• Efferent fibres emerge through glossopharyngeal, vagus and hypoglossal nerves which supply to the muscles of myohyoid and hypoglossal.
• The muscles press the tounge against hard palate.
• This causes the tounge to draw backward with the elevation of soft palate.
• Now the tounge forces the bolus into opened oesophagus.
• Opening of the oesophagus is by the pulling action of hyoid bone and layrnx.
• As it happens the epiglottis closes so as to shut the layrnx.
• Swallowing centre also activate through its efferent limb the neighbouring neurons that control respiration.
• This interupts respiration during swallowing as a preventive measure to avoid aspiration of food particles into respiratory passage.