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

DEGLUTITION (Swallowing)

• Deglutition is the act of passage of food from the mouth to the stomach through pharynx and oesophagus. It starts, as a voluntary act then becomes an involuntary reflex during its execution. The afferent nerves originate from receptors located in the posterior part of the mouth and pharynx. Deglutition center is situated in the medulla.
  • It is the motor activity involving the integrated movement of muscles of tongue, pharynx and oesophagus. (including the peristaltic movement)
  • It is under direct neural control of brain.
  • Complex action of tongue, to place the bolus centrally between the tongue and the hard palate. Pressure of the bolus in the pharynx stimulates pharyngeal pressure receptors to intiate swallowing reflex.

Act of swallowing

• It takes place in three phases
  • From mouth to pharynx (voluntary act)
  • From pharynx into the oesophagus (reflex mechanism)
  • From the oesophagus into the stomach (reflex mechanism)
• Contraction of mylohyoid and hypoglossal muscles.
• Pressing of the tongue against the hard palate and pulling the root of the tongue backwards.
• The tongue acts like a plunger driving bolus towards pharynx.
• Elevated soft palate is  to cut off communication with nasal passage.
• Forward pulling of hyoid bone and the larynx,cause opening of the entrance of oesophagus.
• Closure of the larynx by epiglottis make the bolus to enter directly into the oesophagus.