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Deglutition
Dr.A.P.Ganesan
Komarapalayam

Definition
Deglutition is a mechanical process by which the food bolus is tranported from the mouth to the stomach through pharynx and oesophagus

Deglutition occurs in 3 stages
The first stage occurs in the mouth, the second stage occurs in the pharynx and the third stage occurs in the oesophagus.
All these phases are reflex in nature and occur due to the stimulation of local  receptors present in the oral cavity and pharynx.
The presence of saliva also helps in the initiation of deglutition

First or Oral Stage
During this stage, the food passes from the mouth into the pharynx
By the act of mastication, the food is softened, lubricated and transformed into a bolus. The bolus is placed over the dorsal surface of the tongue. This is the preparatory position for the act of deglutition.
The front portion of  the tongue is retracted and depressed, the hyoid bone is elevated, the base of the tongue is elevated and retracted against the hard palate. By this movement, the food bolus is propelled into  the pharynx

Second or Pharyngeal Stage
During this stage, the food is passed from the pharynx into  the oesophagus.
In this phase, the food passes by downward and backward movement of the tongue, forward movementof the larynx and  contraction  of the superior constrictor muscles of the  pharynx called peristaltic movement .  By these actions the food bolus is passed from the pharynx into the oesophagus.
The oropharynx is in  communication with nasopharynx, oral  cavity, laryngeal  opening and oesophagus.
The entry  of food into the nasopharynx is prevented by the  elevation  of soft palate and  uvula against the posterior wall of pharynx.
The entry of food into oral  cavity is prevented by the elevation of the base of the  tongue against the  hard palate.
The entry of  food into  the  larynx is prevented by closing of larynx by epiglottis.
Since all other ways are closed, food finds its way into the oesophagus.
During this stage respiration and  speech are stopped.

Third of oespphageal stage
During this stage, the food bolus is passed from the  oesophagus into  the stomach.
Due to refles action, the upper oesophageal sphincter and lower cardiac sphincters are opened. The peristaltic movements arising from  the  pharynx continue into  the oesophagus sweeping the bolus downward into the stomach.

Deglutition center
Is situated in the floor of the fourth ventricle in the medulla

Afferent Nerves
Are trigeminal, glossopharyngeal and  vagus

Effernt Nerves
Trigeminal, facial and hypoglossal

Deglutition Animation





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