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Physiology of Deglutition
Dr. Vishal Sharma
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Stages Oral stage (lasts for 1 second, voluntary) Preparatory phase
Propulsive phase Pharyngeal Stage (1 second, involuntary) Oesophageal Stage (8-20 seconds)
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Oral preparatory stage
Not required for liquids Solid food chewed, lubricated with saliva & converted to a bolus Requires coordinated movement of lips, cheeks, jaws & tongue against a closed oropharyngeal isthmus
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Oral preparatory stage
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Oral propulsive stage Food bolus propelled backwards by pressing of tongue against hard palate Approximation of tongue against hard palate starts with tip of tongue & moves back Stage ends when food bolus crosses anterior tonsillar pillar
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Oral propulsive stage
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Pharyngeal stage 1. Nasopharyngeal isthmus closed: soft palate touches Passavant’s ridge 2. Oropharyngeal isthmus closed: tongue base touches palate 3. Elevation of larynx: negative pressure in hypopharyngeal lumen (suction pump)
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Pharyngeal stage 4. Closure of larynx: below upwards
True vocal cords approximate False cords approximate Ary-epiglottic folds approximate Temporary cessation of respiration Epiglottis falls back over larynx inlet (?)
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Nasopharyngeal isthmus closed
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Elevation & closure of Larynx
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Oropharyngeal isthmus closed
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Pharyngeal stage 5. Posterior retraction of base tongue: tongue driving force 6. Pharyngeal constrictors contract 7. Elevation of pharynx 8. Opening of cricopharyngeal sphincter
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Tongue driving force
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Contraction & elevation of pharynx
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Opening of cricopharynx
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Oesophageal stage 1. Closing of cricopharyngeal sphincter
2. Opening & descent of larynx 3. Primary peristalsis: large amplitude, propulsive 4. Secondary peristalsis: small amplitude, propulsive, for food remnants 5. Relaxation of lower esophageal sphincter: food bolus enters stomach
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Closing of cricopharynx
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Opening & descent of larynx
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Oesophageal Peristalsis
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Peristalsis
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Intraluminal pressure changes
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Bolus enters stomach
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Neural Mechanism Afferent: 5th, 9th & 10th cranial nerves
Deglutition centre: medulla oblongata Efferent: 10th, 11th & 12th cranial nerves tongue, pharynx, larynx & oesophagus muscles Cessation of respiration: connection between deglutition & respiration centres in medulla
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Recap
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Oral preparatory stage
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Oral propulsive stage
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Nasopharyngeal isthmus closed
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Elevation & closure of Larynx
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Oropharyngeal isthmus closed
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Tongue driving force
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Contraction & elevation of pharynx
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Opening of cricopharynx
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Closing of cricopharynx
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Opening & descent of larynx
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Primary Peristalsis
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Bolus enters stomach
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Video-fluoroscopy Lateral view
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Oral propulsive stage
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Larynx elevation
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Closure of nasopharyngeal isthmus & larynx
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Contraction of upper constrictor
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Contraction of middle constrictor
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Contraction of lower constrictor & relaxation of cricopharyngeal sphincter
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Cricopharyngeal sphincter closes & larynx opens
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Video-fluoroscopy Anterior view
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Contrast enters oropharynx
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Pyriform fossae fill symmetrically
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Contrast reaches crico-pharyngeal sphincter
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Cricopharynx opens & contrast enters esophagus
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Constrictors squeeze all contrast into esophagus
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No stasis
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Factors preventing reflux
Anatomical: 1. Lower oesophageal sphincter contraction 2. Pinch cock action of right crus of diaphragm 3. Oblique esophageal entry into stomach 4. Lower esophageal mucosal folds (valvular)
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Factors preventing reflux
5. Oblique gastric muscle around lower esophagus 6. Abdominal pressure > gastric pressure & intra-thoracic pressure Physiological: 1. Unidirectional esophageal peristalsis 2. Gastric emptying
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Thank You
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