Physiology of Deglutition Dr. Vishal Sharma

Stages Oral stage (lasts for 1 second, voluntary) Preparatory phase Propulsive phase Pharyngeal Stage (1 second, involuntary) Oesophageal Stage (8-20 seconds)

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

Oral preparatory stage

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

Oral propulsive stage

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)

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 (?)

Nasopharyngeal isthmus closed

Elevation & closure of Larynx

Oropharyngeal isthmus closed

Pharyngeal stage 5. Posterior retraction of base tongue: tongue driving force 6. Pharyngeal constrictors contract 7. Elevation of pharynx 8. Opening of cricopharyngeal sphincter

Tongue driving force

Contraction & elevation of pharynx

Opening of cricopharynx

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

Closing of cricopharynx

Opening & descent of larynx

Oesophageal Peristalsis

Peristalsis

Intraluminal pressure changes

Bolus enters stomach

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

Recap

Oral preparatory stage

Oral propulsive stage

Nasopharyngeal isthmus closed

Elevation & closure of Larynx

Oropharyngeal isthmus closed

Tongue driving force

Contraction & elevation of pharynx

Opening of cricopharynx

Closing of cricopharynx

Opening & descent of larynx

Primary Peristalsis

Bolus enters stomach

Video-fluoroscopy Lateral view

Oral propulsive stage

Larynx elevation

Closure of nasopharyngeal isthmus & larynx

Contraction of upper constrictor

Contraction of middle constrictor

Contraction of lower constrictor & relaxation of cricopharyngeal sphincter

Cricopharyngeal sphincter closes & larynx opens

Video-fluoroscopy Anterior view

Contrast enters oropharynx

Pyriform fossae fill symmetrically

Contrast reaches crico-pharyngeal sphincter

Cricopharynx opens & contrast enters esophagus

Constrictors squeeze all contrast into esophagus

No stasis

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)

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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