The document summarizes the physiology of deglutition (swallowing) in three stages: 1) oral stage where food is prepared in the mouth and propelled to the oropharynx, 2) pharyngeal stage where the nasopharyngeal and oropharyngeal isthmuses close and the larynx elevates to prevent aspiration as the food bolus is pushed down, and 3) esophageal stage where peristalsis propels the bolus through the esophagus and into the stomach. Key events in each stage include tongue movement, closure of the larynx, contraction of the pharyngeal constrictor muscles, and opening/closing of the cricopharyngeal sphinct

1. Physiology of
Deglutition
Dr. Vishal Sharma

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

3. 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

4. Oral preparatory stage

5. 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

6. Oral propulsive stage

7. 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)

8. 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 (?)

9. Nasopharyngeal isthmus closed

10. Elevation & closure of Larynx

11. Oropharyngeal isthmus closed

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

13. Tongue driving force

14. Contraction & elevation of
pharynx

15. Opening of cricopharynx

16. 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

17. Closing of cricopharynx

18. Opening & descent of larynx

19. Oesophageal Peristalsis

22. Peristalsis

23. Intraluminal pressure changes

24. Bolus enters stomach

25. 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

26. Recap

27. Oral preparatory stage

28. Oral propulsive stage

29. Nasopharyngeal isthmus closed

30. Elevation & closure of Larynx

31. Oropharyngeal isthmus closed

32. Tongue driving force

33. Contraction & elevation of
pharynx

34. Opening of cricopharynx

35. Closing of cricopharynx

36. Opening & descent of larynx

37. Primary Peristalsis

38. Bolus enters stomach

39. Video-fluoroscopy
Lateral view

40. Oral propulsive stage

41. Larynx elevation

42. Closure of nasopharyngeal isthmus & larynx

43. Contraction of upper constrictor

44. Contraction of middle constrictor

45. Contraction of lower constrictor & relaxation of
cricopharyngeal sphincter

46. Cricopharyngeal sphincter closes & larynx opens

47. Video-fluoroscopy
Anterior view

48. Contrast enters oropharynx

49. Pyriform fossae fill symmetrically

50. Contrast reaches crico-pharyngeal sphincter

51. Cricopharynx opens & contrast enters esophagus

52. Constrictors squeeze all contrast into esophagus

53. No stasis

54. 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)

56. 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

58. Thank You