pd

1. Physiology of
Deglutition
Dr. Krishna
Koirala
2016-12-05

2. • Mechanism which transmits liquids or
solids from the mouth to the stomach via
the pharynx and esophagus without
entering the respiratory tract
• During swallowing, muscles are activated
in an orderly sequence
– Controlled by complex neuromuscular
interaction
– Triggered by volitional cortical drive or

3. • Neural networks that are
responsible for this automatic
swallowing process are called
central pattern generator
• Sites
– Brainstem, nucleus tractus solitarius ,
nucleus ambiguus, reticular formation

5. Stages
1. Oral stage (lasts for 1 second,
voluntary)
–Preparatory phase
–Propulsive phase
1. Pharyngeal Stage (1 second,

6. Oral preparatory
stage
• Processing of the bolus to render it
swallowable
• Solid food chewed, lubricated with saliva
& converted to a bolus
• Requires coordinated movement of lips,
cheeks, jaws and tongue against a closed

7. Nerves involved : V , VII, X, XII
Liquid - about 1 second, Solids - 5-

8. Oral propulsive stage
• Propelling of food from the oral cavity
into the oropharynx
• Bolus propelled backwards by pressing of
tongue against hard palate.
Approximation of tongue against hard
palate starts with tip of tongue and
moves back
• Ends when food bolus crosses anterior

9. Oral propulsive stage

10. Pharyngeal stage
1. Nasopharyngeal isthmus closed:
soft palate touches Passavant’s
ridge
2. Elevation of larynx → negative
pressure in hypopharyngeal lumen
(suction pump)
3. Oropharyngeal isthmus closed:

12. 4. Closure of larynx: (Laryngeal Tier
Mechanism)
• Below upwards
– True vocal cords approximate
– False cords approximate
– Aryepiglottic folds approximate
• Temporary cessation of respiration
• Epiglottis falls back over laryngeal inlet

13. Nasopharyngeal isthmus
closed

14. Elevation & closure of Larynx

15. Oropharyngeal isthmus
closed

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

17. Opening of cricopharynx

18. Esophageal stage
1. Closure of cricopharyngeal sphincter
2. Opening and descent of larynx
3. Primary peristalsis
– Large amplitude, propulsive, 8-9 seconds
4. Secondary peristalsis : arise locally in
response to distension
– Small amplitude, propulsive, for food
remnants
5. Tertiary Esophageal contractions

19. Closure of
cricopharynx
Opening & descent of
larynx

20. Esophageal Peristalsis

21. Bolus enters stomach

22. Neural Mechanism
• Afferents : V, IX & X cranial nerves
• Deglutition centre: Medulla oblongata
• Efferents
– X, XI & XII cranial nerves → tongue,
pharynx, larynx and esophageal
muscles
• Cessation of respiration
– Connection between deglutition and

23. • CN V : Chewing
• CN VII : Sensation to oropharynx & taste
to anterior 2/3 of tongue
• CN IX : Taste to posterior 1/3rd
of
tongue, sensory and motor
functions of the pharynx
• CN X : Taste to oropharynx, sensation
and motor function to larynx and
laryngopharynx . Airway

24. Factors preventing reflux
• Anatomical
– Lower esophageal sphincter
contraction
– Pinch cock action of right crus of
diaphragm
– Lower esophageal mucosal folds
(valvular)
– Oblique esophageal entry into
stomach

25. • Physiological
– Unidirectional esophageal
peristalsis
– Gastric emptying