this lecture relates to physiology of ingestion of food, and includes mastication (chewing) and deglutition (swallowing)

1. Mastication and Deglutition-I
•Swallowing becomes a great concern for the elderly, mainly due
to strokes and Alzheimer's disease.
•It has been reported that 25%-45% of typically developing
children demonstrate feeding and swallowing problems
•Prevalence is estimated to be 30%-80% for children with
developmental disorders
•Each year, approximately one in 25 adults will experience a
swallowing problem in the United States
•Swallowing problems are more common among older
individuals
•A patient with dysphagia is unable to consume sufficient
calories and nutrients to maintain health.
Prof. Dr. Rashid Mahmood

2. 2
Movements of GIT
Ingestion of food

4. 4
Hunger & Appetite
• The amount of food
that a person
ingests is
determined
principally by
intrinsic desire for
food is called
hunger
• The type of food
that a person
preferentially seeks
is determined by
appetite

5. Objectives
• Specific Objectives: At the end of the lesson student will be
able to:
• List the Functions of tongue
• Define Mastication and describe Importance of Chewing
• Describe the components of Chewing Reflex
• Name the Stages of Swallowing (Deglutition)
• Describe the events occurring in Voluntary Stage of
swallowing
• Outline the Series of Automatic Pharyngeal Muscle
Contractions occurring in Pharyngeal Stage of swallowing
• Describe swallowing reflex
Goal/Aim: To give the understanding of the
physiology of Mastication and Deglutition

6. Lesson Contents
• Functions of tongue
• Mastication (Chewing)
– Control (Nerve Supply) of Muscles of Chewing
– Chewing Reflex
– Importance of Chewing
• Swallowing (Deglutition)
– Voluntary Stage
– Pharyngeal Stage (Involuntary)
• Series of Automatic Pharyngeal Muscle Contractions
– swallowing reflex
© Prof. Dr. Rashid Mahmood
6

7. Functions of tongue
1. Speech
2. Taste
3. Chewing
4. Swallowing
5. Lingual lipase
6. Cleansing of teeth
7. Moistening of lips

8. Ingestion of food
•Ingestion
•Mastication •Swallowing

9. Mastication (Chewing)
•Teeth
•Anterior (Incisors) •Posterior (Molars)
•Cutting •Grinding

11. Muscles of mastication

12. Control (Nerve Supply) of Muscles of Chewing
• Motor Branch of 5th
Cranial Nerve
Specific reticular areas in brain
Stem taste Centers
• Nucleus of Tractus Solitarius, and
nucleus ambiguus
• Hypothalamus
• Amygdala
• Cerebral Cortex

13. Chewing Reflex
• Components of reflex
1. Stimulus
2. Receptors
3. Afferent Nerve
4. CNS
5. Efferent Nerve
6. Effector
7. Response
• Components of
Chewing reflex
1. Bolus of Food
2. Receptors of Sensory
Nerves
3. 5th
Nerve
4. Swallowing Centre
5. 5th
Nerve
6. Muscles of Mastication
7. Reflex Inhibition
→Rebound Contraction
(Stretch Reflex)

14. Importance of Chewing
•Easy
•passage
•of food
•Prevent
•excoriation
•of GIT
•↑Surface
•area for
•Digestion
•Breaking
•Of
•Indigestible
•Membrane
•Chewing

15. Assessment Q. No.1
• How does the Chewing Reflex cause
Contraction of Muscles of Mastication?
© Prof. Dr. Rashid Mahmood 15

16. Ingestion of food
•Ingestion
Mastication •Swallowing

17. Swallowing (Deglutition)
• Pharynx (Respiration →
Swallowing)
• Three stages;
–Voluntary Stage
–Pharyngeal Stage (Involuntary)
–Esophageal Stage (Involuntary)

18. Voluntary Stage
• Voluntarily Squeezed or
Rolled Posteriorly
• Pressure of Tongue Upward
and backward
• From here onward:
Automatic

19. Voluntary
Stage

20. Assessment Q. No.2
• What is direction of the tongue movement
during Voluntary Stage of Swallowing?
© Prof. Dr. Rashid Mahmood 20

21. Swallowing (Deglutition)
• Three stages;
Voluntary Stage
–Pharyngeal Stage (Involuntary)
–Esophageal Stage (Involuntary)

22. 22
Pharyngeal Stage (Involuntary)

23. •23Swallowing
Oropharyngeal stage of swallowing
Resting

24. Resting

25. Swallowing
Oropharyngeal stage of swallowing
Resting

27. Assessment Q. No.3
• Name the structure that moves upward
during pharyngeal stage of swallowing.
© Prof. Dr. Rashid Mahmood 27

28. Series of Automatic Pharyngeal
Muscle Contractions
1. Soft Palate pulled upward
↓
Posterior Nares Closed
↓
Prevents Reflux of food into
Nasal Cavities

29. Series of Automatic
Pharyngeal Muscle
Contractions
2. Palatopharyngeal
folds pulled Medially
↓
Selective Slit

30. Series of Automatic Pharyngeal
Muscle Contractions
3. Vocal Cords strongly approximated
+
Larynx pulled upward & anteriorly
+
(Ligaments prevent upward movement of Glottis)
↓
Epiglottis swings backward over opening of Larynx
↓
Prevent Passage of into Trachea

31. Series of Automatic Pharyngeal
Muscle Contractions
4) Upward movement of Larynx
↓
Opening of esophagus enlarged
+ Relaxation
of Upper Esophageal Sphincter
↓
Easy
movement of food

32. Series of Automatic
Pharyngeal Muscle
Contractions
5. Muscular wall of Pharynx contracts
(Peristalsis)
Time taken by pharyngeal stage:
< 6 seconds

33. Pharyngeal Stage (Contd --------)
• Nervous Initiation (Reflex)
–Most sensitive tactile area:
• Ring around pharyngeal opening;
Greatest sensitivity on Tonsillar Pillars
–Effect on Respiration:
• Swallowing centre inhibits Respiratory
centre of Medulla

34. Pharyngeal Stage
swallowing reflex(Contd --------)
1. Stimulus→ Touch
2. Receptors→ Tactile
3. Afferent Nerve→ 5,9
4. CNS→ Swallowing Centre (Medulla
& Lower Pons)
5. Efferent Nerve→ 5,9,10,12
6. Effector→ Muscles of Pharynx &
Upper esophagus
7. Response → Contraction

35. Assessment Q. No.4
• What is swallowing reflex?
© Prof. Dr. Rashid Mahmood 35

36. Summary
• Ingestion of food involves two processes: Mastication
(Chewing) & Swallowing (Deglutition)
• Teeth cut & grind the bolus of food
• Mastication is brought about by Muscles of Chewing,
Controlled mainly by 5th Nerve.
• Chewing Reflex, initiated by bolus of food in mouth results in
reflex inhibition of Muscles of Mastication. This results in
Stretch Reflex, causing their Rebound Contraction
• Swallowing (Deglutition) occurs in three stages: Voluntary
Stage, Pharyngeal Stage and Esophageal Stage
• Voluntary Stage involves mainly tongue, pushing the bolus of
food in pharynx
• Pharyngeal Stage is Involuntary; in this stage swallowing
reflex results in Series of Automatic Pharyngeal Muscle
Contractions

37. Learning resources
• Guyton and Hall (Text book of physiology),
13th
edition, P.708-709
• Ganong (Text book of physiology), 24th
Edition, P. 500-501
• Walter F. Boron Medical Physiology, 2nd
Edition, P.890-891
© Prof. Dr. Rashid Mahmood 37

38. © Prof. Dr. Rashid Mahmood 38