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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
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Movements of GITIngestion of food
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
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
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 Mahmood6
Functions of tongue1. Speech2. Taste3. Chewing4. Swallowing5. Lingual lipase6. Cleansing of teeth7. Moistening of lips
Ingestion of food
•Ingestion
•Mastication •Swallowing
Mastication (Chewing)•Teeth
•Anterior (Incisors) •Posterior (Molars)
•Cutting •Grinding
Muscles of mastication
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
Chewing Reflex• Components of reflex
1. Stimulus2. Receptors3. Afferent Nerve4. CNS5. Efferent Nerve6. Effector7. Response
• Components of Chewing reflex
1. Bolus of Food2. Receptors of Sensory
Nerves3. 5th Nerve4. Swallowing Centre5. 5th Nerve6. Muscles of Mastication7. Reflex Inhibition
→Rebound Contraction (Stretch Reflex)
Importance of Chewing
•Easy •passage •of food
•Prevent •excoriation
•of GIT
•↑Surface •area for
•Digestion
•Breaking•Of
•Indigestible•Membrane
•Chewing
Assessment Q. No.1 • How does the Chewing Reflex cause
Contraction of Muscles of Mastication?
© Prof. Dr. Rashid Mahmood 15
Ingestion of food
•Ingestion
Mastication •Swallowing
Swallowing (Deglutition)
• Pharynx (Respiration → Swallowing)
• Three stages;–Voluntary Stage–Pharyngeal Stage (Involuntary)–Esophageal Stage (Involuntary)
Voluntary Stage• Voluntarily Squeezed or
Rolled Posteriorly• Pressure of Tongue Upward
and backward• From here onward: Automatic
Voluntary Stage
Assessment Q. No.2 • What is direction of the tongue movement
during Voluntary Stage of Swallowing?
© Prof. Dr. Rashid Mahmood 20
Swallowing (Deglutition)
• Three stages;Voluntary Stage–Pharyngeal Stage (Involuntary)–Esophageal Stage (Involuntary)
22
Pharyngeal Stage (Involuntary)
•23Swallowing
Oropharyngeal stage of swallowing
Resting
Resting
Swallowing
Oropharyngeal stage of swallowing
Resting
Assessment Q. No.3 • Name the structure that moves upward
during pharyngeal stage of swallowing.
© Prof. Dr. Rashid Mahmood 27
Series of Automatic Pharyngeal Muscle Contractions
1. Soft Palate pulled upward↓
Posterior Nares Closed ↓
Prevents Reflux of food into Nasal Cavities
Series of Automatic Pharyngeal Muscle
Contractions2. Palatopharyngeal
folds pulled Medially ↓
Selective Slit
Series of Automatic Pharyngeal Muscle
Contractions3. 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
Series of Automatic Pharyngeal Muscle Contractions
4) Upward movement of Larynx ↓ Opening
of esophagus enlarged + Relaxation of Upper Esophageal Sphincter
↓ Easy
movement of food
Series of Automatic Pharyngeal Muscle
Contractions5. Muscular wall of Pharynx contracts
(Peristalsis)
Time taken by pharyngeal stage: < 6 seconds
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
Pharyngeal Stageswallowing reflex (Contd --------)
1. Stimulus→ Touch2. Receptors→ Tactile3. Afferent Nerve→ 5,94. CNS→ Swallowing Centre (Medulla &
Lower Pons)5. Efferent Nerve→ 5,9,10,126. Effector→ Muscles of Pharynx & Upper
esophagus7. Response → Contraction
Assessment Q. No.4 • What is swallowing reflex?
© Prof. Dr. Rashid Mahmood 35
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
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
© Prof. Dr. Rashid Mahmood 38