Mastication and deglutition i

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

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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?

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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?

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Swallowing (Deglutition)

• Three stages;Voluntary Stage–Pharyngeal Stage (Involuntary)–Esophageal Stage (Involuntary)

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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.

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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?

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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

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