MASTICATION & DEGLUTITION
Dr.Remya.K.J MBBS, MD.,
Professor
Department of Physiology
SSSMC&RI
Specific Learning Objectives
• Explain the process of mastication
• Outline the process of Deglutition.
• Achalasia Cardia
Mastication
• First mechanical
activity to which
food is subjected in
the mouth.
• Food is broken
down into particles.
• Partly voluntary &
partly reflex
mechanism
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Mastication reflex
Food in mouth exerts pressure against gums,teeth & hard palate
This stimulates receptors & generates afferent impulses
Impulses cause (-) of jaw closing muscles &
contraction of jaw opening muscles
During opening of the jaw,closing muscles are stretched
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Mastication reflex
Activation of muscle spindles causes reflex contraction
Jaw closes
This continues reflexly till food is broken down
into small particles
• Buccinator prevents accumulation of food b/w
cheek & the gums.
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Deglutition
• Process by which chewed food is emptied from the
mouth into stomach.
• Divided into 3 stages:
1.Oral phase
2.Phrayngeal phase
3.Oesophageal phase
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1.Oral phase
Bolus formed is projected to the back of tongue
Tongue is elevated & pressed against hard palate
Soft palate is elevated
Bolus is propelled into pharynx
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Buccal phase
the tongue presses
against the hard
palate, forcing the food
bolus into the
oropharynx
where the involuntary
phase begins.
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Nervous control of Oral phase
• Voluntary stage
• Mylohyoid, styloglossus & intrinsic tongue muscles
help.
• impulses from cortex CN V & XII Mylohyoid,
styloglossus & intrinsic tongue muscles
movements propulsion of bolus pharyngeal
stage initiated.
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2.Pharyngeal phase
• Reflex process
(deglutition
reflex)
• Once initiated,
proceeds without
interruption –
swallowing reflex
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Swallowing reflex
Sensory receptors near ant & post pillars
Sensory receptors near ant & post pillars of fauces & tonsils
of fauces & tonsils
Sensory Impulses(afferents) carried
S.Impulses carried by CN V & IX to centre in reticularby CN V & IX
formation
to centre in reticular formation
Motor impulses from centre by CN V, IX, X, XII
Motor impulses from centre by CN V, IX, X, XII
• Centre inhibits respiration, sneezing, coughing &
vomiting
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Swallowing
• Food can enter into
any 4 of the
passages.
• Food is propelled
into esophagus by
integrated action of
swallowing centre.
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Mechanism of swallowing
1. Soft palate is pulled upwards – prevents aspiration
into nasal cavity.
2. Vocal cords approximated
3. Epiglottis swings backwards
4. Larynx pulled upwards
(All the mechanism prevents passage of food into
trachea.)
5. Respiration arrested – Deglutition apnea
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Mechanism of swallowing
6. Persistent elevation of tongue maintains high pressure
gradient – prevents reentry of food into mouth.
7. Upward movement of larynx stretches opening of
esophagus.
-upper esophageal sphincter relaxes
-peristaltic wave (primary) move downward into
esophagus
-this results in propulsion of food.
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3.Oesophageal phase
• Bolus is pushed from
pharynx to the
esophagus.
• Esophagus shows 3 types
of Peristaltic waves
• They are: primary,
secondary & tertiary.
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Peristaltic waves
• Primary - starts
from pharynx
- propels food
through
oesophagus
- controlled by
vagus through
myentric plexus
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Peristaltic waves
• Secondary wave – if
bolus not emptied by
primary, distension of
esophagus initiates
secondary.
Helps in emptying of food
into stomach.
• Tertiary wave – occurs
irregularly & locally in
esophagus.
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The gastro-esophageal
sphincter opens, and food
enters the stomach
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Applied Physiology
1. Achalasia cardia
2. Reflex esophagitis
3. Dysphagia
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Achalasia
• During
swallowing the
LOS fails to relax
& remains in a
tonically
contracted state.
• As a result food is
not emptied into
the stomach.
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Achalasia - Causes
1. Degeneration of the myenteric plexus in lower part of
esophagus.
2. Increased sensitivity of LOS to gastrin
3. Inadequate release of (-) neurotransmitter VIP & NO
• Peristaltic wave can’t be conducted---food stasis
• Esophagus gets dilated – Mega esophagus
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Achalasia - Treatment
• Antispasmodic drugs –
relaxation of LOS.
• Botulinum toxin
injected locally to
inhibit the release of
Ach.
• Surgical – Heller’s
Myotomy done to open
LOS.
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Reflex esophagitis
• Heartburn
• Due to
reflux of
gastric
contents
into the
esophagus.
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Reflex esophagitis
• Causes:
1.Due to failure of closure of LOS
2.Hiatus hernia
• Clinical features: heart burn, chest pain, lump in
throat.
• Complications – strictures, ulcers, adenocarcinoma of
esophagus.
• Treatment – antacids, H2 blockers, proton pump
inhibitors
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