3. INTRODUCTION
Ingestion include 4
steps
Placing food in mouth
Mastication
Lubrication
Swallowing.
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4. MASTICATION
Chewing – food is cut &
grounded into smaller
pieces.
Achieved by
Movement of jaw
Action of teeth
Coordinated movements
of tongue & muscles of
oral cavity.
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6. Thursday, June 18, 2020
Food placed
in mouth
stretches jaw –
initiate stretch
reflex
contraction of
muscles of
mastication –
mouth closed
food comes in
contact with
buccal receptors –
inhibits
contraction & also
initiate
contraction of
Digastric & Lateral
Pterygoid muscles
open mouth
– cycle
continues
7. MUSCLES OF MASTICATION
Masseter – raises & protract
mandible & clenches teeth.
Temporalis – retract
mandible
Int & ext Pterygoids –
protrude & depress mandible
& opens mouth
Buccinator- prevents
accumulation of ffod between
teeth & cheek.
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8. FUNCTIONS OF MASTICATION
Breaking of food into smaller pieces.
Mixing of food with saliva
Swallowing & lubrication & softening of food
Stimulate olfactory receptors & taste
receptors & increase pleasure of eating &
stimulate gastric secretion.
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9. DEGLUTITION
Def – Passage of food from oral cavity to into
stomach.
Phases
Oral
Pharyngeal
Oesophageal
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10. ORAL
First stage
Voluntary
Bolus of food after
mastication put over
dorsum of tongue
Tongue forces back
into oropharynx
against hard palate.
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11. PHARYNGEAL
Second stage
Involuntary by
swallowing reflex
Receptors – around
opening of pharynx
over tonsillar pillars
Afferents – Trigeminal,
Glossopharyngeal &
Vagus nerve.
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12. PHARYNGEAL
Center – Deglutition center
– in medulla & lower pons
(in NTS & Nucleus
Ambiguus)
Efferent – through 5th, 9th,
10th & 12th
Effector organ –
pharyngeal musculature &
tongue (causes contraction)
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14. OESOPHAGEAL
Food pushed from upper
part of oesophagus to
stomach by oesophageal
peristalsis & helped by
greavity.
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15. APPLIED PHYSIOLOGY
Oesophagus –
fibromuscular tube
about 25 cm long
Seperated from pharynx
by UES (Upper
oesophageal sphincter
& stomach by LES
(Lower oesophageal
sphincter)
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16. OESOPHAGEAL PERISTALSIS
Primary – Initiated by swallowing &
coordinated by vagal fibers from swallowing
centers
As food enters oesophagus UES contracts prevents
regurgitation of food into mouth & propels food
down.
As reaches LES , it relaxes & allow food to enter
stomach.
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17. OESOPHAGEAL PERISTALSIS
Secondary – when primary peristalsis is not
able to pass food down, remaining food
stretches mechanical receptors & initiate
secondary peristalsis.
It is coordinated by intrinsic nervous system
of oesophagus.
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18. DISORDERS OF SWALLOWING
Abolition of deglutition
reflex – causes
regurgitation of food into
nose or aspiration into
larynx. Occurs in
IX & X nerve paralysis
When pharynx
anaesthetized with cocaine.
Aerophagia – unavoidable
swallowing of air.
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19. DISORDERS OF SWALLOWING
Dysphagia – Difficulty in swallowing.
Cardiac achalsia – neuromuscular disorder
of LES, failure of LES to relax & food
accumulate in lower oesophagus.
Gastroesophageal reflux disease.
Incompetence of LES, leads to reflux of acidic
gastric content into oesophagus.
Causes pain & irritation.
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20. Physiology of gastric motility
Gastric musculature
Three layers of smooth
muscle fibres:
Outer longitudinal layer,
Middle circular layer
Inner oblique layer.
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21. Physiology of gastric motility
As per gastric
contractions
Stomach shows 2
regions
Oral region
Caudal region.
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22. Motor functions of stomach
Done by the gastric motility are:
Storage of food,
Mixing of food and
Slow emptying of food.
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23. Initiation of gastric motility
Basal electrical rhythm.
Represents a wave of depolarization of
smooth muscle cells from the circular
muscles of the fundus of stomach
To the pyloric sphincter.
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24. Basal electrical rhythm.
Initiated by the
pacemaker cells located
near the fundus on the
greater curvature of the
stomach.
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25. Basal electrical rhythm.
Gastric slow waves
consist of an upstroke
and an plateau phase.
3–4 waves/min
upstroke is due to flow
of Na+ and Ca2+ into
the cell
Plateau is dependent on
the flow of Ca2+ into
the cell
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26. Factors affecting contractility
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Initiate contraction.
Gastrin,
Histamine,
Nicotine,
Barium and K+
Inhibit contraction.
Enterogastrone,
Epinephrine,
Norepinephrine,
Atropine and Ca2+.
27. Types of gastric motility.
Motility of empty stomach
Migrating motor complex
Hunger contractions
Gastric motility related to meal
Receptive relaxation
Mixing peristaltic waves
Gastric emptying.
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28. Motility of empty stomach
Migrating motor complex
Hunger contractions
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29. Migrating motor complex
Peristaltic wave that
begins in the oesophagus
and travels through the
entire gastrointestinal
tract (migratory motor
activity) during
interdigestive period
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31. Migrating motor complex
Rate -- regular rate (5
cm/min)
Frequency - every 60–
90 min during the
interdigestive period
Motilin
Food entry
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32. Hunger contractions
Mild peristaltic
contractions
MMC – responsible
When become strong
fuse to form tetanic
contraction lasting for
2–3 min
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33. Gastric motility related to
meal
Receptive relaxation
Mixing peristaltic waves
Gastric emptying.
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34. Receptive relaxation
Food stimulates the
stretch receptors of
oral region produces
relaxation
vagovagal reflex
Cholecystokinin, VIP
or NO
Vagotomy abolishes
receptive relaxation
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35. Mixing peristaltic waves
Food in the caudal region
(distal body and antral
part) of stomach
increases the contractile
activity
Peristalsis +Retropulsion
food mixed with stomach
acid & enzymes and
forms -- chyme
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36. Initiation and production of
peristalsis
Co-ordinated pattern of smooth muscle contraction and
relaxation where wave of relaxation precedes wave of
contraction.
Rhythm determined by the BER
The number of spikes fired in a
Slow wave determines the force of each peristaltic contraction
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37. Mixing mechanism of peristalsis and
retropulsion
Peristaltic contractions
begins in stomach &
deepens near pylorus.
It strikes against the closed
pyloric sphincter with a
force & forced back into the
body of stomach.
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38. Mixing mechanism of peristalsis and
retropulsion
The backward movement of
the food is called Retropulsion.
The forward and backward
movements (caused by forceful
propulsion and retropulsion)
converting it into a semiliquid
paste called chyme.
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39. Gastric emptying.
A progressive wave of forceful
contraction of antrum, pylorus
(pyloric sphincter) and
proximal duodenum, all the
three function as a unit.
It occurs when chyme
decomposed to much smaller
units.
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48. DURING INTERDGESTIVE PERIOD
Migrating motor
complexes.
Peristaltic waves
Begins at oesophagus.
Remove remaining food
(Interdigestive
Housekeepers)
49. Migrating Motor Complexes.
RATE- Regular 5 cm/min every 60-90 min.
Close correlation between BER & MMC.
Associated with increase in gastric secretion, bile
flow & pancreatic secretion.
Abolished immediately with entry of food.
51. Mixing movements
Responsible for mixing of chyme with digestive
juices ( intestine, bile, Pancreatic)
Includes
Segmental contractions.
Pendular movements.
52. SEGMENTAL CONTRACTIONS.
Features
Most common, regular….Rhythmic
segmental contractions
Small segment contract & adjoining
segment relaxes.
Alternate contracted & relaxed
segment, so ring like appearance.
Function
Slow down transit time & increase
contact time with absorption.
Propels the chyme slowly towards
the colon.
53. SEGMENTAL CONTRACTIONS. (cont…)
Rate & duration.
12 times/ min ( duodenum)
8 times / min (ileum)
Types (2 types)
Eccentric ( lesser than 2 cm in length)
Concentric (longer than 2cm in length)
Control
Initiation
Occur only when slow waves (BER) produces spikes or action
potential.
Frequency
Directly related to frequency of slow waves & controlled by
pacemaker cells.
Strength
Proportional to frequency of spikes generated by slow waves.
54. PENDULAR MOVEMENTS.
Small constrictive waves sweep forward &
backward or upward & downward in
pendular fashion.
55. Propulsive movements
Involved in pushing the
chyme towards the aboral
end.
These include
Peristaltic contractions
Peristaltic rush.
56. PERISTALTIC CONTRACTIONS
Features.
Wave of contraction
preceded by wave of
relaxation.
Highly coordinated,
involve contraction of
segment behind bolus &
relaxation in front.
Consists of deep circular
ring @ 0.5 to 2 cm/sec.
Chyme move @ 1cm/min.
so 3-4 hrs from pylorus to
iliocecal valve.
57. Law of intestine.
Starling (1901)
Polarity of intestine, Polar conduction of intestine,
Electrical activity of intestine, Law of gut, Theory
of receptive relaxation.
“Peristaltic contraction travels from point of
stimulation in both direction but contraction
in oral direction disappears & persists in
aboral direction.”
58. PERISTALTIC CONTRACTIONS
Functions
Propel food.
Digestion & absorption.
Control
Initiation
Stimulus –
distention.(myentric
reflex).
Rate – 2-2.5 cm/sec.
Local stretch
Releases SEROTONIN
Activate sensory neurons
Stimulate myentric plexus
Activity travels in either
direction to release
Ach & sub P —Circular
constriction.
NO & VIP, ATP – Receptive
relaxation.
60. PERISTALTIC RUSH.
Very powerful peristaltic contractions
When intestinal mucosa irritated
Partly initiated by extrinsic nervous system & partly by
myentric reflex.
Begins in duodenum through entire length up to iliocecal
valve.
Relieve small intestine irritant or extensive distention.
E.g. ---Diarrhoea.
61. Movements of villi.
Features
Consists of alternate shortening & elongation of
villi by contraction & relaxation of muscles.
Initiation.
Local nervous reflexes.
Villikinin.– hormone from small intestine mucosa.
62. Movements of villi.
Functions
Help in emptying
lymph from central
lacteal into the
lymphatic system.
Increases surface area
so absorption
63. MOTILITY REFLEXES.
Gastroileal reflex.
Distention of stomach by food.
Reflex stimulation of vagus.
Relaxation of iliocecal sphincter
Intestinointesinal reflex.
Over distention of one segment
Relaxation of smooth muscle of rest of
intestine.
65. PARALYTIC ILEUS.
Adynamic ileus.
Pathophysiology –
intestinal motility
markedly decreased
leads to retention of
contents
Irregular distension of
small intestine by
pockets of gas & fluids.
Causes ---
Direct inhibition of
smooth muscle of small
intestine due to handling
of intestine. e.g.
Intraabdominal
operations & trauma.
Reflex inhibition due to
increased discharge of
noradrenergic fibres in
splanchnic nerves.
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66. INTESTINAL OBSTRUCTION.
Causes –
Due to tumors,
strictures and fibrotic
bands in abdomen.
Features –
Intestinal colic – severe pain
due to peristaltic rush.
Distension of small intestine
due to increased
intraluminal pressure.
Local ischemia.
Sweating , hypotension &
severe vomiting due to
stimulation of visceral afferent
nerves.
When obstruction in upper
part of small intestine—
antiperistaltic reflux causes
intestinal juices to flow into
stomach.
When obstruction in upper
part of small intestine— vomit
become more basic than
acidic.
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67. LARGE INTESTINE MOTILITY.
Slow wave activity.
Coordinated by BER Or Slow wave
activity (SWA)
Frequency of SWA gradually increase
down the LI.
9/min – iliocecal valve to 16/min at
sigmoid colon.
68. LARGE INTESTINE MOVEMENTS.
Functions
Absorption of water & electrolyte from chyme
(Proximal)
Storage of faecal matter.(Distal)
Contractile activity serves 2 main functions
Increase efficacy for absorption
Promotes excretion of faecal matter.
69. TYPES
Haustral shuttling.
Similar to segmental contractions
Circular muscle contractions– circular
rings
Longitudinal muscles contractions –
portion between rings bulge in bag like
sacs …… Haustrations.
Disappears within 60 sec.
Functions –
Mixing
Propulsion.
oPeristalsis
Progressive contractions preceded by receptive wave of
relaxation.
Take up to 42 hrs to travels up to colons.
70. TYPES
Mass movements.
Special types of peristaltic contractions in colon only.
3-4 times a day after a meals.
Contraction of the smooth muscle over a large area distal to the
constriction.
Force faecal matter into rectum initiate defecation reflex.
Can be initiated by
Gastro colic reflex
Intense stimulation of parasympathetic nerves.
Over distention of segment of colon.
73. DEFAECATION REFLEX.
Act of defaecation
Involves both – voluntary & reflex activity.
Reflex contraction of distal colon & rectum –
propel faecal matter in anal canal.
Reflex relaxation of internal anal sphincter.
Reflex relaxation with voluntary control of Ext
anal sphincter & voluntary contraction of
abdominal muscles.
74. EVENTS ASSOCIATED
Distention of rectum.—
Usually rectum is empty as
frequency of contractions is
greater in rectum than in
sigmoid colon leads to
retrograde movements of
fecal materials.
Gastrocolic reflex pushes
faeces into rectum
increases intrarectal
pressure passively.
75. Defaecation reflexes.
Intrinsic reflex.
Mediated by intrinsic nerve plexus.
Distension of rectum initiate afferents through myentric
plexus. --- Initiate peristalsis in descending colon, sigmoid
colon, rectum –-- Increase intra-rectal pressure. ---
Relaxation of internal anal sphincter.
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76. Spinal cord reflex.
Distension of rectum by faeces – afferent through pelvic
nerves to sacral part of spinal cord –-- reflex parasympathetic
discharge & pelvic splanchnic nerves to cause --- intense
peristaltic contractions --- rectal pressure above 55 mm Hg.
Relaxation of internal & external anal sphincter.
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77. EVENTS ASSOCIATED
Role of voluntary control on defaecation.
When defeacation is Not allowed --- voluntary
control maintains contraction of external anal
sphincter by pudendal nerves – internal sphincter
also closes --- rectum relaxes to accommodate
more faecal matter.
78. EVENTS ASSOCIATED
Role of voluntary control on defaecation.
When defeacation is allowed. --- external
sphincter relaxed voluntarily --- intra abdominal
pressure raised by Valsalva manoeuvre. --- smooth
muscle of distal colon & rectum contract forcefully
& propel faecal matter outside.
79. EVENTS ASSOCIATED
Role of voluntary control on defaecation.
Voluntary initiation of defaecation. --- before pressure
reached that relaxes both sphincters (less than 55mmhg &
more than 18mm Hg) ---by voluntary relaxing external
sphincter & contracting abdominal muscles.
80. APPLIED
Defaecation in Infants. – automatic emptying of
lower bowel without voluntary control.
Individuals with spinal cord transactions. ---
initially retention of faeces occurs --- later reflex
returns quickly --- as rectal pressure reaches 55
mm Hg reflex evacuation occurs automatically.
81. Role of dietary fibres.
Increases bulk of
faeces & play a role in
distending rectum.
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83. APPLIED
Hirschsprung’s disease –
Aganglionic mega colon -
-- congenital absence of
Auerbach’s plexus in wall of
rectosigmoid region.
Blockage of peristalsis & mass
contractions
Leads to dilatation of colon.
Treatment --- cutting
Aganglionic portion of pelvic-
rectal junction & anastomosing
cut ends.
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84. APPLIED
Constipation.---
Failure of voiding of faeces --- due to infrequent mass
movements in colon – faeces remain in colon for longer
time – becomes hard & dry due to fluid absorption.
Due to irregular bowel habits.
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