Git motility

DR NILESH KATE
MBBS,MD
PROFESSOR
ESIC MEDICAL COLLEGE, GULBARGA.
DEPT. OF PHYSIOLOGY
GIT
MOTILITY

OBJECTIVES.
 Mastication
 Lubrication of food by saliva
 Deglutition

INTRODUCTION
 Ingestion include 4
steps
 Placing food in mouth
 Mastication
 Lubrication
 Swallowing.
Thursday, June 18, 2020

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.

CHEWING REFLEX
 Voluntary act but
coordinated by
reflex.

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

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.

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.

DEGLUTITION
 Def – Passage of food from oral cavity to into
stomach.
 Phases
 Oral
 Pharyngeal
 Oesophageal

ORAL
 First stage
 Voluntary
 Bolus of food after
mastication put over
dorsum of tongue
 Tongue forces back
into oropharynx
against hard palate.

PHARYNGEAL
 Second stage
 Involuntary by
swallowing reflex
 Receptors – around
opening of pharynx
over tonsillar pillars
 Afferents – Trigeminal,
Glossopharyngeal &
Vagus nerve.

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)

EVENTS DURING PHARYNGEAL
PHASE

OESOPHAGEAL
 Food pushed from upper
part of oesophagus to
stomach by oesophageal
peristalsis & helped by
greavity.

APPLIED PHYSIOLOGY
 Oesophagus –
fibromuscular tube
about 25 cm long
 Seperated from pharynx
by UES (Upper
oesophageal sphincter
& stomach by LES
(Lower oesophageal
sphincter)

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.

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.

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.

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.

Physiology of gastric motility
 Gastric musculature
 Three layers of smooth
muscle fibres:
 Outer longitudinal layer,
 Middle circular layer
 Inner oblique layer.

Physiology of gastric motility
 As per gastric
contractions
 Stomach shows 2
regions
 Oral region
 Caudal region.

Motor functions of stomach
 Done by the gastric motility are:
 Storage of food,
 Mixing of food and
 Slow emptying of food.

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.

Basal electrical rhythm.
 Initiated by the
pacemaker cells located
near the fundus on the
greater curvature of the
stomach.

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

Factors affecting contractility
Initiate contraction.
Gastrin,
Histamine,
Nicotine,
Barium and K+
Inhibit contraction.
Enterogastrone,
Epinephrine,
Norepinephrine,
Atropine and Ca2+.

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.

Motility of empty stomach
 Migrating motor complex
 Hunger contractions

Migrating motor complex
 Peristaltic wave that
begins in the oesophagus
and travels through the
entire gastrointestinal
tract (migratory motor
activity) during
interdigestive period

Interdigestive housekeepers
 Remove any food remaining in the stomach
and intestines during interdigestive period

Migrating motor complex
 Rate -- regular rate (5
cm/min)
 Frequency - every 60–
90 min during the
interdigestive period
 Motilin
 Food entry

Hunger contractions
 Mild peristaltic
contractions
 MMC – responsible
 When become strong
fuse to form tetanic
contraction lasting for
2–3 min

Gastric motility related to
meal
 Receptive relaxation
 Mixing peristaltic waves
 Gastric emptying.

Receptive relaxation
 Food stimulates the
stretch receptors of
oral region produces
relaxation
 vagovagal reflex
 Cholecystokinin, VIP
or NO
 Vagotomy abolishes
receptive relaxation

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

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

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.

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.

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.

Factors regulating gastric
emptying.
 Fluidity of chyme
 Gastric factors
 Duodenal factors
 Other factors.

Fluidity of chyme
 The rate of gastric
emptying α fluidity.
 Liquid empty faster
than solid

Gastric factors
 Volume of food in the stomach – directly
proportional.
 Gastrin hormone. promotes gastric
emptying.
 Type of food ingested –(Fastest)
Carbohydrate >protein > fats (slowest).

Duodenal factors
 Enterogastric reflex
 Size of duodenal
osmoreceptors
 Enterogastric
hormones
 Cholecystokinin,
 Secretin and
 Gastric inhibitory
peptide.

Other factors affecting gastric
motility..
Anger
and
Aggression
Depression
and
Fear
Vagotomy and
peptide Y

GENERAL PRINCIPLES OF
GASTROINTESTINAL FUNCTIONS
 Motility. -- characteristics
 Functional syncytium.
 3layers of smooth muscles
of intestine.
 Functional types of
gastrointestinal
movements

GENERAL PRINCIPLES OF
GASTROINTESTINAL FUNCTIONS
 Propulsive
 Contraction ring
 Receptive relaxation.
 Mixing
 Peristaltic contractions
 Local constrictive contractions.

SMALL INTESTINE MOTILITY
 DURING INTERDIGESTIVE PERIOD
 DURING DIGESTIVE PERIOD
 MOTILITY REFLEXES.

DURING INTERDGESTIVE PERIOD
 Migrating motor
complexes.
 Peristaltic waves
 Begins at oesophagus.
 Remove remaining food
(Interdigestive
Housekeepers)

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.

DURING DIGESTIVE PERIOD
 Mixing movements
 Propulsive movements
 Movements of villi.

Mixing movements
 Responsible for mixing of chyme with digestive
juices ( intestine, bile, Pancreatic)
 Includes
 Segmental contractions.
 Pendular movements.

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.

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.

PENDULAR MOVEMENTS.
 Small constrictive waves sweep forward &
backward or upward & downward in
pendular fashion.

Propulsive movements
 Involved in pushing the
chyme towards the aboral
end.
 These include
 Peristaltic contractions
 Peristaltic rush.

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.

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.”

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.

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.

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.

Movements of villi.
 Functions
 Help in emptying
lymph from central
lacteal into the
lymphatic system.
 Increases surface area
so absorption

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.

APPLIED
 PARALYTIC ILEUS.
 INTESTINAL
OBSTRUCTION.

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.

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.

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.

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.

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.

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.

DEFAECATION REFLEX.
 Functional anatomy.
 Internal anal sphincter
(involuntary) circular
smooth muscle of
pelvirectal flexure.
 Parasymp– inhibitory
 Symp – excitatory.

DEFAECATION REFLEX.
 External anal
sphincter. Somatic
skeletal muscles
supplied by pudendal
nerves.

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.

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.

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.

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.

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.

EVENTS ASSOCIATED
 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.

EVENTS ASSOCIATED
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.

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.

Role of dietary fibres.
 Increases bulk of
faeces & play a role in
distending rectum.

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.

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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