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.

Git motility

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Git motility

Similar to Git motility (20)

More from Dr Nilesh Kate

More from Dr Nilesh Kate (20)

Recently uploaded

Recently uploaded (20)

Git motility