Git motility

GIT motility

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

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

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

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.
Thursday, June 18, 2020

5. CHEWING REFLEX
Voluntary act but
coordinated by
reflex.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

9. DEGLUTITION
Def–Passage of food from oral cavity to into
stomach.
Phases
Oral
Pharyngeal
Oesophageal
Thursday, June 18, 2020

10. ORAL
First stage
Voluntary
Bolus of food after
mastication put over
dorsum of tongue
Tongue forces back
into oropharynx
against hard palate.
Thursday, June 18, 2020

11. PHARYNGEAL
Second stage
Involuntaryby
swallowing reflex
Receptors–around
opening of pharynx
over tonsillar pillars
Afferents–Trigeminal,
Glossopharyngeal &
Vagus nerve.
Thursday, June 18, 2020

12. PHARYNGEAL
Center–Deglutition center
–in medulla & lower pons
(in NTS & Nucleus
Ambiguus)
Efferent–through 5
th
, 9
th
,
10
th
& 12
th
Effector organ–
pharyngeal musculature &
tongue (causes contraction)
Thursday, June 18, 2020

13. EVENTS DURING PHARYNGEAL
PHASE
Thursday, June 18, 2020

14. OESOPHAGEAL
Food pushed from upper
part of oesophagus to
stomach by oesophageal
peristalsis & helped by
greavity.
Thursday, June 18, 2020

15. APPLIED PHYSIOLOGY
Oesophagus–
fibromuscular tube
about 25 cm long
Seperated from pharynx
by UES(Upper
oesophageal sphincter
& stomach by LES
(Lower oesophageal
sphincter)
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

20. Physiology of gastric motility
Gastric musculature
Three layers of smooth
muscle fibres:
Outer longitudinal layer,
Middle circular layer
Inner oblique layer.
Thursday, June 18, 2020

21. Physiology of gastric motility
As per gastric
contractions
Stomach shows 2
regions
Oral region
Caudal region.
Thursday, June 18, 2020

22. Motor functions of stomach
Done by the gastric motility are:
Storage of food,
Mixing of food and
Slow emptying of food.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

24. Basal electrical rhythm.
Initiated by the
pacemaker cellslocated
near the fundus on the
greater curvature of the
stomach.
Thursday, June 18, 2020

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
Thursday, June 18, 2020

26. Factors affecting contractility
Thursday, June 18, 2020
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.
Thursday, June 18, 2020

28. Motility of empty stomach
Migrating motor complex
Hunger contractions
Thursday, June 18, 2020

29. Migrating motor complex
Peristaltic wave that
begins in the oesophagus
and travels through the
entire gastrointestinal
tract (migratory motor
activity) during
interdigestive period
Thursday, June 18, 2020

30. Interdigestive housekeepers
Remove any food remaining in the stomach
and intestines during interdigestive period
Thursday, June 18, 2020

31. Migrating motor complex
Rate--regular rate (5
cm/min)
Frequency-every 60–
90 min during the
interdigestive period
Motilin
Food entry
Thursday, June 18, 2020

32. Hunger contractions
Mild peristaltic
contractions
MMC–responsible
When become strong
fuse to form tetanic
contractionlasting for
2–3 min
Thursday, June 18, 2020

33. Gastric motility related to
meal
Receptive relaxation
Mixing peristaltic waves
Gastric emptying.
Thursday, June 18, 2020

34. Receptive relaxation
Food stimulates the
stretch receptors of
oral region produces
relaxation
vagovagal reflex
Cholecystokinin, VIP
or NO
Vagotomy abolishes
receptive relaxation
Thursday, June 18, 2020

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
Thursday, June 18, 2020

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
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

39. Gastric emptying.
A progressive wave of forceful
contraction of antrum, pylorus
(pyloric sphincter) and
proximal duodenum, allthe
three function as a unit.
It occurs when chyme
decomposed to much smaller
units.
Thursday, June 18, 2020

40. Factors regulating gastric
emptying.
Fluidity of chyme
Gastric factors
Duodenal factors
Other factors.
Thursday, June 18, 2020

41. Fluidity of chyme
The rate of gastric
emptying αfluidity.
Liquid empty faster
than solid
Thursday, June 18, 2020

42. Gastric factors
Volume of food in the stomach –directly
proportional.
Gastrin hormone. promotes gastric
emptying.
Type of food ingested –(Fastest)
Carbohydrate >protein > fats (slowest).
Thursday, June 18, 2020

43. Duodenal factors
Enterogastric reflex
Size of duodenal
osmoreceptors
Enterogastric
hormones
Cholecystokinin,
Secretin and
Gastric inhibitory
peptide.
Thursday, June 18, 2020

44. Other factors affecting gastric
motility..
Anger
and
Aggression
Depression
and
Fear
Vagotomy and
peptide Y
Thursday, June 18, 2020

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

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

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

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.

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

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.

59. PERISTALTIC CONTRACTIONS

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.

64. APPLIED
PARALYTIC ILEUS.
INTESTINAL
OBSTRUCTION.

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.

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

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

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

82. Thursday, June 18, 2020

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.
Thursday, June 18, 2020

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.
Thursday, June 18, 2020

85. THANK YOU.