INTESTINE MOTILITY

INTESTINE MOTILITY

1. SMALL
INTESTINE
LARGE
INTESTINE
MOTILITY
DR.NILESH KATE.
M.D.
ASSOCIATE PROFESSOR,
DEPARTMENT OF PHYSIOLOGY,
ESIC MEDICAL COLLEGE & HOSPITAL,
GULBARGA.

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

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

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

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

6. 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.

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

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

9. 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.

10. 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.

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

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

13. 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.

14. 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.”

15. 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.

16. PERISTALTIC CONTRACTIONS

17. 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.

18. 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.

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

20. 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.

21. APPLIED
PARALYTIC ILEUS.
INTESTINAL
OBSTRUCTION.

22. 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.
Wednesday, April 22, 2015

23. 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.
Wednesday, April 22, 2015

24. 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.

25. 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.

26. 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.

27. 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.

28. DEFAECATION REFLEX.
Functional anatomy.
Internal anal sphincter
(involuntary) circular
smooth muscle of
pelvirectal flexure.
Parasymp– inhibitory
Symp – excitatory.
External anal sphincter.
Somatic skeletal muscles
supplied by pudendal
nerves.

29. 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.

30. 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.

31. 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.
Wednesday, April 22, 2015

32. 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.
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.
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.

33. 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.

34. 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.
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.
Wednesday, April 22, 2015

35. THANK YOU.