This document discusses gastrointestinal motility and the movements of the small and large intestines. It describes the different types of movements that mix and propel food through the intestines, including segmental contractions, peristaltic contractions, and migrating motor complexes. These movements are controlled by pacemaker cells and nerves. The document also covers motility reflexes, large intestine movements like haustral shuttling and mass movements, and the defecation reflex. Motility allows for digestion, absorption of nutrients, and excretion of waste from the body.

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.