intestine motility
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SMALL INTESTINE
LARGE INTESTINE MOTILITY
DR.NILESH KATE. M.D.
ASSOCIATE PROFESSOR,DEPARTMENT OF PHYSIOLOGY,
ESIC MEDICAL COLLEGE & HOSPITAL,GULBARGA.
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 neuronsStimulate myentric plexus
Activity travels in either direction to release
Ach & sub P —Circular constriction.NO & VIP, ATP – Receptive relaxation.
PERISTALTIC CONTRACTIONS
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.
Wednesday, April 22, 2015
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
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.
oPeristalsisProgressive 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.
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.
Wednesday, April 22, 2015
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.
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.
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
THANK YOU.
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