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.