The stomach can be divided into three anatomic (A) and two functional regions (B)

Gastric reservoirTonic contractions Gastric reservoirTonic contractions

Gastric pumpPhasic contractionsGastric pumpPhasic contractions

BBFundusFundus

CorpusCorpusAntrumAntrum

PylorusPylorus

AA

Ehrlein Figure 1

The relaxation of the gastric reservoir is mainly regulated by reflexes. Three kinds of relaxation can be differentiated:

the receptive, adaptive and feedback-relaxation

Ehrlein Figure 2

Inhibitoryvagal fibre(NANC-inhibition)

Nutrients

CCKRelaxation of

gastric reservoir

ACH

Vaguscentre

1. Receptive relaxationMechanical

stimuli in the pharynx

3. Feedback relaxation

2. Adap tive relax ation

NutrientsTensionreceptors

Distension

NO + VIP et al.

The transport of digesta from the gastric reservoir into the antral pump is caused by two mechanisms: tonic contractions and peristaltic waves in the region of the gastric corpus

Ehrlein Figure 3

Tonic contraction

Peristaltic wave(Pump of the reservoir)Proximal

antrum

Backflow from antrum and flow from reservoir

Pylorus

Accumulationof chyme

The function of the gastric pump can be differentiated intothree phases: A: phase of propulsion, B: phase of emptying,C: phase of retropulsion and grinding

A Phase of propulsion Contraction of proximal antrum (PA)

B Phase of emptying Contraction of middle antrum (MA)

Propulsion of chyme into relaxingterminal antrum

+ duodenal contraction

Transpyloric and retrograde flow+ duodenal relaxation

C Phase of retropulsion Contraction of terminal antrum (TA)

Jet-like back-flow with grinding+ duodenal contraction

Phases

A B C

10 sec

Proximalantrum

Middleantrum

Terminal antrum

Pylorus

Duodenum

Pylorus

PA

MA

TA

closed

open

Ehrlein Figure 4

Liquids and small particles leave the stomach more rapidly than large particles.

This discrimination is called „sieving function“

Retropulsion of largeparticles and clearingof the terminal antrum

Phase of propulsion Phase of retropulsionPhase of emptying

Bulge

Rapid flow of liquids withsuspended small particlesand delayed flow of largeparticles towards pylorus

Emptying of liquids withsmall particles whereaslarge particles are retainedin the buldge of the terminalantrum

Antrum

Ehrlein Figure 5

Grinding of solid particles is caused by a forceful jet-like retropulsion through the small orifice of the

terminal antral contraction

Onset of terminal antral

contraction

Pylorus closing

Late phase of terminal antral

contraction

Pylorus closed

Ehrlein Figure 6

Antro-duodenal co-ordination: Contractions of the proximal duodenum cease during the phases of gastric emptying..

Ehrlein

Antralwaves

Middle antrum

Terminal antrum

Pylorus

Proximalduodenum

Lacking duodenal contractions

0 5 10 15 20 25 30 35 sec

1

Phases of gastric emptying

3.59.9 3.5 9.96.6open

closed

2 1 1 13 3 32 2 4

Figure 7

Because of different frequencies between antral and duodenal contractions,the duodenum can contract three to four times during an antral wave

sec

Several factors of gastric and duodenal motility co-operate and modulate gastric emptying:

Ehrlein

A. Rapid emptying is caused by tonic contractions of the reservoir (1a), deep peristaltic waves along the gastric body (1b), deep constrictions of the antral waves (2), a wide opening of the pylorus (3), a duodenal receptive relaxation (4) and peristaltic duodenal contractions (5). B. Delayed emptying due to feedback inhibition is caused by a prolonged relaxation of the reservoir (6a), shallow peristaltic waves along the gastric body ( 6b), shallow antral waves (7), a small pyloric opening (8), a lacking duodenal relaxation (9) and segmenting duodenal contractions (10).

Figure 8

510

A. Rapid emptying

Pylorus1a

1b2

34

7

89

B. Delayed emptying

6a

6b

Balance between gastric reservoir and antral pump

Figure 9Ehrlein

Gastro-gastric reflexes

Excitatory reflex

Inhibitoryreflex

Enhanced and prolonged relaxation of reservoir

Distension

Antral pump switched on

and intensified

Disten-sion

Pyloric activity is modulated by antral inhibitoryand duodenal excitatory reflexes

Figure 10Ehrlein

Descendinginhibitory reflex

causing pyloric relaxation

Contraction of middle antrum

Ascendingexcitatory reflex

causing pyloric contractions

and increasing pyloric tone

Duodenal stimuli

An additional function of the pyloric sphincter is to prevent duodeno-gastric reflux

Figure 11

Pyloric closure

Inhibition

Stimulation

0.5 ml oleic acid + bile into duodenum

Antrum

Pylorus

Duod. bulb

Duodenum

closed

open

Ehrlein

Duodenal stimuli like oleic acid inhibit antral contractions, evoke duodenal contractions, increase pyloric tone and elicit frequent pyloric contractions

Solids and liquids of the gastric chyme are emptied with different velocities.

Ehrlein

Lag phase

Time (min)

Viscouscontent

Liquid content

Solids100

80

60

40

20

00 20 40 60 80 100 120

Gas

tric

vo

lum

e ( %

)

Figure 12

Emptying of liquids is exponential, emptying of large solid particles only begins after sufficient grinding (lag phase). Afterwards the viscous chymeis mainly emptied in a linear fashion

Nutrients in the gut activate a feedback control and modulate gastric and duodenal motility

Ehrlein Figure 13

Gastrointestinal motor patterns after a non-caloric and a nutrient meal

Antrum

Pylorus

closed

open

Duodenalbulb

MiddleDuodenum

Reduced force ofantral contractions

Reduced pyloric opening

Reduced peristaltic waves

Enhancedsegmenting activity

Non-caloric meal Nutrient meal

Feedback control causes

The feedback regulation of gastric emptying is performed by entero-gastric reflexes and release of intestinal hormones

Ehrlein Figure 14Ehrlein Figure 14

It causes enhanced relaxation of the gastric reservoir, inhibition of the antral pump, and reduced opening of the pyloric sphincter.

Vagalcenter

Inhibitoryvagal fibers

NO, VIP et al.

Senso

ric

affe

rent

fiber

s

CCK

ACHEnhancedrelaxation

andstorage

Stimulating cholinergicvagal fibers

Nutrients Long chain fatty acids Amino acids Dipeptids GlucoseOsmolalityHydrochloric acid

Reduced openingof pyloric sphincter

Reduced contraction

Backflow

+

+_

ACH

Contractile patterns of the small intestine

Ehrlein

Peristaltic Stationary Clusterswaves contractions of contractions

1 minute 1 minute 1 minute

oral

aboral

Figure 15

The most frequent patterns are peristaltic waves (dashed lines), stationary contractions (arrows), and clusters of contractions, which occur either stationary at an intestinal segment or slowly migrate aborally

Phase III of the interdigestive motility designated as ”migrating motor complex” (MMC)

oral

aboral Aboral migration of phase III

Velocity of the peristaltic waves

1 minuteJejunal phase III (MMC)

Ehrlein Figure 16

Rectangles: strain gauge transducers, Data of dog.

Pathological contractile patterns of the proximal intestine

Antiperistaltic waves

1 minute

Jeju

num

oral

aboral

Aboral giant contractions

1 minute

0,2 Newton

Duo

denu

m

oral

aboral

Ehrlein Figure 17

Alternating peristaltic (blue arrows) and antiperistaltic waves (red arrows). Giant contractions sometimes originate as a cluster.

Ehrlein Figure 18

Different kinds of contractile patterns are caused by different kinds of excitation

Excitation Excitation

PP 1

2

3

1

2

3

PP

Stationary Singlesegmenting contractions peristaltic waves

1, 2, 3 successive pacesetter potentials (PP)

Stationary segmenting contractions are produced by brief excitation of ashort intestinal segment

Single peristaltic waves are produced by short excitations of a long intestinal segment

Time course

Clustered contractions are produced by a long lasting excitation of a short intestinal segment. The cluster is stationary when the excitation remains at the same segment. When the excitation slowly moves aborally the cluster of contractions migrates along the intestine.

Stationary cluster Migrating cluster

Time course

Stationary excitation Aboral migrating excitation

1

2

3

1

2

3

Ehrlein Figure 19

Origin of clustered contractions

1, 2, 3 successive pacesetter potentials (PP)

Luminal stimuli elicit vago-vagal reflexes which activate integrating and program circuits of the enteric nervous system. These activate specific motorneurones responsible for specific contractile patterns.

Ehrlein Figure 20

Central and peripheral control of contractile patterns

Intestinalwall

Vagalcentre

Intestinallumenl

Peptide (CCK) ReceptorsGlucose - OsmolalityLong chain fatty acidsAmino acids

Sensory neurons

Vago-vagal reflexes

InterneuronsIntegrating circuits

Program circuits

Enteric nervous system

Motorneurons Contractilepatterns

Postprandial contractile patterns of the small intestine

0,2 Newton

oral

aboral

Ehrlein Figure 21

They are composed of stationary segmenting contractions (green arrows), stationary and migrating clusters of contractions (red horizontal lines)

and single short peristaltic waves (dotted lines).

The phase III of the migrating motor complex originates simultaneously at the stomach and duodenum and migrates within 90 to 120 minutes along the small intestine (dog)

Interdigestive CyclesPhases

Sporadicperistaltic waves

Segmenting contractionsand single

peristaltic waves

Motorquiescence of stomach

and duodenum

Contractionof reservoir

Pylorus

Aboral migration

Accumulation of residues

of chyme

Phase IIPhase I

Stomach

Duodenum

Jejunum

Ileum

Phase III

Phase III

III I II III

Phase III

Phase II

Phase I

Forcefulperistaltic

waves

Motorquiescence

Ehrlein Figure 22

The interdigestive motility consists of three phases

The antral waves are associated with a wide opening of the pylorus and inhibition of duodenal contractions followed by duodenal peristaltic waves occurring at maximal frequency.

Ehrlein Figure 23

Middle Antrum

Pyloric diameter

Duodenal bulb

Duodenum

Gastric phases III

1 min

PAP P

0 mm

6 mm

Stomach is cleaned of residues of chyme and secretions.

Gastric phase III consisting of 1 - 3 forceful contractions of the gastric reservoir and lumen occluding peristaltic

waves occurring at intervals of 2-3 min

Phase III (MMC) of the small intestine

Ehrlein

Intestinal phase III

oral

Successsiveperistaltic waves

Chyme

Slow aboralmigration of phase III

aboral

Time (about 20 sec)

Time (about 20 sec)

Figure 24

The peristaltic waves clean the intestinal segment from chyme which accumulates aborally. Because the successive waves start and end further aborally the phase III slowly migrates distally

Postprandial motility is characterised by a lower amplitude of the antral waves occurring at maximal frequency, rhythmic pyloric opening and closure and co-ordinated duodenal contractions occurring in sequencewith the antral waves

Ehrlein

Antrum

Pylorus

Duodenum

5 min

MealPhase III

closed

open

Fed motor pattern

Figure 25

Ingestion of a meal suppresses the interdigestive motility and induces a fed motor pattern

C: A special feature of the large intestine are multiple segmenting contractions of long duration migrating aborally. They divide digesta into boli pushing them slowly aborally. The motility tracings show a rise of the baseline superimposed by phasic contractions

C: A special feature of the large intestine are multiple segmenting contractions of long duration migrating aborally. They divide digesta into boli pushing them slowly aborally. The motility tracings show a rise of the baseline superimposed by phasic contractions

Ehrlein Figure 26

Contractile patterns of the large intestine

AA

BB

CC

Colonic segmenting contractions migrating aborally

aboral migration

small aboral flow

backflow low propulsion

Shallow peristaltic waves of caecum and colon

Shallow peristaltic waves at haustrated colon

slow aboral propulsion

Motility of the large intestine in pig

A: Haustral movements of the caecum result in clustered contractions. B: The ileum is emptied by giant contractions. They occur either isolated or in co-ordination with peristaltic waves of the caecum and colon. Additional colonic waves originate at the beginning of the colonic coil.

Caecum

Ehrlein

J1J2

C1 C2 C3

Co1

Co2

Co3

Ileum

Colon

Distal colon

Caecum

C1

C2

C3

1 min

Ileum - Caecum - Colon

1 min

Co3

Co1

Co2

C1

J2

J1Giant contractions

Colonic wave

Figure 27

AA BB

SC1

SC2

SC3

Spiral colon

Peristaltic wave

Caecal motility is characterised by peristaltic andantiperistaltic waves. In the colon peristaltic wavesand giant contractions are the dominant feature. Inthe spiral colon prolonged segmenting contractionsdivide digesta into boli and push them distally.

CaecumColon

Co1

Co2 Co3

Co4

C2 C3 C4

Ileum

SC1

SC2SC3

C1

Co2

Spiral colon

Caecum Colon

C4

C3

C2

C1

Co1

Co2

1 min1 min

Co3

C1

Co1

Co2

Co4

Giantcontraction

Ehrlein Figure 28

Motility of caecum and colon in sheep.

J1

C1

C2

C3

C4

C5

1 min

Colon

Co1

Co2

Co3

Giant contractions

1 min

Caecum

Caecal motility is characterised by peristaltic and antiperistaltic waves. Migrating segmenting contractions are the dominant feature of the single haustrated colon.

Co3J1 Co2

Co1

C1

C2

C3 C4 C5

Colon

Caecum

Ileum

Ehrlein Figure 29

Motor patterns of the large intestine in rabbits

A: Slow paper speed. The CMC’s occur at all parts of the colon at intervals of 20-30 min. B: High paper speed. The CMC’s consist of a rise of the baseline super-imposed of phasic contractions. The onset of the CMC‘s obviously differs along the colon (indicated by lines).

A: Slow paper speed. The CMC’s occur at all parts of the colon at intervals of 20-30 min. B: High paper speed. The CMC’s consist of a rise of the baseline super-imposed of phasic contractions. The onset of the CMC‘s obviously differs along the colon (indicated by lines).

Ehrlein

AA BBColonic motor complex (CMC)

aboral

oral

Phasiccontractions

15 min 5 min

Figure 30

Colonic motor complexes (CMC’s) of the canine colon

(1) Normal segmenting contractions of the proximal jejunum (2) Start of a retrograde giant contraction in proximal jejunum; (3) Retropelled digesta reach the duodenum and (4) are forced across thewidely opened pylorus into the antrum; (5) The giant contraction proceeds to the antrum, the chyme accumulates in the gastric reservoir.

1 2 34 5

1 2 3 4 5

Antrum

Pylorus (P)

Bulbus

Prox. duod.

Distal duod.

closed

open

1 min

Retrograde giant contraction Vomiting

Duodenum

P

P

Stomach

P

Jejunum

Ehrlein Figure 31

Retrograde giant contraction followed by vomiting