The stomach can be divided into three anatomic (A)
and two functional regions (B)
A
B
Fundus
Pylorus
Antrum
Corpus
Ehrlein
Gastric pump
Phasic contractions
Gastric reservoir
Tonic contractions
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
Mechanical
stimuli in the
pharynx
1. Receptive
relaxation
3. Feedback
relaxation
2. Adap
relax
Vagus
centre
tive
ation
Tension
receptors
ACH
NO + VIP et al.
CCK
Nutrients
Inhibitory
vagal fibre
(NANC-inhibition)
Nutrients
Relaxation of
gastric reservoir
Distension
Ehrlein
Figure 2
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
Tonic
contraction
Pylorus
Proximal
antrum
Accumulation
of chyme
Peristaltic wave
(Pump of the reservoir)
Backflow from antrum and flow from reservoir
Ehrlein
Figure 3
The function of the gastric pump can be differentiated into
three phases: A: phase of propulsion, B: phase of emptying,
C: phase of retropulsion and grinding
Phases
ABC
A Phase of propulsion
Contraction of proximal antrum (PA)
Pylorus
Propulsion of chyme into relaxing
terminal antrum
+ duodenal contraction
Proximal
antrum
PA
Middle
antrum
B Phase of emptying
Contraction of middle antrum (MA)
Terminal
antrum
Transpyloric and retrograde flow
+ duodenal relaxation
MA
closed
Pylorus
open
TA
Duodenum
10 sec
Ehrlein
C Phase of retropulsion
Contraction of terminal antrum (TA)
Jet-like back-flow with grinding
+ duodenal contraction
Figure 4
Liquids and small particles leave the stomach
more rapidly than large particles.
This discrimination is called „sieving function“
Phase of propulsion
Phase of emptying
Phase of retropulsion
Antrum
Bulge
Rapid flow of liquids with
suspended small particles
and delayed flow of large
particles towards pylorus
Ehrlein
Emptying of liquids with
small particles whereas
large particles are retained
in the buldge of the terminal
antrum
Retropulsion of large
particles and clearing
of the terminal antrum
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
Ehrlein
Late phase
of terminal antral
contraction
Pylorus closed
Figure 6
Antro-duodenal co-ordination: Contractions of the proximal
duodenum cease during the phases of gastric emptying..
Phases of gastric emptying
Middle antrum
Terminal
antrum
Antral
waves
closed
Pylorus
open
9.9
Proximal
duodenum
1
2
3
6.6
3.5
1
2
3
9.9
3.5
1
2
3
4
sec
1
Lacking duodenal contractions
0
5
10
15
20
25
30
35 sec
Because of different frequencies between antral and duodenal contractions,
the duodenum can contract three to four times during an antral wave
Ehrlein
Figure 7
Several factors of gastric and duodenal motility
co-operate and modulate gastric emptying:
A. Rapid emptying
B. Delayed emptying
Pylorus
4
3
1a
9
1b
5
2
6a
8
10
6b
7
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).
Ehrlein
Figure 8
Balance between gastric reservoir and antral pump
Gastro-gastric reflexes
Enhanced and prolonged
relaxation of reservoir
Inhibitory
reflex
Distension
Distension
Antral pump
switched on
and intensified
Ehrlein
Excitatory
reflex
Figure 9
Pyloric activity is modulated by antral inhibitory
and duodenal excitatory reflexes
Descending
inhibitory reflex
causing
pyloric relaxation
Ascending
excitatory reflex
causing
pyloric contractions
and increasing
pyloric tone
Duodenal stimuli
Ehrlein
Contraction of
middle antrum
Figure 10
An additional function of the pyloric sphincter
is to prevent duodeno-gastric reflux
Pyloric closure
Antrum
closed
Pylorus
open
Inhibition
Duod. bulb
Duodenum
Stimulation
0.5 ml oleic acid + bile
into duodenum
Duodenal stimuli like oleic acid inhibit antral contractions, evoke duodenal
contractions, increase pyloric tone and elicit frequent pyloric contractions
Ehrlein
Figure 11
Solids and liquids of the gastric chyme are emptied with
different velocities.
Lag phase
100
Solids
80
Viscous
content
60
40
Liquid
content
20
0
0
20
40
60
80
100 120
Time (min)
Emptying of liquids is exponential, emptying of large solid particles only
begins after sufficient grinding (lag phase). Afterwards the viscous chyme
is mainly emptied in a linear fashion
Ehrlein
Figure 12
Nutrients in the gut activate a feedback control and
modulate gastric and duodenal motility
Non-caloric meal
Nutrient meal
Feedback control causes
Antrum
closed
Pylorus
open
Duodenal
bulb
Middle
Duodenum
Reduced force of
antral contractions
Reduced
pyloric opening
Reduced
peristaltic waves
Enhanced
segmenting activity
Gastrointestinal motor patterns after a non-caloric and a nutrient meal
Ehrlein
Figure 13
The feedback regulation of gastric emptying is performed
by entero-gastric reflexes and release of intestinal hormones
Vagal
center
Nutrients
Long chain fatty acids
Amino acids
Dipeptids
Glucose
Osmolality
Hydrochloric acid
+
_
+
Inhibitory
vagal fibers
Stimulating cholinergic
vagal fibers
ACH
NO, VIP et al.
CCK
ACH
Reduced opening
of pyloric sphincter
Enhanced
relaxation
and
storage
Backflow
Reduced
contraction
It causes enhanced relaxation of the gastric reservoir, inhibition of the antral
pump, and reduced opening of the pyloric sphincter.
Ehrlein
Figure 14
Contractile patterns of the small intestine
Peristaltic
waves
oral
aboral
1 minute
Stationary
contractions
1 minute
Clusters
of contractions
1 minute
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
Ehrlein
Figure 15
Phase III of the interdigestive motility
designated as ”migrating motor complex” (MMC)
Jejunal phase III (MMC)
oral
aboral
Aboral migration
of phase III
1 minute
Velocity of the
peristaltic waves
Rectangles: strain gauge transducers, Data of dog.
Ehrlein
Figure 16
Pathological contractile patterns of the proximal intestine
Antiperistaltic waves
Aboral giant contractions
oral
oral
Jejunum
Duodenum
0,2 Newton
aboral
1 minute
aboral
1 minute
Alternating peristaltic (blue arrows) and antiperistaltic waves (red arrows).
Giant contractions sometimes originate as a cluster.
Ehrlein
Figure 17
Different kinds of contractile patterns
are caused by different kinds of excitation
Stationary
segmenting contractions
Single
peristaltic waves
Excitation
Excitation
PP
1
1
PP
2
2
3
3
Time
course
Stationary segmenting contractions
are produced by brief excitation of a
short intestinal segment
Ehrlein
Single peristaltic waves are produced by
short excitations of a long intestinal segment
1, 2, 3 successive pacesetter potentials (PP)
Figure 18
Origin of clustered contractions
Stationary cluster
1
Migrating cluster
1
2
2
3
3
Time
course
Stationary excitation
Aboral migrating excitation
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.
1, 2, 3 successive pacesetter potentials (PP)
Ehrlein
Figure 19
Central and peripheral control of contractile patterns
Vagal
centre
Intestinal
wall
Vago-vagal reflexes
Interneurons
Integrating circuits
Sensory neurons
Motorneurons
Program circuits
Contractile
patterns
Enteric nervous system
Intestinal
lumenl
Peptide (CCK) Receptors
Glucose - Osmolality
Long chain fatty acids
Amino acids
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
Postprandial contractile patterns of the small intestine
oral
0,2 Newton
aboral
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).
Ehrlein
Figure 21
The interdigestive motility consists of three phases
III
Interdigestive Cycles
Phases
II
I
Phase III
Stomach
Phase III
Pylorus
Duodenum
Accumulation
of residues
of chyme
Jejunum
Phase I
Contraction
of reservoir
Forceful
peristaltic
waves
Motor
quiescence
of stomach
and duodenum
III
Phase II
Sporadic
peristaltic waves
Segmenting
contractions
and single
peristaltic waves
Phase II
Motor
quiescence
Ileum
Phase I
Phase III
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)
Ehrlein
Figure 22
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
Gastric phases III
Middle Antrum
0 mm
Pyloric diameter
6 mm
Duodenal bulb
Duodenum
1 min
A
P
P
P
Stomach is cleaned of residues
of chyme and secretions.
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
Phase III (MMC) of the small intestine
Intestinal phase III
oral
Successsive
peristaltic waves
Chyme
Slow aboral
migration of
phase III
aboral
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
Ehrlein
Figure 24
Ingestion of a meal suppresses the interdigestive
motility and induces a fed motor pattern
Phase III
Meal
Fed motor pattern
Antrum
closed
Pylorus
open
Duodenum
5 min
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 sequence
with the antral waves
Ehrlein
Figure 25
Contractile patterns of the large intestine
Shallow peristaltic waves of caecum and colon
A
backflow
low propulsion
Shallow peristaltic waves at haustrated colon
B
small aboral flow
Colonic segmenting contractions migrating aborally
C
slow aboral propulsion
aboral migration
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
Motility of the large intestine in pig
A
Caecum
Ileum - Caecum - Colon
B
J1
C1
Giant contractions
J2
C2
C1
C3
Colonic wave
Co1
1 min
Co2
Co3
Colon
Co2
Ileum
J1
J2
Caecum
Co1
Distal
colon
Ehrlein
C1 C2 C3
Co3
1 min
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.
Figure 27
Motility of caecum and colon in sheep.
Caecum
Spiral colon
Peristaltic
wave
C4
Colon
Giant
contraction
C1
C3
SC1
Co1
C2
SC2
C1
Co2
Co1
Co3
Co2
Co4
SC3
Ileum
C2 C3 C4
Co1
C1
Colon
Co2
Caecum
Co2
Co3
SC1
SC2
SC3
Co4
Spiral colon
Ehrlein
1 min
1 min
Caecal motility is characterised by peristaltic and
antiperistaltic waves. In the colon peristaltic waves
and giant contractions are the dominant feature. In
the spiral colon prolonged segmenting contractions
divide digesta into boli and push them distally.
Figure 28
Motor patterns of the large intestine in rabbits
Colon
Caecum
Giant contractions
J1
Co1
C1
Co2
C2
Co3
1 min
Ileum
Co3 Co2
J1
C3
Co1
C1
Colon
C2
C4
C5
Caecum
C3
C4
C5
1 min
Caecal motility is characterised by peristaltic and antiperistaltic waves. Migrating
segmenting contractions are the dominant feature of the single haustrated colon.
Ehrlein
Figure 29
Colonic motor complexes (CMC’s) of the canine colon
A
oral
B
Colonic motor complex (CMC)
Phasic
contractions
15 min
5 min
aboral
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 superimposed of phasic contractions. The onset of the CMC‘s obviously differs
along the colon (indicated by lines).
Ehrlein
Figure 30
Retrograde giant contraction followed by vomiting
Retrograde
giant contraction
Vomiting
Distal duod.
Prox. duod.
Bulbus
closed
Pylorus (P)
open
Antrum
1
2 34 5
Duodenum
1 min
P
Jejunum
1
2
Ehrlein
P
3
P
Stomach
5
4
(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 the
widely opened pylorus into the antrum; (5) The giant contraction proceeds
to the antrum, the chyme accumulates in the gastric reservoir.
Figure 31