Gastrointestinal motility involves propulsive and mixing movements regulated by neural and hormonal mechanisms. The mouth chews food through mastication, preparing it for swallowing. Swallowing has voluntary and involuntary phases moving food through the esophagus to the stomach. The stomach mixes and slowly empties food through peristalsis. Disorders can occur with swallowing or lower esophageal function. Vomiting is a reflex to expel stomach contents. The small intestine further mixes and propels contents through segmentation and peristalsis regulated by hormones and nerves. The large intestine absorbs water before defecation, regulated by intrinsic and extrinsic reflexes.

1. GASTROINTESTINAL MOTILITY
They are basically 2 types of motility:
Propulsive movement Mixing movement
Propulsive movement: This moves the food from one segment of the gastrointestinal to
another while mixing movement allows food to be properly mixed.
Both the propulsive & mixing movement are carefully, regulated so that food does not move
too fast or too slow. Mixing movement also ensures that food is adequately &
proportionately mixed so that the food would not be over or under mixed. This is under
hormonal and neural regulatory mechanisms to ensure that their movement occurs
optimally.

2. THE MOUTH
Chewing/Mastication
This is the process by which food is broken down into swallowable units or swallowable
consistency.It is the 1st
mechanical process by which food substances are cut into smaller
particles and ground into a soft bolus. Chewing is essentially a mixing movement as it
ensures that food is properly mixed with saliva. It is a reflex process mainly.
Importance of chewing/mastication
Chewing makes for easy swallowing
It prevents damage of the walls of the GIT/excoriation
It enables the cellulose cell wall around the nutrient portion of fruits and vegetables to be
broken down so as to liberate the hidden nutrients.
The reflex mechanism of the chewing process involves; Reflex inhibition of the chewing
muscle as food is placed in the mouth.

3. The presence of food in the mouth reflexely
inhibits the muscles of mastication causing the jaw to drop, the muscles of mastication
are stretched. Thus leads to contraction of the muscles of mastication causingthe
mouth to close, compressing the food in the mouth, further causes the jaw to drop
leading again to stretching of the mastication muscles and the cycle continues.
Therefore movement of mastication are
i.Opening and closure of the mouth
ii. Rotation of the jaw
iii. Protraction and retraction of the jaw.

4. SWALLOWING/DEGLUTITION
This is a process whereby properly masticated food moves from the mouth through the
esophagus to the stomach.
There are 2 phases in swallowing; Voluntary phase
Involuntary phase
Voluntary phase of swallowing: Is the first Voluntary act using the tongue to roll the
properly masticated food into a bolus and pushing it superiorly and posteriorly against the
palate.
Involuntary swallowing: This phase is divided into 2; The pharyngeal phase
The esophageal phase

5. Pharyngeal phase: Occurs in the pharynx while the
esophageal occurs in the esophagus. It is essentially a reflex. The presence of the bolus of
the food in the posterior mouth stimulates swallowing receptors that are present in the
pharynx. This receptors then generate impulses.
Swallowing centres are located in the medulla close to the
nucleus of tractus solitarius. The swallowing centres then decodes and sends appropriate
responses through the efferent pathway to mediate swallowing responses. The responses
includes;
Closure of the posterior nares by the soft palate so as to ensure that the swallowed food is
not regurgitated through the nostrils.

6. There is a tight approximation of the palatopharyngeal
folds (i.e they move close together) thus creating a tiny sagittal slit that selectively
allows properly masticated food to pass through while food that are not properly
masticated are not allowed to pass through.
There is tight approximation of the vocal cords accompanied by the superoanterior
lifting of the larynx causing the upper part of the esophagus to open. This reflex
inhibits the upper esophageal sphincter causing it to relax and open up. This ensures
that the swallowed food enters the esophagus and not the trachea.
Contraction of the pharyngeal muscles: this pushes
down the bolus of food that travels down the esophagus. This initiates the peristalsis
movement.

7. ESOPHAGEAL PHASE OF SWALLOWING
Occurs entirely in the esophagus and is propelled by the force of contraction that occurs in
the pharynx. There is relaxation ahead of the bolus which allows easy propulsion of
swallowed food. Therefore the LES relaxes to allow food passage into the stomach and
after it constricts to prevent reflux.
There are 2 types of peristalsis;
Primary peristalsis/peristaltic movement
Secondary peristalsis.
The analward movement of food from esophagus into the stomach does not depend on
gravitational pull.
Primary peristalsis is a continuation of pharyngeal peristalsis.
Usually this peristalsis is enough to initiate esophageal peristalsis and also

8. push food.There is accumulation
of food in the lower esophagus and this generates the 2nd type of contractions at the
lower esophagus. This 2nd peristalsis is called secondary peristalsis which then pushes
the food down to the stomach.
Factors that affect peristalsis
 The appearance of the ring of contraction behind the swallowed bolus and reflex
relaxation of the bolus ensures that the swallowed food finds its way easily to the
subsequent segments.

9.  The polarity of the enteric nervous system. To test this, some people cut a strip
of esophagus and sutured the two ends, peristalsis continued. Another part of
the gut was removed and later sutuered back and peristalsis Returned.
However,if a section of the esophagus is cut, innervated and sutured back, the
peristalsis is disturbed as polarity is now inverted.

10. DISORDERS OF SWALLOWING
When there is a problem with swallowing, there is a failure of movement of food in
the mouth to the stomach. Several factors can predispose to this;
 Damage to 5th
,9th
, 10th
and 12th
cranial nerves. Messages cannot be sent to
swallowing centres;
 Paralysis of swallowing muscles of the pharynx.
 Diseases like polio myelitis or encephalitis.
 Failure of neuromuscular transmission as occurs in myasthenia gravis.

11. Disorders of swallowing associated with the
lower esophageal sphincters.
Achalasia: Primary disorder of the lower esophagus .1st
described in 1672 by Sir Thomas
Willis (Circle of Willis). The term achalasia was conned in 1929 by Hurt and Rake. It is
characterized;
By failure of the lower esophageal sphincter to relax when swallowing/failure of the
hypertensive esophageal sphincter to relax upon swallowing

12. There is usually absence of peristalsis (presence of
weak peristalsis). The cause of achalasia is not very well defined but its known to be
associated with the following
• Over competence of LES causing Increase resting tension.
• Incomplete or failure of lower esophageal sphincter to relax upon swallowing.
• Weak esophageal peristalsis via destruction of myenteric plexus.
Symptoms:
 Dysphagia
 Chest pain
 Heart burn
 Weight loss
Regurgitation

13. Treatment:
 Use of calcium channel blockers
 Intra sphincteric administration of Botulinium toxin at the level of the Lower
esophageal sphincter to inhibit acetylcholine release.
 Pneumatic dilation of the lower esophagealsphincter.
 Myotomy, a surgical procedure
Lower esophageal incompetence
In this condition, the lower Esophageal sphincter fails to contract appropriatly i.e it
remains open or partially open. In this condition, there is usually reflux of acidic gastric
juice in the lower esophagus. Since this area is not equipped to handle the acid content
of the gastric acid, there is then excoriation of this area by acid.

14. Symptoms
Excoriation of the lower esophagus
Chest pain
Heart burn
Treatment
Use of acid inhibitors
Use of antacids.
Surgical procedure.

15. VOMITTING/EMESIS
It is reflex process. It usually caused by irritation, over distension and over excitability of
upper intestinal tract (i.efrom the mouth to stomach). There are receptors/vomiting
receptors at the pharynx,esophagus,stomach,and duodenum which sends sensory signals
through the vagal and sympathetic fibers to the vomiting center in the brainstem. The
vomiting center then decodes the stimuli and appropriate response are sent through 5,7,9,
10th and 12th cranial nerves to the upper GIT and some are sent through the spinal nerves
to the abdominal muscles and diaphragm.
Note: Vomiting is the opposite/reverse of swallowing.

16. RESPONSES TO VOMITING REFLEX
• Deep breath
• Upward movement of soft palate and closure of glottis
causes closure of the posterior nares .
• Superior and anterior movement of the larynx so as to open up the upper
esophageal sphincter.
• Contraction of the abdominal muscles and diaphragm which causes increase in
intragastric pressure.
• Opening of the lower esophageal sphincter allowing expulsion of gastric content
into the esophagus. Note: These events occur almost simultaneously.

17. CAUSES OF VOMITTING
1. Psychological factors can mediate vomiting through the factors not well
known but the pathway passes through the brain straight to the VMC and cause
vomiting.
2. Some drugs are known to mediate vomiting without exciting or distending
the upper GIT e.g Morphine acts on the chemoreceptor trigger zone which is
located on the floor of the 4th ventricle.

18. 3. Vomiting can also be caused by motion sickness which is a result of stimulation of
labrynthine receptors in the inner ear which generate stimuli which is sent to vestibular
nuclei which is sent to the cerebellum then to chemoreceptor trigger zone to the VMC.

19. GASTRIC MOTILITY
There are 3 main types of motor activity of the
stomach;
a.Receptive relaxation
b. Mixing/peristaltic movement
c.Slow emptying
RECEPTIVE RELAXATION
It allows the stomach to accommodate more and more food until its capacity is reached.
The fundus and upper part of the stomach relaxes to accommodate food. The capacity is
different for different individual usually greater in the males.
As food enters the stomach,it forms concentric circles with the newest food lying closest
to the esophageal opening and the oldest food lying nearest to the outer wall of the
stomach. The food causes stretching of the wall which initiates a reflex ie vagovagal
reflex from stomach to the brain and back to the stomach.This causes reduction of
muscular tone which leads to relaxation to accommodate more food upto a limit.
NB: It is vagally mediated.

21. MIXING MOVEMENT
It ensures that the food is properly mixed with gastric secretion. Once there's food in the
stomach, the stomach muscles begins to contract in the mid portion and then like all
peristaltic movement, they move towards the pylorus. Food is converted to chyme in
stomach. That is why food that is not properly mixed with gastric secretion cannot pass
through the pylorus. Once the constrictive wave reaches the pyloric sphincter, the properly
mixed food (chyme) is moved through the pyloric sphincter into the duodenum whereas
the ones that are not properly mixed are repelled back where it is mixed and then forced
back again by peristaltic move towards the pyloric sphincter. This process goes on and on
until the stomach is properly emptied.

22. As the stomach becomes progressively empty,
the peristaltic constrictive waves begin further up the stomach. This ensures that the
stomach is completely emptied of its contents.
The Peristaltic constrictive wave is due to the Basic Electrical Rhythm (BER) or due to
slow waves. The latter are not true action potential. They are slow undulating waves
unlike the resting membrane in smooth muscles. For GIT muscles, the resting membrane
potential is not a straight line. It controls the appearance of spikes. These spike are true
action potential and like AP elsewhere, it causes muscle construction.

23. The slow waves do not cause muscle
contraction in the GIT except in the stomach where it is strong enough to cause stomach
contraction.
• The rate of appearance of slow waves differ in different segments of the GIT. In the
stomach, it appears about 4 times per mins. In the duodenum, its about 12 times per
mins. In the ileum, its about 9 times per min. So this rate of appearance of slow waves
determine the rate of contractions of muscles of the segment.
NOTE ;The degree of fluidity of the chyme depends on
i. Quantity of food
ii. Amount of water
iii. Secretions
iv. Degree of digestion that has occurred.

24. STOMACH EMPTYING/SLOW EMPTYING
This enables the stomach to empty its contents at regulated intervals which ensure
optimal processing by the duodenum. It is promoted by intense peristaltic contractions in
the stomach antrum.it causes opening of the pyloric sphincter.The pylorus functions as a
pump that regulates the emptying of gastric content into the duodenum. This pumping
activity of the pylorus (pyloric pump) is regulated by both hormonal and neural factors
either from the stomach or from the small intestine.
GASTRIC FACTORS
They promote gastric emptying.
a. Increased food volume. This
is because of stretching of
the wall which elicits
myenteric reflexes that
stimulates peristalsis and
opening of the pylorus.
b.Gastrin hormone. It promotes
the activity of pyloric pump.

25. DUODENAL FACTORS
These factors are both neural and hormonal. The neural is due to Enterogastric
reflex. The Hormonal includes the (1) CholecystoKinin (CCK), (2)Secretin
and (3) VIP
All these hormones inhibit gastric motility and
emptying.
Secretin is secreted usually as a result of
presence of acid in the duodenum.
CCK is usually secreted in response to fatty
substance in the duodenum.
ENTEROGASTRIC REFLEX
When the volume of chyme in the duodenum is too much,signals are sent to
inhibit G.E thru
 Enteric nervous system
 Extrinsic nervous system
 Vagus nerve to the brain stem to inhibit excitatory signals to the stomach.
They inhibit emptying by reducing pyloric contractions and increasing the
tone of pylorus.
FACTORS THAT INITIATE ENTEROGASTRIC REFLEX
a. Degree of distension of duodenum
b. Degree of irritation
c. Acidity of chyme
d. Osmolarity

26. e. Presence of certain breakdown products eg protein and fat.

27. INTESTINAL MOTILITY
Small Intestine
There are two types of movement in the small intestine:
1. Mixing contractions
2. Propulsive movement
Mixing Movement
The mixing movement enables the intestinal contents to be mixed with intestinal
secretions. It is otherwise called Segmental movement. It also performs some degree of
propulsion. Presence of chyme in the S.I elicits stretching of the wall which causes
concentric contractions that divides the S.I into segments. The frequency of segmentation
contraction is determined by the frequency of electrical slow wave and it occurs regularly
in a rhythmic pattern.
 The propulsive movement is slow but can become very rapid in case of infection in
which case we have what is called PERISTALTIC RUSH .chyme is propelled
through the S.I by peristaltic wave which develops from any part of S.I then
goes towards the anus. This peristaltic wave is weak. There are also factors that
regulate small intestine motility and emptying .the regulators are also neural and
hormonal.

28. The neural is Gastroenteric reflex: it increases
motility and emptying of the small intestine. It is initiated by distension of stomach
which is conducted through myenteric plexus down the S.I.The hormonal factors
include those that increases motility and emptying and those that decreases motility
and emptying. Those that increases motility include; gastrin, CCK, Serotonin,
insulin.
Those that reduces motility include;Secretin, Glucagon.

29. ILEOCAECAL VALVE/SPHINCTER
Like all other sphincters, it only permits forward movement. There are factors that affect
the opening of the sphincter.
Factors that regulate Ileocaecal Valve.
Irritation of the distal ileum leads to opening of the sphincter so as to empty the ileal
contents.
Increased pressure in the caecum will inhibit the opening of the sphincter.
LARGE INTESTINE
There are 2 main fxns of the large intestine;
• Storage of faecal matter
• To absorb water and electrolytes.
•To absorb vitamins synthesized by colonic bacteria e.g Folic acid, Panthenoic acid,
Vitamin B6 and Vitamin K.

30. DEFAECATION
It is the process by which unwanted end products of digestion are sent out of the
body through the anus. There are 2 reflexes that govern defecation:
i. Intrinsic defaecation reflex
ii. Extrinsic defaecation reflex
The Intrinsic defecation is due to the intrinsic nervous system. It is usually weak
and it does not usually lead to satisfactory defecation.
To ensure satisfactory defecation,a more powerful defecation reflex is involved.
This is the Extrinsic Defecation reflex/parasympathetic defecation reflex. This
usually potentiates/enhances the intrinsic defecation reflex.

32. Defecation Reflex
Once the descending and sigmoid colon and the rectum is filled with faecal matter,
impulses are generated that are sent to the enteric (Myenteric) nervous system which
then sends appropriate signals to the descending colon, sigmoid and rectum causing
them to contract and free the faecal matter forwards, towards the anus. If the inner
sphincters are relaxed, faecal matter are sent out to the exterior. If the inner sphincters
are not relaxed, the faecal matter are retained in these areas (rectum).

33. The extrinsic defecation reflex comes into play when
the signals are sent to the sacral segment of the spinal cord which then sends
appropriate messages to the descending colon, sigmoid and the rectum to cause a more
forceful contraction that propels the faecal matter forward to the anus.
In addition to these events, there are certain other
behavioural responses that are associated with successful defaecation. These include:-
Deep breath
Glottic closure: This ensures increase of the intraabdominal pressure.
Contraction of diaphragm and Abdominal muscles: This creates additional force that
pushes the faecal matter towards the anus.

34. THE END