This document summarizes gastric motility and emptying. It discusses three motor functions of the stomach: storage of food, mixing food with gastric secretions to form chyme, and slow emptying of chyme into the small intestine. The stomach has three regions (fundus, body, antrum) that work together for these functions. Food first causes the fundus to relax for storage via vagal reflexes. Then the antrum contracts to mix food via slow waves and peristalsis. Finally, the antrum contracts to empty chyme at a controlled rate depending on factors like food content and duodenal pH via neural and hormonal regulation.

1. GASTRIC
MOTILITY &
EMPTYING
By Dr S B Phiri
Dr Phiri S B

2. Objectives
At the end, learner must be able to………
 Gastric motility and emptying
 Regulation of Gastric motility and emptying
Dr Phiri S B

3. Motor functions of the stomach
The motor functions of the stomach are
threefold;
1. Storage of large quantities of food until the
food can be processed in the duodenum and
lower intestinal tract.
2. Mixing of this food with gastric secretions until
it forms a semifluid mixture called chyme, and
3. slow emptying of the chyme from the
stomach into the small intestine at a rate
suitable for proper digestion and
absorption by the small intestine.
Dr Phiri S B

4. Introduction
 Food from the esophagus is stored in the stomach;
thus its’ a reservoir.
 Then mixed with acid, mucus, and pepsin; and
released at a controlled, steady rate into the
duodenum.
 Both peristaltic and segmental contractions occur in
the stomach.
 Regulation is achieved through intergration of neural
reflexes and hormonal influences mediated via entericDr Phiri S B

5. Gastric motility and emptying
 The stomach has three anatomic divisions—the
fundus, body, and antrum.
 The orad region of the stomach includes LES, the
fundus and the proximal body; contains oxyntic
glands and is responsible for receiving the ingested
meal.
 The caudad region of the stomach includes the
antrum, distal body and pyloric sphincter;
responsible for the contractions that mix food and
propel it into the duodenum.
Dr Phiri S B

6. 1. Receptive relaxation
• A vagovagal reflex that is initiated by distention of
the stomach and is abolished by vagotomy.
 The orad region of the stomach relaxes to
accommodate the ingested meal.
 Mediated by vagal afferents stimulation and
movement of the pharynx and esophagus.
 CCK participates in "receptive relaxation" by
increasing the distensibility of the orad stomach...ie
inhibits gastric motility.
Dr Phiri S B

7. 2. Mixing movements
• The caudad region of the stomach contracts to mix
the food with gastric secretions and begins the
process of digestion and the size of food particles
is reduced.
 Slow waves , initiated by Interstitial cells of Cajal in
the caudad stomach occur at a frequency of 3-4
waves/min. They depolarize the smooth muscle
cells.
 If threshold is reached during the slow waves,
action potentials are fired, followed by contraction.
 The frequency of slow waves sets the maximal
 A wave of contraction closes the distal antrum.
Thus, as the caudad stomach contracts, food is
propelled back into the stomach to be mixed
(retropulsion).
 Gastric contractions are increased by vagal
stimulation and decreased by sympathetic
stimulation.
 Even during fasting, contractions (the "migrating
myoelectriccomplex") occur at 90-minute intervals
and clear the stomach of residual food. Motilin is
the mediator of these contractionsDr Phiri S B

8. 3. Gastric emptying and regulation
 The caudad region of the stomach contracts to propel food into the
duodenum.
 The rate of gastric emptying depends on
1. Isotonicity or osmolality of the stomach contents.
 If the stomach contents are hypertonic or hypotonic, gastric
emptying is slowed via a negative feedback ie enterogastric
feedback mechanism.
2. Type of food ingested.
• Food rich in carbohydrate leaves the stomach in a few hours.
Protein-rich food leaves more slowly, and emptying is slowest after
a meal containing fat
 Fat inhibits gastric emptying (i.e., increases gastric emptying time)
by stimulating the release of CCK. (Enterogastrone feedback)
3. H+ in the duodenum; inhibits gastric emptying via direct neural
reflexes. H+ receptors in the duodenum relay information to the
gastric smooth muscle via interneurons in the GI plexuses.Dr Phiri S B

9. Regulation of Gastric motility and
Emptying
 2 mechanisms inhibit gastric motility, secretion
and duodenal filling:
1. Neural enterogastric reflex
2. Hormonal (enterogastrone) mechanisms.
Dr Phiri S B

10. The end
DR S B PHIRI