Gastric secretion

1. Gastric secretions -2
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
RDGMC
DR Sai Sailesh Kumar G 1

2. Learning objectives
 List the different types of gastric glands and
indicate their secretions
 List the composition and functions of gastric juice
 Outline the steps involved in the formation of
gastric acid
 Describe the regulation of gastric acid secretion
 List different phases of gastric acid secretion and
factors influencing them
 Outline the basis of various forms of treatment for
acid peptic disease DR Sai Sailesh Kumar G 2

3. Phases of Gastric secretion
 Gastric secretion occurs in three phases
1. Cephalic phase
2. Gastric phase
3. Intestinal phase
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4. Cephalic Phases
 Occurs even before food enters stomach
 Especially while it is being eaten
 It results from sight, smell, thought or taste of
food
 Greater the appetite, more intense is stimulation
 This phase of secretion normally accounts for
about 30% of gastric secretion associated with
eating a meal
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5. Regulation of Cephalic Phases
 Neurogenic signals that cause the cephalic
phase originates in
1. Cerebral cortex
2. Appetite centers of amygdala
3. hypothalamus
 Signals transmitted through dorsal motor
nucleus of vagus
 Then through vagus nerve to stomach
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6. Regulation of Cephalic Phases
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7. Sham feeding
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8. Sham feeding
 In classic “sham” feeding studies performed on
dogs equipped with an oesophageal stoma and a
gastric fistula, Pavlov demonstrated that food
was a prompt and powerful stimulant of gastric
secretion.
 This stimulation occurred despite the fact that
the ingested food entered the dog's mouth and
pharynx and exited through the stoma, never
actually reaching the stomach
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9. Gastric Phases
 Occurs once food enters stomach
 Causes secretion of gastric juice during several
hours while food remains in the stomach
 This phase of secretion normally accounts for
about 60% of gastric secretion associated with
eating a meal
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10. Regulation of Gastric Phases
 This phase is regulated by
1. Long vago vagal reflex from stomach to brain
and back to stomach
2. Local enteric reflexes
3. Gastrin- histamine mechanism
 Signals transmitted through dorsal motor
nucleus of vagus
 Then through vagus nerve to stomach
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11. Intestinal Phases
 Occurs when food enters upper portion of small
intestine
 Particularly in the duodenum
 Small amounts of gastric juice secreted
 This phase of secretion normally accounts for
about 10% of gastric secretion associated with
eating a meal
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12. Regulation of intestinal Phases
 This phase is regulated by
1. Nervous mechanisms
2. Hormonal mechanisms – probably partly
because of small amounts of gastrin released
by duodenal mucosa
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13. inhibition of gastric secretion
 Intestinal chyme slightly stimulates the gastric secretion
during the early intestinal phase
 It paradoxically inhibits gastric acid secretion at other
times
 This inhibition results from
1. Presence of food in the small intestine initiates a
reverse entero gastric reflex
2. Transmitted through myentric nervous system,
sympathetic and vagus nerves that inhibits gastric
secretion
3. Secretin, gastric inhibitory peptide, vasoactive
intestinal poly peptide and somatostatin
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14. Why inhibition?
 The inhibitory factors inhibits gastric secretion
and motility
 To slow passage of chyme from stomach to
intestine
 Which is already filled or already over active
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15. Gastric secretion during inter
digestive period
 Inter digestive period – when little or no
digestion occurring anywhere in the gut
 Stomach secretes few milliliters of gastric juice
each hour
 Non oxyntic type of secretion
 Mainly mucus little pepsinogen and no acid
 Emotional factors may increase the secretion to
50 ml or more
 May leads to peptic ulcer
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16. Secretion and activation of
pepsinogen
 Several types of pepsinogen secreted
 Basic function is same for all types
 Pepsinogen has no digestive activity
 When it comes in contact with HCL, it become
activated and become pepsin
 Pepsin is a active proteolytic enzyme in highly
acidic medium
 HCL is necessary for its action
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17. Regulation of pepsinogen
secretion
 Acetyl choline – released from vagus or from
gastric enteric nervous plexus
 Acid in the stomach
 Acid may not directly stimulate peptic cells
 Acid elicit local reflexes that stimulates peptic
cells
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18. Secretion of intrinsic factor
 Essential for absorption of vitamin B12 in ileum
 Secreted by parietal cells
 When parietal cells destroyed
 Occurs in person with chronic gastritis
 Achlorhydria – lack of acid secretion
 Perniciuos anemia – lack of RBC maturation
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19. GIT hormones
 GIT is considered as one of the largest endocrine
glands
 Around 30 peptide hormone genes are found
 Some important hormones
1. Gastrin
2. Secretin
3. Cholecystokinin
4. Gastric inhibitory peptide
5. Motillin
6. Peptide YY
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20. Gastrin
 Secreted by: G cells in the antrum of stomach
and duodenum
 Primary stimulus: stretch, peptides and amino
acids, vagus
 Functions
1. Increases gastric HCL
2. Increase in gastric mixing
3. Increase in lower GIT motility
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21. Secretin
 Secreted by: S cells of duodenum
 Primary stimulus: Acidic chyme
 Functions
1. Increases pancreatic buffer secretion
2. Increase in biliary and small intestine buffer
secretion
3. Decrease in gastric motility
4. Decrease in gastric HCL
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22. CCK
 Secreted by: I cells of duodenum and jejunum
 Primary stimulus: Small peptides, amino acids and
fats
 Functions
1. Increases pancreatic enzyme secretion
2. Increase in pancreatic and biliary buffer secretion
3. Contraction of gall bladder
4. Relaxation of sphincter of oddi
5. Decrease gastric emptying
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23. Gastric inhibitory peptide
 Secreted by: Duodenum and jejunum
 Primary stimulus: Fatty acids, amino acids and
glucose
 Functions
1. Decreases gastric HCL secretion
2. Increase in pancreatic insulin secretion
3. Decrease gastric emptying
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24. Peptic ulcer
 Excoriated area of stomach or intestinal mucosa
 Primary cause:
1. Digestive action of gastric juice
2. Or upper small intestine secretion
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25. Peptic ulcer
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26. Basic cause
 Imbalance between the rate of secretion of
gastric juice and degree of protection offered by
1. Gastroduodenal mucosal barrier
2. Neutralization of gastric acid by duodenal
juices
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27. Specific causes
 Helicobacter pylori infection
1. Break down of Gastroduodenal mucosal barrier
2. Stimulation of gastric acid secretion
3. About 75% of cases are due to this bacterial
infection
4. This infection last life time unless eradicated by
anti bacterial therapy
5. This bacteria can penetrate the gastric mucosal
barrier
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28. Other causes
 Smoking – increases nervous stimulation of
stomach secretory glands
 Consumption of alcohol – breakdown mucosal
barrier
 Consuming asprin and other NSAIDs –
breakdown of mucosal barrier
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29. Treatment
1. Use of antibiotics along with other agents to kill
infectious bacteria
2. Administration of gastric suppresant drugs
 Ranitidine – antihistaminic agent – blocks stimulatory
effect of histamine on gastric glands (histamine 2
receptors)
 Omeprazole – proton pump inhibitors
1. Neutralize the gastric acids with antacids
2. Use of bismuth products that enhances mucosal barrier
3. Quitting smoking, alcohol consumption
4. Stress management
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30. DR Sai Sailesh Kumar G 30

31. THANK YOU
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