Gastric secretion Flashcards
What is the main function of the fundus of the stomach?
Storage
What are the functions of the body of the stomach?
Storage
Mucus
GCL
Pepsinogen
Intrinsic factor
What are the functions of the antrum of the stomach?
Mixing/grinding
Gastrin
What do mucous neck cells of gastric glands secrete?
Mucus
What do chief cells of gastric glands secrete?
Pepsinogens
What do parietal cells of gastric glands secrete?
HCl (hydrochloric acid)
Intrinsic factor
What does hydrochloric acid (HCL) do in the stomach?
Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids
- This is known as proteolysis.
What pH is the stomach lumen?
pH < 2
What is the normal pH of blood?
Around 7.4
What 3 mechanisms is gastric acid secretion controlled by?
Neurocrine (vagus/local reflexes)
Endocrine (gastrin)
Paracrine (histamine)
What are different mechanisms stimulating gastric acid secretion (Cephalic phase)?
Sight, smell, taste of food > increased vagus nerve activity > +acetylcholine > Parietal cells
Sight, smell, taste of food > Increased vagus nerve activity > G cells > +Gastrin > Parietal cells
Gastrin/ACh > ECL cells > +Histamine > Parietal cells
What are the different mechanisms of the gastric phase?
Distension of stomach (arrival of food) > Vagal/enteric reflexes > +ACh > Parietal cells
Peptides in lumen > G cells > +Gastrin > Parietal cells
Gastrin/ACh > ECL cells > +Histamine > Parietal cells
What is a mechanism inhibiting gastric acid secretion during the Cephalic phase?
Stopping eating > Decreased vagal activity
What is a mechanism inhibiting gastric acid secretion during the Gastric phase?
Decreased pH (increased HCl) > Decreased gastrin
What are mechanisms inhibiting gastric acid secretion during the intestinal phase?
Acid in duodenum > enterogastric (splanchnic) reflex > decreased gastrin stimulation of parietal cells
Fat/CHO in duodenum > GIP release > decreased gastrin secretion > decreased parietal HCl secretion
What are enterogastrones?
Hormones released from gland cells in duodenal mucosa
- Secretin, cholecystokinin (CCK), GIP
When are enterogastrones released?
Released in response to acid, hypertonic solutions, fatty acids or monoglycerides in duodenum
- They act collectively to prevent further acid build up in duodenum
What are the 2 strategies enterogastrones use to prevent further acid build up in duodenum?
- Inhibit gastric acid secretion
2. Reduce gastric emptying (inhibit motility/contract pyloric sphincter)
What is pepsinogen?
A substance which is secreted by the stomach wall and converted into the enzyme pepsin by gastric acid
What cells secrete pepsinogen/
Chief cells
When is pepsin activated?
Low pH < 3
Pepsinogen > Pepsin
What happens to pepsins at neutral pH?
It is inactivated
What is gastric mucus produced by?
It is produced by surface epithelial cells and mucus neck cells
What is the role of gastric mucus?
Protects mucosal surface from mechanical injury
Neutral pH (HCO3) > protects against gastric acid corrosion and pepsin digestion
