Gastric Secretion Flashcards
Whats the function of the fundus?
Storage, its got a lot very stretchy rugae
What are the functions of the stomach body?
- Storage
production of: - Mucous
- Gastric acid (HCl)
- Pepsinogen
- Intrinsic factor
What does Gastric acid do?
Begins protein digestion by acid hydrolysis and sterilizes food.
What can survive gastric acid?
Only Heliobacter Pylori can survive stomach acid
How does pepsinogen become pepsin and what does it do?
Pepsinogen is activated (converted to pepsin) by gastric acid.
Its a protease.
Whats the function of the antrum of the stomach?
- Mixing an Grinding stomach contents
- Gastrin production
What does gastrin do?
Its a peptide hormone that stimulates gastric acid production
What kind of cells are in a gastric gland and what do they produce?
Mucous neck cells -> mucous
Chief Cells -> Pepsinogens
Parietal Cells -> HCl & Intrinsic factor (contains receptors for the various chemicals that affect HCl secretion)
How is Gastric acid secreted from the epithelium?
1) CO2 from blood + water in the epithelial cell froms carbonic acid
2) degrades to bicarbonate and H+
3) Cl- enters the cell swapping with bicarbonate
4) Cl- exits into the stomach through a Cl- channel
5) the H+ from the carbonic acid is pumped into the stomach in exchange for K+ 1 for 1
How does the blood pH change after a meal and why?
Transient alkalisation due to the bicarbonate being pumped into the blood from the stomach epithelium in exchange for Cl- ions.
Part of gastric acid secretion
Does gastric acid secretion happen all the time?
No only when eating as its a high energy process
What 4 chemicals control the gastric acid secretion? Which are stimulatory and which are inhibitory?
What cell type do they act on to affect HCl secretion?
Stimulatory:
- Gastrin
- Histamine
- Acetylcholine
Inhibitory:
- Prostoglandin
They bind to receptors on parietal cells in the stomach epithelium
How does Gastrin affect HCl secretion in the stomach?
Gastrin:
-> Binds to receptor on epithelial cell
-> Receptor releases intracellular Ca2+
-> Ca2+ activates protein kinases
-> Induces H+K+ATPase initiating HCl secretion
How does histamine affect Gastric acid secretion?
The stomach has a unique histamine receptor (H2).
-> Binds to H2
-> Activates a g coupled protein (Gs)
-> Converts ATP to cAMP
-> Acts on protein Kinase
-> Stimulates HKATPase
How does acetylcholine affect HCl secretion?
-> Binds to receptor on parietal cell
-> Secretes intracellular Ca2+
-> Acts on protein kinase
-> Induces H+K+ATPase