What are some areas of the stomachs anatomy?
What is the function of the fundus of the stomach?
What are the functions of the body of the stomach?
Mucus protects stomach surface
Produce hydrochloric acid
Intrinsic factor production
What is the function of mucus in the stomach?
Protect the surface of the stomach
What causes the low pH of the stomach?
Presence of hydrochloric acid
Why is pepsinogen in the stomach and not pepsin?
Active pepsin would digest the stomach itself as it is made of proteins
What is the function of intrinsic factor?
Required for vitamin B12 absorption
What are the functions of the antrum?
Mixing/grinding (mix secretions with content of diet and grind them down)
What is the function of gastrin?
Enter circulation system (is a hormone) and come back to the body of the stomach where it switches on hydrochloric acid and pepsinogen secretion
Where in the stomach is hydrochloric acid secreted?
Where in the stomach is pepsinogen secreted?
Where in the stomach is gastrin secreted?
What is found in gastric pits?
Surface mucous cells
What area is deep to the gastric pit?
What cells make up the gastric gland?
Mucous neck cell
What do mucous neck cells secreted?
What do chief cells secreted?
What do parietal cells secrete?
Why are surface mucous cells found superficial to the gastric gland?
To protect us from the secretions of the gastric gland
What happens do mucous neck cells once they mature?
They become surface mucous cells
What is the pH of blood?
What is the mechanism of parietal cell secretions?
1) Carbon dioxide is present in the blood which diffuses across the cell membrane into cell
2) CO2 combines with H2O in the cytoplasm which is controlled by enzyme carbonic anhydrase
3) Forms unstable H2CO3 which dissociates into H+ and HCO3 (bicarbonate)
4) H+ ion pumped by H/K ATPase up to its concentration gradient out of the cell while K is pumped in (1:1 ratio)
5) Bicarbonate is transferred out of the cell at baseolateral membrane for Cl
6) Cl exits alongside H+ ion into stomach lumen
7) Osmotic gradient due to H+ and Cl leaving the cell causes water to transfer across from the blood into the stomach
8) pH of stomach is less than 2 because of hydrogen ions being pumped into stomach
9) Because bicarbonate transferred out into blood the pH increases a bit over 7.4
What pump causes the stomach pH to be less than 2?
H/K ATPase pumping H+ into the stomach lumen
What enzyme allows CO2 to combine with H2O?
What are examples of things that activates the K/K ATPase pump?
What is an example of something that inhibits the H/K ATPase pump?
What is the mechanism of gastrin activating the H/K ATPase pump?
1) Gastrin binds with receptor on parietal cell that is coupled up to a system that increases intracellular Ca2+
2) Ca2+ acts on protein kinases to switch on H/K ATPase causing more hydrogen to be pumped into the stomach
What is the mechanism of histamine activating the H/K ATPase pump?
1) Histamine acts on receptor on parietal cell (unique histamine receptor for stomach, type 2 receptor whereas everywhere else is type 1)
2) Coupled with Gs that act on AC causing the conversion of ATP to cAMP
3) cAMP acts on protein kinases that turn on H/K ATPase pump
What is the mechanism of acetylcholine activating the H/K ATPase pump?
1) Acts on muscurinic cholinergic receptor that is coupled up to a system that increases Ca2+ intracellular levels
2) Ca2+ acts on protein kinases that turn on H/K ATPase pump
What is the mechanism of prostaglandins inhibiting the H/K ATPase pump?
1) Acts on receptor that is bound to inhibitor protein Gi
2) Inhibits conversion of ATP to cAMP
3) So reduces activation of protein kinases and turns off H/K ATPase pump