Gastric Secretion Flashcards
What are some areas of the stomachs anatomy?
Fundus
Body
Antrum
Pyloris region
What is the function of the fundus of the stomach?
Storage
What are the functions of the body of the stomach?
Storage
Mucus protects stomach surface
Produce hydrochloric acid
Pepsinogen production
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)
Gastrin production
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?
Body
Where in the stomach is pepsinogen secreted?
Body
Where in the stomach is gastrin secreted?
Antrum
What is found in gastric pits?
Surface mucous cells
What area is deep to the gastric pit?
Gastric gland
What cells make up the gastric gland?
Mucous neck cell
Parietal cell
Chief cell
What do mucous neck cells secreted?
Mucus
What do chief cells secreted?
Pepsinogen
What do parietal cells secrete?
Hydrochloric acid
Intrinsic factor
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?
7.4
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?
Carbonic anhydrase
What are examples of things that activates the K/K ATPase pump?
Histamine
Acetylcholine
Gastrin