Gastric secretion Flashcards
What is the function of the Fundus of the stomach?
Storage
- Rugae make it stretchy so it can accomodate stuff
What are the functions of the body of the stomach?
- Storage
Secretion of:
- Mucus
- HCl
- Pepsinogen
- Intrinsic factor
What are the functions of the antrum of the stoamach?
Mixing / grinding
Gastrin secretion
What cells are in gastric pits and glands in the stomach?
Surface mucous cells
Mucous neck cells
Parietal cells
Chief cells
G cells
<em>There are some other spicy types like ECL cells but these are the main ones</em>
![](https://s3.amazonaws.com/brainscape-prod/system/cm/289/602/413/a_image_thumb.png?1570622945)
What do mucus neck cells do?
Mucous and Bicarbonate secreting cells found in gastric glands
They eventually mature, move up to the surface epithelium and become surface mucous cells
What do chief cells do?
Secrete Pepsinogen
Found at the bottom of gastric glands
What is pepsinogen?
Inactive precursor to pepsin, which is an enzyme that digests proteins
It is converted to active pepsin by gastric acid (ie in acidic conditions pH < 3)
What do parietal cells do?
Secrete HCl and intrinsic factor
They also have a bunch of receptors to control their secretion
These cells are found in the gastric glands
What is intrinsic factor?
Glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B12 later on in the ileum of the small intestine
How is Gastric acid (HCl) secreted from parietal cells into the stomach lumen?
- CO2 and H2O in cytoplasm forms carbonic acid (H2CO3)
- Carbonic acid –> Bicarbonate (HCO3-) + H+
- Bicarbonate removed to blood by transporter in exchange for Cl- ion
- Transporter yeets out the H+ into the lumen in exchange for a K+
- Cl- moves into lumen through a Cl- channel
![](https://s3.amazonaws.com/brainscape-prod/system/cm/289/602/786/a_image_thumb.png?1570623846)
What enzyme allows conversion of Carbonic acid to bicarb and H+?
Carbonic anhydrase
What chemicals control the level of HCl secretion?
Gastrin - stimulates
Histamine - stimulates
Acetylcholine - stimulates
Prostaglandin - inhibits
How does Gastrin control HCl secretion from parietal cells?
- Gastrin in blood binds to parietal cell’s membrane receptors
- Receptor releases intracellular Ca2+
- Ca2+ activates protein kinases
- Induces H+K+ATPase initiating HCl secretion
![](https://s3.amazonaws.com/brainscape-prod/system/cm/289/603/886/a_image_thumb.png?1571067803)
How does Histamine control HCl secretion by parietal cells?
- Histamine in blood binds to H2 receptor on P cell membrane
- Receptor activates G coupled (Gs) protein
- Gs protein activates adenylyl cyclase
- Adenylyl cyclase converts ATP to cAMP
- cAMP activates protein kinases
- Protein kinases stimulates H+K+ATPase which starts chucking out H+
![](https://s3.amazonaws.com/brainscape-prod/system/cm/289/604/185/a_image_thumb.png?1571067873)
How does acetylcholine increase HCl secretion?
- Binds to receptor on parietal cell
- Secretes intracellular Ca2+
- Acts on protein kinase
- Induces H+K+ATPase
(same as gastrin)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/289/604/470/a_image_thumb.png?1571067888)