Week 2.1 - Gastric Secretion Flashcards
What is the function of the fundus?
mostly gas and for storage
What is the function of the stomach body? (5)
- storage
- pepsinogen
- mucus
- HCl
- intrinsic factor
What is the function of the Antrum?
grinding food and contains G cells which secrete gastrin
What are the components of gastric glands?
mucous neck cells, chief cells and parietal cells
What is the function of the chief cells?
secrete pepsinogen which is inactive pepsin
What is the function of the parietal cells?
secretes HCl and intrinsic factor
What does it mean that the stomach epithelium is polarised?
It has many proteins and many functions
What is the process of HCL formation?
- CO2 in blood diffuses into parietal cells.
- combines with water to form carbonic acid, with carbonic anhydrase enzyme
- H2CO3 dissociates quickly into H+ and HCO3-
- H+ exits via H+K+ ATPase - 1 in 1 out. makes lumen more acidic
- HCO3- bicarbonate exits cell, making blood more basic. exchanges with Cl-
- Cl- exits via channel and takes water into lumen. binds with H+ forming HCl
What is the name of the process that causes blood to become more basic after eating?
postprandial alkalinisation. becomes slightly above 7.4
What is the pH in the stomach lumen vs the blood?
1.5 in lumen and 7.4 in blood
How do we control release of HCl?
controlling kinase activation in the parietal cells
How is H+ released from parietal cells?
hydrogen potassium pump needs to be phorphorylated to work. its phosphorylated by active protein kinase enzyme. certain factors can activate PK
Which factors activate PK and which inhibit it?
gastrin, ACh and histamines activate it.
prostaglandins inhibit it
How does gastrin control HCl production?
- G cells in antrum release gastrin hormone.
- goes via blood to parietal cell.
- binds to CCKB receptor.
- releases calcium into cell which activates PKC
How does histamine control HCl production?
- acts on H2 receptor which couples to G receptor
- releases adenyl cyclase which converts ATP to cAMP
- Activates PKA
