Gastric barrier, gastric secretion Flashcards
The production of high concentration of hydrogen in gastric juices also requires _________.
backlift of hydrogen into the mucosa
What prevents the backlift of acid secretion into mucosa?
Gastric barrier
What is an acid barrier made of?
alkaline mucus
tight junctions between epithelial cells
The gastric acid barrier may be damaged by?
Toxic substances (Alcohol, aspirin, NSAIDs)
When the gastric barrier is damaged, what will happen?
secreted acid leaks down an electrochemical gradient into the mucosa causing mucosal damage
[Acid that is secreted leaks into the mucosa, leading to damage due to an electrochemical gradient.]
Three primary stimuli in gastric acid secretion
Gastrin
Histamine
Acetylcholine
Hormone released by G-cells
Gastrin
Gastrin is released in response to:
- GRP
- Presence of oligopeptides in gastric lumen
Gastrin is carried through the bloodstream to the ____________.
fundic glands
Gastrin binds to parietal and chief cells to ___________________.
activate secretion
Gastrin binds to ECL to ________________.
release histamine
This hormone is released from enteric nerve endings in the fundus
Acetylcholine
What can Acetylcholine stimulate?
Pepsinogen, HCl, and mucus
CAN parietal and chief cell
Gastrin and Histamine strongly stimulate ______________.
acid secretion
Gastrin and Acetylcholine promote secretion by _______________.
elevating cytosol calcium
Gastrin, histamine, and acetylcholine bind to distinct receptors on _______________.
basolateral membrane
Histamine promotes secretion by ___________.
Increasing cAMP
This pathway means small changes in stimuli can result in high secretion
synergistic pathway
Therapeutically, secretions can be inhibited by?
blocking one trigger
an example of widely used therapies
histamine 2 antagonist
These are produced by chief cells
pepsinogen and lipase
This has no digestive activity but becomes activated in response to contact with a certain enzyme.
Pepsinogen is inactive but is activated in contact with HCl
The active form of pepsinogen
Pepsin
Pepsin functions as
a proteolytic enzyme that initiates protein digestion
optimum acidity of pepsin
pH of 1.8 to 3.5
pepsin is inactive at the pH level of what?
pH >5
Stimulation of pepsinogen secretion occurs in response to what?
Acetylcholine from vagus nerve
Pepsinogen is heavily influenced by _______.
amount of acid
These are produced by parietal cells along with HCl
Intrinsic factor
Intrinsic factor is essential for the absorption of?
Vitamin B12 in ileum
What is destructed in chronic gastritis?
parietal cells destruction
What is developed in chronic gastritis?
achlorhydria
pernicious anemia
What is the reason for pernicious anemia?
failure of RBC to mature due to Vitamin B12 absence
