GI Gastric Morility And Gastric Acid Secretion Flashcards
What is the stand the starting point for
Digestion of proteins (via pepsin and HCl)
What does the stomach do
Mixes the food with gastric secretions to products chyme
What is the absorption like in the stomach
Limited amount
How much gastric juice is approx prod by stomach a day
2litre/day
What are the structural elements that make up the j shaped bag stomach
Fundus Cardia Body Rugae Pylorus Antrim Lesser and greater curvature
What so the mixing like in the stomach
Direction of peristaltic move from funds to pylorus forces food to sphincter
If sphincter open this is emptying to duo
If closed retropulsion of chyme allowing mix
What determines the escape of chyme through the pyloric sphincter
The strength of the Antral wave
What is the strength of the Antral wave governed by
Gastric factors originating in stomach
Duodenal factors originating in duo
What are the gastric factors influencing gastric emptying
Rate of emptying proportional to volume of chyme in stomach
- as vol increases the greater distension of wall of stomach
Consistency of chyme
- rotting facilitated by finely divided thick liquid chyme so can fit through pyloric sphincter
What are the duodenal factors which influence gastric emptying
Duodenum must be ready to receive chyme and can delay this emptying
Stimuli which duodenum drives the neuronal and hormonal responses
How can the duo delay the stomach emptying
Neuronal - enterogastric reflex, when duo senses chyme sends signal to decrease Antral peristalsis via intrinsic nerve plexuses and autonomic neurones
Homonal - release enterogastrones( secretin, cck) from endocrine cells in duo inhibit stomach contraction thoug GPCR’s
How does fat influence the duodenal hormonal and neural responses
Potent delay in emptying required for digestion and abs in small intestine
Difficult to digest as insol water
Digested v slow
Howes acid affect the duodenal hormonal and neuronal repsonse
Only small mount added
Time required for neutralisation by bicarbonate sec from pancreas
How does hyper tonicity affect the hormonal and neuronal factors of the duo
Products of carb and protein digestion are osmotically active and draw water into small intestine
Danger of reduced plasma vol and circulatory disturbances
What does a g cell in the gastric pit release
Gastrin
What’s does a d cell in a gastric pit release
Somatostatin.
What does a parietal cell release
HCl and intrinsic factor
What does an enterochromaffinlike cell prod
Histamine
What does a chief cell produce
Pepsinogen
What are the two oes of gastric pits and where are they found
Pyloric gland area in the Antrum
Oxcyntic mucosa in the fungus and body
What fuels are found in the pyloric gland area pastric pit
D cells and g cells
What cell homes are found in the oxcyntic mucosa gastric pits
Parietal
Enterochromaffinlike cell
Chief cell
What does an oxcyntic gland produce
HCl Pepsinogen Histamine Mucus Intrinsic factor
What does a pyloric area gland produce
Gastrin
Somatostatin
Mucus
He hat does HCl from the oxcyntic mucosagastric pit do
Activates pepsinogen to pepsin for proetin digestion
Denatures protein breaks tertiary and secondary structures
Kills most micor ORGS ingested in food
What does pepsinogen from the oxcyntic do
Inactive preserver for pepsin for protein digestion
What does intrinsic factor from oxcyntic do
Binds vit b12 allowing abs in terminal ileum only thing essential for life
What does the histamine and mucus do form the oxcyntic do
Histamine - stim HCl sec
Mucus - protective pord in gastric pits and epi, stops apical attack of epi cells
What does gastrindo form the pyloric do
Stimulate HCl sec
What’s does somatostatin do form pyloric
inhibits HCl sec between meals
Counter regulation to Gastrin
What is the resting state of the parietal cell
Hydrogen and pottasium ATPase largely in cyto tubulovesicles
What so the stim state of the parietal cell
Hydrogen and pottasium ATPase traffics to apical mem taking residence in extended Microvilli
What are the 3 phases of gastric sec
Cephalic
Gastric
Intestinal
What is the cephalic phase of gastric sec
Before foods reaches stomach, anticipatory phase causes increases parasymp flow to stomach and sec acid to prep for digestion of meal
What is the gastric phase of gastric secs
When food is In the stomach
What is the intestinal phase of gastric sec
After food left stomach chyme acid sec off
Includes factors from small intestine
What does muscarinic receptor antagonists do and an example
Block acid sec competitively
What does h2 histamine receptor antagonists do and an example
Block acid sec competitively
Ranitidine
What do proton pump inhibitors do and an example
Block acid sec by covalent modification
Omeprazole
What do non steroidal anti inflammatory drugs do and an examole
Block acid sec irreversibly
Aspirin
What protects the mucosa form HCl attack and pepsin
Locally produced prostaglandins.
What do locally produced prostaglandins do
Reduce acid sec
Increase mucus and bicarbonate sec
Increase mucosal blood flow
What is a peptic ulcer
Any ulcer in an area where the mucosa is exposed to HCl and pepsin (stomach, duo)
What so th development of a peptic ulcer associated with
A shift in balance between mucosal damaging and mucosal protecting mechanisms
What do NSAIDs do
Reduce prostaglandin formations - COX1 Inhibition which may trigger
Gastric ulceration
Bleeding
How can longer term gastric damage due to NSAIDs be treated
With pge1 analogue misoprostol
Inhib basal and food stim gastric acid formation
Maintains secretion of mucus and bicarbonate
Compensates for loss prostaglandins when cox1 inhib
What is the origination of a peptic ulcer form
Imp factor H.pylori motile bacteria which burrows into mucosal barrier where it is protected by gel but caused inflammation and breakdown mucosal barrier expo the mucosal mem to HCl and pepsin
What do drugs used to treat peptic ulcers aim to do
Decrease acid sec.
Increasing mucosl resistance
Eradicating h pylori
What are drugs used to reduce gastric acid used for
Peptic ulcers
Gastric oesophageal reflux disease
Acid hypersecrtion
What are mechanisms of antisec activity
Inhibition of proton pump
Competitive antagonisms if histamine h2 receptors
Competion antagonism of muscarinic m1 and m2 ACh receps
Antagonism of Gastrin receps
What is the stomach driven by (nerve)
Vagus
