Gastic secretion Flashcards
How does the stomach participate in protein digestion>
acid hydrolysis and pepsin cleavage
How does the contents from the stomach enter the SI?
at a controlled rate to optizmize further digestion and absoprtion
Bezoar
ball of foreign material trapped in stomach (hairball)
Emesis
Vomiting, forcible ejection of stomach contents through the mouth
Dyspepsia
indigestion, pain in upper abdomen after eating
Gastroparesis
delayed emptying
Migrating Motor Complex
clears undigested material from the GI tract
Regurgitation
flow of material that has not reached the stomach back up the esophagus
Rugae
Stomach folds which expand as stomach fills
Scintigraphy
using a dual-radiolabeled solid and nutrient liquid meal, to measure gastric emptying
Trituration
grinding of food into small molecules
Paritel cell secretes
HCL, IF (for B12 absoprtion in the ileum)
Chief cells secrete
pepsinogen for protien digestion
surface mucous cells secrete
mucus, HCO3 fir gastroprotection
G cells in the antrum secrets
gastrin which activate parietall cells in the fundus to secrete acid
What kind of receptor does gastrin bind to
CCK2
what triggers gastrin release from the g cells in teh antrum?
seeing food or stomach distention causes vagal stimulation, causing gastrin releasing peptide, aromatic AA in the lumen
What activates parietal cells?
gastrin, histamine, and AcH
What activates ECL cells?
AcH, gastrin
ECL cells release what?
histamine which then binds to parietal cells
What happens upon parietal stimulation?
tubulovesicular membranes fuse with canalicular membranes increasing the density of H+, K+ ATPase molecules at the apical membrane.
Describe the ion transport of the parietal cells
Protons are made in the cytosol and pumped out via - H+, K+ ATPase into the lumen, bicarb in exported in from the basolateral (blood) side by vesiscular fusion/CH/HCO3 exchanger and enters blood stream
How does Cl move during parietal cell stimulation>
passive from basolateral side to lumen, water follows
What is the electrical potential exists across the gastric mucosa at rest? during activation?
-70, -30
What inhibits gastrin release?
somatostatin which is secreted from D cells in the atrum when the pH is <3
What happens during the gastric phase?
You get an icnrease in pH due to food which decreases somatosatin secretion
what does somatisatin inhibit?
Inhibits formation of cAMP(prostiglandins also do this) via a Gi-dependent signaling pathway in parietal cells,
indirectly inhibits ECL secretion of histamine,
G cells release of gastrin
What does the feedback from the duodenum do to parietal cells
nervous reflux blocks activation of parietal cells, enterogastrones like secretin block secretion of histamine by ECL cells
What is the Interdigestive Phase
Low acid secretion, D cells secrete somatostatin to maintain low levels of Gastrin
Cephalic Phase
dorsal vagal complex integrates input from higher centers (seeing and tasting food) to activate Vagus nerves. GRP activates gastrin release and Ach activates ECL and parietal cells.
Gastric Phase
distension of the stomach activates vagal afferents and the enteric nervous system. Amino acids activate gastrin secretion and food raises pH decreasing somatostatin secretion.
Intestinal Phase
introduction of the gastric contents into the small intestine activates duodenal G cell secretion of gastrin. Activation of secretin and other enterogastrones and neural reflex decreases secretion.
Do PPI have an effect on intrsic factor?
NO! can still absorb b12
What can cause a lack of B12 absoportion
autoimmune destriction of parietal cells, BYPASS SURGERY! can get megablastic anemia and neurological defects
What secretes pepsinogen? in response to what
chief cells, AcH and gastrin,
what inhibits pepsingen secretion?
secretin
what kind of molecule is pepsinogen
inactive prozyme proteases, activated by acid
what kind of molecule is pepsin
endopeptidase, can further activate pepsinogen by autolysis
What do surface epithelial cells secrete?
mucus and bicarb in response to PGE2
What effect does NSAIDS have on muscus seretion?
It decreases it since it blocks PGE2, this contributes to gastric irritation
What can catecholamines do to gastric mucosa?
suppress bicarb secretion, this contributes to gastric ulcers- STRESS ULCERS!
How do you regenerate disrupted epitheloum?
by using trefoil factors and growth factors
What is Zollinger Ellison Syndrome?
its a gastrin secreting tumor in the pancrease or intestine, excess H secretion as well as hyperplasia and hypertrophy of parietal cells, treat with PPi?
Peptic ulcer disease is due to?
hyperacidity, deterioration of the gastro musocsal barrier, get increase bleeding,
Some causes of gastric and duedenal ulcers
Infection – Helicobactor pylori
Poor secretion of mucus, bicarbonate by the surface epithelium
Stress (may contribute but doesn’t cause)
Irritation by alcohol, acid, digestive enzymes, bile
Tx ulcers with>
antibiotics (amoc/cipro) and proton pump inhibitor. Stop NSAID
what is the pathophysiology of peptic ulcers?
increased gastin levels because somatostain is not active in fasting state, causes increase acid, pepsin, hyperplasa of ECL cells,
Peptic ulcers in patients with hypochlohydria is related to?
gastritis and destruction of gastric epithelial cells, decrease of acid production?
Achlorhydria is due to
reduced acid secretion, caused by aging, autoimmune attack of H/K atpase, PPI, infection, atropic gastritis,
Side effects of achlorhydria?
increase bacteria growth, HIP fractures due to decrease CA, FE def anemia, decreased pep, increased diarrhea
